BMU Safety issues

[Oldpinkman]

EDIT : There appears to be no member facility to amend the title - mods, feel free
A BMU is a Balanced Mains Unit. It is a device to supply "different" mains - and in this context is for your to plug your HiFi mains plugs into. It comprises a transformer with a centre tap, which changes the normal mains supply of 0v neutral 220v live into minus 120v neutral plus 120v live.
END EDIT

Given the context in which the misunderstandings about this subject have been aired on HiFi forum, it is quite difficult to make the important point about safety without offending.

The issue regarding BMU's is not manufacturer specific.

Nor are they "dangerous"****

**** Let me heavily qualify that comment. Fireworks are not dangerous. If properly used, and properly understood.

Neither Fireworks nor BMU's are prohibited from sale or illegal. They are therefore not considered "too dangerous". However one wouldn't want to make a comment like

"A firework rocket is potentially dangerous, and should never be lit whilst held in the hand" only to have a manufacturer percieve that as an attack on their firework because they have recently launched one and make a statement in response like "it is perfectly safe to hold a rocket in your hand while lighting it. Fireworks are not illegal"

It is very obvious from reading comments on HiFi fora that BMU's are not well understood. There is that "black art" subjectivist element to them. They have a useful purpose, and can achieve a worthwhile result, but they start to acquire "magic" properties in the minds of some.

My limited expertise in this subject derives from an interest in buying one - and is the product of asking a good friend, who understands the subject properly, to explain it. I had a hum issue - earth loop of course - on the AV input to my home system only. I think a BMU might have fixed it - although in the end we fixed it at source (diferential ground on the satelite dish cable). And the BMU may have produced additional benefits by eliminating ground loop interference which was not obviously audible, but none-the-less present on the other inputs.

I looked at a BMU made by a reputable manufacturer - which retails for £340 online. It carried a number of warnings regarding its use on its web site. These included


Best used on a separate spur and not a ring
Can be used to supply incandescent lighting supplies but should not be used with other lighting supplies
Should not be used on a spur which also supplies lighting controllers
Should not be used to supply other mains conditioning products
The balance power supply should be used with a double pole switch to ensure that the equipment is fully isolated when the power is in the off position.


There was also a reference to not turning on within one minute of turning off, but this was because this supply was a bit more sophisticated than a few sockets on a transformer, and included a soft start device to avoid nuisance tripping of circuit breakers due to surge currents. (It also has surge protection and EMI/RFI filters incorporated - you must have spotted it by now!)

To shorten the story a bit, I decided it was not for me, partly because the original earth loop problem had been resolved, and partly because of some of the restrictions regarding my domestic arrangements (I wasn't prepared to start putting in dedicated spurs at this stage in the game). However, partly also as a result of my curiosity being piqued by some robust and authoratative statements being made which were counter-inutitive given my knowledge of RCD's and electromagnetism, I got my friend to thoroughly explain the subject, and address specific points raised. I learned the following points, which I think are worth sharing with others possibly interested in these devices


The reference in the warning by the manufacturer of the device referred to above, to the need for a double pole switch is because both "live" and "neutral" are "live" on a mains lead plugged into a BMU and a single pole switch might not turn off power to the hifi component. Because most hifi is made to plug into conventional domestic unbalanced mains, most hifi equipment does not have a double pole switch for its mains
A lot of hifi has fuse protection. This protection is only on the "live" rail. It will not blow and cut the current supplied on the neutral rail - because when used with normal unbalanced mains the neutral rail does not carry a voltage. This may have important implications for a Class1 device which relies on an earth connection to the case. A short of the live connection to the casework will blow the fuse. But with a balanced connection a short of the neutral rail (now carrying 110v) will not blow a fuse (although it may blow a circuit breaker on the supply to the BMU if it is a dead short). The practice adopted by some forum members building their own BMU's of fitting RCBO's to both output rails addresses this issue buy adding a "fuse" to the "neutral" supply
Domestic RCD protection will not be tripped by a short to earth on any cable or device plugged into a BMU. This is not necessarily dangerous, but it is the case. It is not hard to prove if you find the maths and physics too hard to understand (I could explain them if asked, since I learned them thoroughly). what is needed is a short to earth with a resistance high enough not to trip a circuit breaker or fuse. A lamp (inspection lamp, table lamp) is perfect. disconnect the earth wire, and connect neutral to earth. this will trip the rcd on the house plugged in to the mains direct. It should not trip the house rcd plugged into a BMU. Only use a standard incandescent bulb for this purpose. Don't play with mains if you are anything other than certain that you are safe and know what you are doing
BMU's do NOT clean the mains. They do not in anyway remove the dirt from the incoming supply. Any noise on the incoming supply will be repeated on the output supply. They do offer other benefits such as preventing further noise being added to their output supply, and potentially removing earth loop issues.



They are not illegal. They are not inappropriately dangerous. They can have a useful purpose. But they should be properly understood, as a failure to understand them might be dangerous. And making factually inaccurate statements about them is very unhelpful, and potentially dangerous.

[Joe]

Note to self: Must remember to ask my electrician to go over my accounts with me.

[walpurgis]

An explanation of what the initials BMU stand for may assist members. Also a description of what the item is, what it is intended for and where it may be of use to Hi-Fi users. Not everybody is automatically 'clued up'!

[prestonchipfryer]

What is a BMU?

[take5]

I think its an anagram for a predatory type of person, commonly found in the Hi Fi industry.

Not certain though.

[The Black Adder]

Balanced Mains Unit..?

[Oldpinkman]

I have edited my first post to the extent I can. To specifically answer "what is a BMU"

BMU stands for "Balanced Mains Unit". It is a transformer which turns normal unbalanced 220v mains into a different form of 220v mains (I am using 220v to stand for 220-240v for simplicity. The device does not voltage regulate - it voltage splits)

Instead of having live earth neutral at +240v 0v 0v it has those connections as +110v 0v -110v. The devices are widely used in the professional music market to deal with some problems caused by mains. Although those problems are more likely to be an issue in an electrically noisy environment like a studio, they can provide similar benefits in a domestic hifi installation

They are therefore sold to hifi users as a way of improving the mains supplied to equipment - and they can offer some benefits in that respect. My perception is they are viewed a bit like a "black box mains cleaner" - which supplies identical mains as the domestic socket, but cleaner. And they are very different from that. Accordingly, I think it is important to understand some of those differences.

Hope that helps

[Sovereign]

I also run a balance power supply, there is no inbuilt protection, no inrush circuit, no DC blocker not even an on / off switch. My hifi has a dedicated consumer unit with RCD protection just a few feet away. As it is only me that touches my hifi and therefor no one is going to be touching either the live or the neutral I consider it to be very safe, further to that I turn everything off after each hifi session so we are doubly safe.
Further still my hifi room is a detached brick building so if it does go up like the clappers I won't even wake up :eek:

[JohnJo]

BMUs: Would somebody please post a schematic for these showing earthing arrangements? Thanks.

[Sovereign]

I think there needs to be clarification.
A BMU is an NVA balanced mains unit and is an NVA product only. As they are glued down perspex cases a schematic is not possible unless the designer obliges.
Other balanced power supplies or BPS others use such as I use myself are slightly different. However the basic idea of a toroidial with 120v on the live and 120v on the neutral is the same.

[Ali Tait]

BMUs: Would somebody please post a schematic for these showing earthing arrangements? Thanks.

Here's the scribbled circuit I drew when I built mine-

http://imagizer.imageshack.us/v2/280x200q90/266/54242057.jpg (http://imageshack.com/f/7e54242057j)

[struth]

I think there needs to be clarification.
A BMU is an NVA balanced mains product only. As they are glued down perspex cases a schematic is not possible unless the designer obliges.
Other balanced power supplies or BPS others use such as myself and slightly different. However the basic idea of a toroidial with 120v on the live and 120v on the neutral is the same.

no its not. Russ Andrews makes them.


http://www.russandrews.com/product-BMU-1000-Balanced-Mains-Unit-1194.htm

[Ali Tait]

Photo was a bit small, this should be more ledgible-


http://i1286.photobucket.com/albums/a616/aliballybee1/BM_zpsbab224f2.jpg (http://s1286.photobucket.com/user/aliballybee1/media/BM_zpsbab224f2.jpg.html)

[Ali Tait]

Also some comment here when I took it over to Gary's-

http://theartofsound.net/forum/showthread.php?24897-Another-Motherwellshire-AOS-get-together/page3

[Sovereign]

no its not. Russ Andrews makes them.


http://www.russandrews.com/product-BMU-1000-Balanced-Mains-Unit-1194.htm

Yes mate RA and others make BPS, they are dead easy to make. The point I was trying to get across is that this thread is about BMU which is an NVA product only, although it will be almost the same as what I have made which is just a balance toroidial and nothing else. However JohnJo was asking for the schematics of a BMU, this is not possible unless NVS oblige.

[Oldpinkman]

I think there needs to be clarification.
A BMU is an NVA balanced mains unit and is an NVA product only. As they are glued down perspex cases a schematic is not possible unless the designer obliges.
Other balanced power supplies or BPS others use such as I use myself are slightly different. However the basic idea of a toroidial with 120v on the live and 120v on the neutral is the same.

If that is the case, and BMU is a trademark of NVA and not a generic term for balanced power supplies then the thread is mis-named and I apologise for the sloppy terminology. The intention is that this thread is generic about using a balanced mains supply from a "boxed solution" transformer, and NOT about any specific manufacturers product. It really should have been called "BPS" for "Balanced Power Supply" and I apologise that in the excitement of moving it from its previous (wrong) thread I was careless in my terminology.

Since manufacturers have now been named, which I was trying to avoid, the "BMU made by a reputable manufacturer" I referred to should have been a "BPS ..." and the manufacturer in question is Airlink

This is a link to the product I was considering buying http://www.airlinktransformers.com/balanced_power_supply/conditioning_balanced_power_supply/CBS2000/

This is a link to the FAQ's I referred to http://www.airlinktransformers.com/transformer-articles/balanced_power_supply_faqs/

Apologies for any confusion. This is not about NVA. Its about how this solution to mains treatment works and its implications for use in domestic environments with normal equipment

[struth]

it is called. BMU by Russ Andrews!

[Sovereign]

it is called. BMU by Russ Andrews!

OK, fair enough, my mistake. There was a thread a while again on Hifisub forum asking members to name this product , and BMU is what they came up with....what a coinsidence:scratch:

[Oldpinkman]

Yes mate RA and others make BPS, they are dead easy to make. The point I was trying to get across is that this thread is about BMU which is an NVA product only, although it will be almost the same as what I have made which is just a balance toroidial and nothing else. However JohnJo was asking for the schematics of a BMU, this is not possible unless NVS oblige.

You'll gather I am catching up with these sequentially. Russ Andrews clearly call their BPS a BMU (Balanced Mains Unit) and therefore the term is NOT referring to an NVA device. Accordingly I interpret the request for a schematic to be generic to Balanced Power Supplies and the one supplied meets the need.

You may well be right about the NVA device having some secret design element that differentiates it, but I doubt that is relevant to this discussion (if indeed it exists). As I noted elsewhere, unless it is protected by patent, it is open to anyone who wants to take the lid off. But that is not relevant. This is about balanced power supplies and not NVA

[JohnJo]

Here's the scribbled circuit I drew when I built mine-

http://imagizer.imageshack.us/v2/280x200q90/266/54242057.jpg (http://imageshack.com/f/7e54242057j)

Thanks Ali. I think there was some confusion (certainly in my head) reading other posts as some of these power supplies seem to be designed for double insulated only equipment and are a pure isolating (from earth) transformer albeit with +115/-115 balanced output and do not have the centre tapping on the secondary tied to earth and connected to the outlet sockets which is different from yours. Might build one of these myself as all my equipment is double insulated. In this type any type of RCD on the secondary would be pointless.

I don't think there is any need further protective devices (MCB or fuses) on the secondary side as there are the fuses in the 13A plugs supplying the equipment and in the back of the equipment itself and any faults in the transformer secondary winding/wiring would be seen and interrupted by the mains supply fuse on the primary, I think :scratch:

[Ali Tait]

I made mine to be portable, and to be safe to use whether the kit is double insulated or not (most is anyway).

The reason I have fitted a double pole RCBO on the secondary is that it is possible that a fault could occur on one secondary leg, but the other could still be live, for instance making the chassis of a bit of(non double insulated) kit live. I appreciate this is pretty unlikely, but I prefer to err on the side of safety, having worked in the high voltage industry for coming on 30 years now, and been to seven funereals of work collegues, some killed by some unlikely circumstances, I prefer the belt and braces approach. That's my choice, I couldn't care less what approach others wish to take. In any case, they are easy to fit, and I doubt I could hear a difference in SQ with and without, so why not fit them anyway, also you don't know what kit you may buy in the future.

Mine has been on pretty much 24/7 for coming on two years now without any issues.

[Ali Tait]

A good article here on the safety aspects-

http://www.soundonsound.com/sos/nov06/articles/crosstalk_1106.htm

[Oldpinkman]

Thanks Ali. I think there was some confusion (certainly in my head) reading other posts as some of these power supplies seem to be designed for double insulated only equipment and are a pure isolating (from earth) transformer albeit with +115/-115 balanced output and do not have the centre tapping on the secondary tied to earth and connected to the outlet sockets which is different from yours. Might build one of these myself as all my equipment is double insulated. In this type any type of RCD on the secondary would be pointless.

I don't think there is any need further protective devices (MCB or fuses) on the secondary side as there are the fuses in the 13A plugs supplying the equipment and in the back of the equipment itself and any faults in the transformer secondary winding/wiring would be seen and interrupted by the mains supply fuse on the primary, I think :scratch:

I haven't looked at every device, but the ones I have are NOT isolating - that is they do not have a floating ground, and connect ground to true earth

The fuse in your 13 amp plug won't cut the power on the neutral wire. If there is a fault that blows a fuse, there will still be 110v inside the equipment. THAT is the point about double pole switches

A dead short on the secondary ( a bit of copper shorting it) would induce such a high current in the primary that it would blow the mains supply fuse (surely these days you have circuit breaker trips). A resistive short (my incandescent bulb, a human body) might not. A 1kohm short on a 110v supply would produce only 110 milliamps of current - why would that blow a fuse?

[Oldpinkman]

A good article here on the safety aspects-

http://www.soundonsound.com/sos/nov06/articles/crosstalk_1106.htm

Unbelievable given the research I have done into this that I haven't seen that article before. Nice one Ali! ;)

[Ali Tait]

Pretty sure I've sent you that link before.. :-)

Anyway, it's a clear explanation.

[Oldpinkman]

Pretty sure I've sent you that link before.. :-)

Anyway, it's a clear explanation.

I think you're probably right :o

Probably premature senility - I think I get it from my Dad. It looks familiar now - although I think I must have only skim read it. Thanks anyway :cool:

[Ali Tait]

No worries. :-)

[JohnJo]

I see now that there is a noise cancelling function of the centre tapped earthed secondary which obviously wouldn't be there in a basic isolating tx circuit.

So, Ali's is the optimum circuit then and his use of double pole RCBO is spot on. Ali I like your belt and braces approach with electrical safety.

Very informative thread (for me) Thanks to all :)

[Oldpinkman]

I see now that there is a noise cancelling function of the centre tapped earthed secondary which obviously wouldn't be there in a basic isolating tx circuit.

So, Ali's is the optimum circuit then and his use of double pole RCBO is spot on. Ali I like your belt and braces approach with electrical safety.

Very informative thread (for me) Thanks to all :)

Johnjo - be careful about this noise cancelling. It is probably of little use in a domestic situation. THE DEVICE DOES NOT CANCEL NOISE ON THE MAINS. It cancels any extra noise added to the mains on the lead between the BPS and the HiFi appliance ONLY. However, not only is that noise likely to be insignificant, if it exists at all, the same noise would be added to the lead from the BPS to the wall socket AND NOT CANCELLED BY THE BPS. So the net gain is NIL. In the unlikely event that there is any environmental noise to be added to a cable in the room, without a BPS it will be added to the cable from the Hifi to the wall, and with a BPS IDENTICAL NOISE would be added to the cable from the BPS to the wall AND NOT CANCELLED.

This is of potential value in professional studios where you can have a short cable from the BPS to the wall, but long cable runs from the BPS to the appliance - but it is not the main reason for their use. Personally (having made the same mistake until it was carefully explained to me) I think people get hold of the wrong end of the stick about balanced connections and noise cancellation.

It is identical to a balanced signal connection. The balanced connection prevents noise being added to the signal cable - IT DOES NOT REMOVE ANY NOISE FROM THE INPUT TO THAT CABLE. This is far more valuable with signal cables where the signals are very low level, the cable runs are long, and the environmental noise potentially proportionately quite high. It is arguable whether it is of any real benefit in the context of a mains cable - but if it is, it would only be so in the context of VERY long cables to the equipment, relative to a short cable to the BPS.

And it has nothing to do with the way noise cancelling headphones work (it happens the "mate" I refer to was one of the early pioneers of noise cancelling at Essex Uni, subsequently developing commercial systems in Arizona)

Hope that helps even more :)

[Ali Tait]

It doesn't change the fact that it seems to make a real improvement to the sound of a system. In Gary's system, it totally transformed the sound, an amazing improvement akin to plugging in a totally different system, so they certainly do something!

[Ali Tait]

Wiki article-
http://en.wikipedia.org/wiki/Balanced_circuit

[Oldpinkman]

Ali - for sure they may assist with earth loop issues - but as the article you posted points out there are other ways to deal with those.

But the purpose of this thread is not to oppose anybodies subjective appreciation of the benefits of the device - it is to emphasise the risk of fatality from mis-understandings about the nature of the device, and as a minor sideshow share my learning about how they work and correct the misunderstanding about the nature of a balanced connection.

I might see if I can get Owen to build one, see if we can hear any difference, and if we can (subjectivists cover your ears here) try to measure what it is that causes the difference. I'm intrigued. If it makes a difference, once we move to France and I can attend to the wiring (and will have radial spurs anyway) I might give one a go. Fitted with RCBO's on the output!!!!! :cool:

[Oldpinkman]

If anyone is interested in a technical explanation of how a balanced connection works and why it doesn't cancel noise, and is bored of the sound of my voice - Barry has in the past provided me with a very helpful explanation. Ask the Oracle! ;)

[awkwardbydesign]

If anyone is interested in a technical explanation of how a balanced connection works and why it doesn't cancel noise, and is bored of the sound of my voice - Barry has in the past provided me with a very helpful explanation. Ask the Oracle! ;)

Personally, I have found your explanations helpful.

[Ali Tait]

Ali - for sure they may assist with earth loop issues - but as the article you posted points out there are other ways to deal with those.

But the purpose of this thread is not to oppose anybodies subjective appreciation of the benefits of the device - it is to emphasise the risk of fatality from mis-understandings about the nature of the device, and as a minor sideshow share my learning about how they work and correct the misunderstanding about the nature of a balanced connection.

I might see if I can get Owen to build one, see if we can hear any difference, and if we can (subjectivists cover your ears here) try to measure what it is that causes the difference. I'm intrigued. If it makes a difference, once we move to France and I can attend to the wiring (and will have radial spurs anyway) I might give one a go. Fitted with RCBO's on the output!!!!! :cool:

I'd be interested in the results.

[JohnJo]

Johnjo - be careful about this noise cancelling. It is probably of little use in a domestic situation. THE DEVICE DOES NOT CANCEL NOISE ON THE MAINS. It cancels any extra noise added to the mains on the lead between the BPS and the HiFi appliance ONLY. However, not only is that noise likely to be insignificant, if it exists at all, the same noise would be added to the lead from the BPS to the wall socket AND NOT CANCELLED BY THE BPS. So the net gain is NIL. In the unlikely event that there is any environmental noise to be added to a cable in the room, without a BPS it will be added to the cable from the Hifi to the wall, and with a BPS IDENTICAL NOISE would be added to the cable from the BPS to the wall AND NOT CANCELLED.

This is of potential value in professional studios where you can have a short cable from the BPS to the wall, but long cable runs from the BPS to the appliance - but it is not the main reason for their use. Personally (having made the same mistake until it was carefully explained to me) I think people get hold of the wrong end of the stick about balanced connections and noise cancellation.

It is identical to a balanced signal connection. The balanced connection prevents noise being added to the signal cable - IT DOES NOT REMOVE ANY NOISE FROM THE INPUT TO THAT CABLE. This is far more valuable with signal cables where the signals are very low level, the cable runs are long, and the environmental noise potentially proportionately quite high. It is arguable whether it is of any real benefit in the context of a mains cable - but if it is, it would only be so in the context of VERY long cables to the equipment, relative to a short cable to the BPS.

And it has nothing to do with the way noise cancelling headphones work (it happens the "mate" I refer to was one of the early pioneers of noise cancelling at Essex Uni, subsequently developing commercial systems in Arizona)

Hope that helps even more :)

Sorry Richard, I meant cancels noise from the load (hifi).

[Oldpinkman]

Sorry Richard, I meant cancels noise from the load (hifi).

I'm not quite sure what you mean by that. But I think that it may be you are looking for something the device doesn't achieve.

The only noise that gets cancelled - by the operation of the balanced connection - is external noise imposed on the cable between the BPS and the "load". But as I pointed out - if any such noise is present in the environment - it will be added to the cable connecting the BPS and the wall socket, and that noise will not be cancelled or removed by the balanced connection and will be the same as the noise that would have been there anyway without the BPS.

Hum (which is one form of noise) may be removed by virtue of the earth loop lifting.

Hold onto your hats - lets do some algebra.

First - take a look at this link which is my favourite basic introduction to the subject https://www.youtube.com/watch?v=jo5HhfIUSP0

Using their equation lets add another element. We now have the signal S(110v) and 180 degree inverted signal -S(-110v)
There are 2 sorts of noise. Noise on the mains coming into the device, via the lead between the wall and the BPS, including all the noise on the ring or spur, consumer unit etc etc) Big N
Then there is noise which affects the connection between the BPS and the Hifi - little n

Big N will also be split into a phase and out of phase component

So we get S+N as one component, and -S-N as the other "phase". To this we add noise of n

The equation now reads (S+N+n)-(-S-N+n) =

S+N+n+S+N-n = 2S+2N

S in this case was 110v, so 2S=240v. N hasn't got bigger. It was 2N before it was split, like the incoming voltage was 2S before it was split

But the only noise you lose is little n. BIG N - the noise that is in the mains supply and connection to the BPS is still there on the output

Simples ;)

Hold on tight now. Whilst little n has been usefully eliminated in this example, remember that it was part of BIG N on the connection from the BPS to the wall. Without that connection, BIG N would have been smaller by little n.

So the noise coming into the HIFI without a BPS would have N-n (The noise without the cable from the BPS to the wall) PLUS n the noise on the cable from the HIFI to the wall. (N-n)+n = N which is the same as with the BPU

Don't you just love sums? :eek:

[Gordon Steadman]

Don't you just love sums? :eek:

No:(

[awkwardbydesign]

Don't you just love sums? :eek:
My wife left school when she was 14; she turned 15 in the summer holidays so started work immediately. Her school didn't do maths; it was arithmetic! :lol:

[Oldpinkman]

I appreciate not everyone likes sums. It's what I have to cope with talking to Owen who sees everything in maths.

That was a mathematical proof that a BPS / BMU does NOT remove noise (N) from mains. I can see not everyone will love me for that. (My wife would glaze over). So to simplify the same point

The BPS like a balanced signal connection applies its balancing magic to the connection. The interconnect from CD player to amp in the case of a balanced signal connection. The connection between the BPS and the HiFi in the case of the BPS.

It doesn't change what comes into it.

Big N - the noise we are trying to get rid of - is just part of the signal as far as the BPS is concerned and so it leaves it alone, in the same way a balanced interconnect doesn't start filtering bits out of the music fed to it.

Was that better Gordon?

:cool:

[Gordon Steadman]

I appreciate not everyone likes sums. It's what I have to cope with talking to Owen who sees everything in maths.

That was a mathematical proof that a BPS / BMU does NOT remove noise (N) from mains. I can see not everyone will love me for that. (My wife would glaze over). So to simplify the same point

The BPS like a balanced signal connection applies its balancing magic to the connection. The interconnect from CD player to amp in the case of a balanced signal connection. The connection between the BPS and the HiFi in the case of the BPS.

It doesn't change what comes into it.

Big N - the noise we are trying to get rid of - is just part of the signal as far as the BPS is concerned and so it leaves it alone, in the same way a balanced interconnect doesn't start filtering bits out of the music fed to it.

Was that better Gordon?

:cool:

Nah - not really.

I just bung something on the hi-fi and listen to the music. All this technical malarky I find as interesting as bits of wire and hocus pocus.

I do however, appreciate that someone has to be interested in how things work.

[prestonchipfryer]

I'm not quite sure what you mean by that. But I think that it may be you are looking for something the device doesn't achieve.

The only noise that gets cancelled - by the operation of the balanced connection - is external noise imposed on the cable between the BPS and the "load". But as I pointed out - if any such noise is present in the environment - it will be added to the cable connecting the BPS and the wall socket, and that noise will not be cancelled or removed by the balanced connection and will be the same as the noise that would have been there anyway without the BPS.

Hum (which is one form of noise) may be removed by virtue of the earth loop lifting.

Hold onto your hats - lets do some algebra.

First - take a look at this link which is my favourite basic introduction to the subject https://www.youtube.com/watch?v=jo5HhfIUSP0

Using their equation lets add another element. We now have the signal S(110v) and 180 degree inverted signal -S(-110v)
There are 2 sorts of noise. Noise on the mains coming into the device, via the lead between the wall and the BPS, including all the noise on the ring or spur, consumer unit etc etc) Big N
Then there is noise which affects the connection between the BPS and the Hifi - little n

Big N will also be split into a phase and out of phase component

So we get S+N as one component, and -S-N as the other "phase". To this we add noise of n

The equation now reads (S+N+n)-(-S-N+n) =

S+N+n+S+N-n = 2S+2N

S in this case was 110v, so 2S=240v. N hasn't got bigger. It was 2N before it was split, like the incoming voltage was 2S before it was split

But the only noise you lose is little n. BIG N - the noise that is in the mains supply and connection to the BPS is still there on the output

Simples ;)

Hold on tight now. Whilst little n has been usefully eliminated in this example, remember that it was part of BIG N on the connection from the BPS to the wall. Without that connection, BIG N would have been smaller by little n.

So the noise coming into the HIFI without a BPS would have N-n (The noise without the cable from the BPS to the wall) PLUS n the noise on the cable from the HIFI to the wall. (N-n)+n = N which is the same as with the BPU

Don't you just love sums? :eek:




My maths teacher at school (1960s) said that one day algebra could be useful to me. But today isn't the day. :lol:

[walpurgis]

My maths teacher at school (1960s) said that one day algebra could be useful to me. But today isn't the day. :lol:

Funny. I was told much the same (about the same time too). Not had a use for quadratic equations yet. :D

[Oldpinkman]

I remember hugely impressing my missus - who very much takes the same view about maths at school being useless, when I worked out how long a piece of coiled pipe, which we didn't want to uncoil was based on the number of coils and Pi times the diameter. And when we did uncoil it (after moving it) she found my answer was right. :)

[Marco]

Yes, but did it get you a shag? ;)

Marco.

[struth]

My maths teacher at school (1960s) said that one day algebra could be useful to me. But today isn't the day. :lol:

Mine said it would be of little help to me when I am sweeping the streets....Wank! I ended up his missus's boss lol:eyebrows:

[Oldpinkman]

Yes, but did it get you a shag? ;)

Marco.

No it was my winning smile did that . :eyebrows:

[walpurgis]

Mine said it would be of little help to me when I am sweeping the streets....:eyebrows:

Have you still got the broom Grant? :D

[struth]

Have you still got the broom Grant? :D


No, I gave him it back Geoff :eyebrows:

[Sovereign]

Ali -

I might see if I can get Owen to build one, see if we can hear any difference, and if we can (subjectivists cover your ears here) try to measure what it is that causes the difference. I'm intrigued. If it makes a difference, once we move to France and I can attend to the wiring (and will have radial spurs anyway) I might give one a go. Fitted with RCBO's on the output!!!!! :cool:
Or as you live down the road , I could bring mine over.

[Oldpinkman]

Or as you live down the road , I could bring mine over.

I thought I'd bring my dodgy inspection lamp with neutral wired to earth over to your hifi nuclear bunker for testing where it wouldn't take out the whole house. We had 2 nuisance trips in a week last week. I was on the verge of calling my electrician friend to convert my consumer unit from rcd and mcbs to an rcbo board yet again. It's been on the "to do" list for a couple of years now - but put off (like the 2 flat roofs I have been compelled to fix this month) in the hope we can move to France first.


Currently I use multiways with surge protection and the airlink site would have me believe they are not appropriate with a bmu. How many socket outlets does it have? Or would you try it on just one bit of kit? Also the supply is the downstairs ring which has lighting controllers on it too (although we could avoid using them while testing). Maybe try your nuclear bunker first. :)

[Sovereign]

I thought I'd bring my dodgy inspection lamp with neutral wired to earth over to your hifi nuclear bunker for testing where it wouldn't take out the whole house. We had 2 nuisance trips in a week last week. I was on the verge of calling my electrician friend to convert my consumer unit from rcd and mcbs to an rcbo board yet again. It's been on the "to do" list for a couple of years now - but put off (like the 2 flat roofs I have been compelled to fix this month) in the hope we can move to France first.


Currently I use multiways with surge protection and the airlink site would have me believe they are not appropriate with a bmu. How many socket outlets does it have? Or would you try it on just one bit of kit? Also the supply is the downstairs ring which has lighting controllers on it too (although we could avoid using them while testing). Maybe try your nuclear bunker first. :)

It has Neutrik power connectors on it, but I could lash up a double A double socket onto it for you, it it were me I would run your whole hifi off the BPS then see what you think.

[Oldpinkman]

It has Neutrik power connectors on it, but I could lash up a double A double socket onto it for you, it it were me I would run your whole hifi off the BPS then see what you think.

(from the Airlink Q&A)

Question 6) Can a three socket extension lead be used from one of the outputs?

Answer: This is not recommended as the extension lead would introduce several unwanted impedances between the BPS and the equipment and a degree of unbalance.

Question 2) As part of the same spur/ ring main, can technical balanced power be combined with unbalanced mains to be used for desktop lighting - in other words one wall socket will feed the CBS2000 and the other will power lamps.

Answer: although the units are ok for use with incandescent lamps, there may be problems with other forms of lighting.
Balanced PSU’s should not be fed from spurs supplying lighting controllers

Question 3) Can the unit feed one or more rack mount power conditioning units such as those by Furman. The Furman units have spike suppression systems and RFI/EMI filtering built in. Would the spike suppressor and filtering on the CBS2000 interfere in any way with the Furmans, or visa versa.

Answer: The balance PSU should not be used to feed other mains conditioning units, under no-load & light load conditions excessively high supply voltages could be generated, possibly damaging connected equipment

My existing set up would risk running foul of all of those :( The man wot nose should be back from Arizona soon - mind his view is a properly designed amplifier shouldn't mind what mains its fed ;)

[Sovereign]

You will just have to swing by my place in Loose , the wine is extra fruity this end of town ;-)

[Ali Tait]

I would wire in your extension socket as a ring from one socket to the other (assuming two on the unit). However, I built mine with a double unswitched mains socket, one feeds a long steel extension screwed to the back of my rack, and the the other feeds a Belkin PF40, which feeds most of my kit, so for the last two years I've been doing two things Airlink don't recommend with no problems.

[Sovereign]

I used to run my old BPS into a AG1500 regenerator with no problems at all, both live and neutral were perfectly balanced. Ali I think I even measured this while i had you on the phone.
Speaking with Power Inspired last week, they advised the two should be installed the other way round ie. regen first then the BPS. I never tried it this way, and I no longer have a regen to try. All I have now is a much higher quality BPS, I didn't realise the difference a higher quality BPS would make compared to the ones I previously had from Airlink.
My old BPS was wired with sockets in a ring formation like you suggest Ali, with no loss of balance or performance.

[Ali Tait]

Haven't tried that myself, though it would mean running the whole system from one outlet on the Belkin, which I don't think would be a good idea, unless I parallelled up some of the sockets inside to get the required current delivery. Probably easier to fit a filtered IEC socket to the balanced mains box to feed it with- I put an IEC on mine so it could be portable.

[Oldpinkman]

I think mention of the wine swings it for the nuclear bunker James. I can bring a bottle. If its really exciting I'll start working out how to do it here, though as I say, I have a "just camping" mentality atm, and probably won't do anything elaborate before France

(Except switch to RCBO's if we start getting too many nuisance trips. As i point out to my wife when she asks why we don't get "it" checked properly. For the whole of a year bar 2 separate one second moments there is nothing wrong with "it" or the RCD's wouldn't set. It's very difficult to carry out any tests during those 2 seconds of "fault" condition. But RCBO's would mean only the offending circuit going down and not the whole bloody house - just when I'm in the middle of important work. I was driven to doing everything on a laptop one January) :steam:

[Sovereign]

I run a building and maintenance business, if you want any help what ever it may be then just shout.
I'm free tonight, or next week except Wednesday or Thursday.

[brian2957]

Can you come over and have a look at mines too James . I'm free Monday and Tuesday . I'll get the strawberry tarts in :D

[Sovereign]

SOD & OFF

[brian2957]

Hah ! That's a terrible way to speak to a prospective customer :lol:

And to think i was gonna buy you a strawberry tart . Well that won't be happening now :ner:

[Sovereign]

Glasgow is a great place. Glasgow is actually my roots. Maybe that's why I like rough women

[brian2957]

I just put Glasgow down for convenience . I actually live about 15 miles from the city centre and about 30 miles from Edinburgh . I very seldom visit Glasgow James , too many people in the one place for my liking :lol:

[Sovereign]

I've heard the women are rougher the further away from Glasgow you go?

[brian2957]

:lol::lol: How did I know you were gonna say that . The wife wants to know what I'm laughing at :lol: I thought I'd better keep my mouth shut :D

[Sovereign]

Or she may club you!
This is turning into a soft porn thread.

[brian2957]

I quite like a good clubbing mate :eyebrows: Better stop there eh ! :lol:

Just looking at your signature mate . Your system hasn't half changes in recent times . Any photos ? Did you build the DAC yourself . Got a link ?

[Sovereign]

I know massive change, and very very much for the better, I must update my system thread in the Gallery section. Its changing again as I'm about to upgrade my Lampizator OB's from P17s to P23s, and I have a have a Stereo Coffee LDR pre amp here on loan, which I am blown away with, so I plan to build one of this as well.
Here is a link to the DDDAC
http://www.dddac.com

[brian2957]

I'll have a proper look later James , but initial impressions are far too technical for me mate . I love OBs , I've heard Ali Taits a few times and I really like what they do , again a bit beyond me though .

[Sovereign]

I'm not technical at all, but if someone gives me the recipe I can bake a cake

[brian2957]

Food for thought mate ( excuse the pun ) . I'll see when I have had a proper look . Thanks though .

[Sovereign]

Or this one
http://www.diyaudio.com/forums/digital-line-level/224108-nos-192-24-dac-pcm1794-waveio-usb-input.html

[brian2957]

Jeez mate , this is way above my head . Think I'll stick to pre- baked cakes ( and DACs ) .

[Gazjam]

Seems a good point to mention my BPS install thread, could be useful for some folks.
http://theartofsound.net/forum/showthread.php?26471-Balanced-Mains-Transformer-WOW!-Hardwired-Installation-log-%28Pic-Heavy!%29&highlight=balanced+mains+gazjam

For my own install, I've 10mm CSA spur cable coming from BPS main output terminals feeding a "hydra" junction box.
All my kit is hardwired to this, except anything with a switching supply which is plugged into a Belkin PF 30 mains conditioner....again, hardwired to the hydra.

[Oldpinkman]

Thanks Gary

Excellent that your thread emphasises the safety aspects, and your installation benefits from the RCBO's on the output, which is essential if you want to maintain RCD protection on any devices connected to a BPS, and essential if you want a fuse protection for the neutral supply to any connected device.

Just to really hammer this safety point home, the only aspect you don't really mention is that the use of a BPS means that any device connected to it which has a normal single pole switch, will not be properly switched off using that. you need to either add a dual pole switch inline to the appliance, or turn off the power at the BPS itself, to completely turn off power to the device.

Moreover, if your appliance is fitted with a fuse inside the chassis, this will only be on the live supply and since the neutral supply is now live too, you would need to fit a fuse on that connection inside the chassis too, to maintain equivalent protection. The RCBO current overload rating is likely to be much higher than the internal fuse rating on most equipment.

Keep safe when modifying mains! is the message. :)

[Sovereign]

Keep safe when modifying mains! is the message. :)
You better wear your rubber boots when you come to Sovereign Towers mate:stalks:

[Oldpinkman]

Following the popular acclaim for my maths lesson, I thought it might help to explain why an RCD needs fitting to the output of a BPS if you want to keep the protection of an RCD for any devices connected to it.

Or put another way, why a BPS acts to bypass the safety protection of an RCD on the main household consumer board.

The following link is a nice explanation of how RCD's work, with an animation which I find makes it particularly clear http://www.explainthatstuff.com/howrcdswork.html

The animation shows scissors cutting one of the wires, but more normally a connection is made to earth on one of the wires only (say by an earthed human touching it - that is what they are designed to protect. ) The connection to earth on one wire means some of the current flows down that connection, and so less of it flows along the remainder of the wire into the RCD - creating the imbalance.

A BPS uses a transformer to ISOLATE the output side physically from the input to it. The 2 sides are still connected, but only electromagnetically. When a circuit is made on the output (you switch something on) a current flows through the output coils of the transformer (called the secondary) and this causes a current to flow in the input coils (called the primary). If you short one of the connections on the secondary to earth, then there will be an unequal current flowing in the 2 wires in the secondary. An RCD fitted on the secondary supply (output) would detect this in the normal way. But regardless of where the current is flowing in the secondary, it still creates a current in the primary, and that current will flow equally in both the connections to the primary . The only way you can get a different current flowing in the live wire of the primary to that flowing in the neutral wire in the primary, and so trip an RCD on the primary, is to physically make a connection to one of the primary wires and not the other - and that can't happen if the earth leak is only on the secondary.

Gazjams protection goes one better, because he uses an RCBO. This is a combination of a miniature circuit breaker (MCB) and an RCD in one device. The MCB uses electromagnetics and a relay to cut power if too much current flows down its wire - regardless of whether that is equal in both wires or not. Its like a resetable fuse. The devices used by Gazjam and Ali have detection on both of the connections - so its like having a fuse on the live wire and a fuse on the neutral wire.

However - although you have 3 separate devices in a dual rail RCBO (RCD, live "fuse" and neutral "fuse") there is only one reset button for all of them, so normally no way to know which of the 3 devices "tripped".

If the fault on the secondary causes a very high current to flow in it (like a dead copper wire short) then that would cause a very high current to flow in the primary - and blow the fuses in the primary (or the "fuse" parts of an RCBO)

But that is not the same protection as the RCD would provide - which is tripped by much smaller currents.

Here endeth todays lesson ;)

[Sovereign]

I still don't see the point in all this.
Not the BPS I have now, but the one I made before this I tool Ali T's advice and had it wired up as his diagram shows. However there is only me who ever uses my hifi, I turn it off at the consumer unit when I'm finished and I don't go near mains cables with knives , scissors or crocodiles

[Oldpinkman]

I still don't see the point in all this.
Not the BPS I have now, but the one I made before this I tool Ali T's advice and had it wired up as his diagram shows. However there is only me who ever uses my hifi, I turn it off at the consumer unit when I'm finished and I don't go near mains cables with knives , scissors or crocodiles

I think that's not unreasonable. There is no requirement to have RCD's. They are more useful if you are drying your hair in the bath or cutting the hedge in the rain than listening to HiFi. Some Consumer boards only fit RCD protection to the downstairs garden circuits. The issue is not so much that you MUST have RCD's - it is that if you do choose to have that sort of protection you need to realise that a BPS will bypass it. If you have a house with an old Consumer board and wire fuses the point would be academic.

Likewise half this forum never turn off the side of their equipment the fuse and single pole switch works on. But the point to emphasise is that you need to appreciate what is the same and what is different. Not pretend that something will work when it won't.

And you just never know when the water tank located over your HiFi (as mine was until 7 years ago) is going to burst, or a radiator pipe burst, or a lorry drive through your living room wall (Tonbridge A227 corner of East Street about 8 years ago) - never mind toddlers pulling TV's off shelves by the cable (my twin godsons), dogs chewing through cables even though they've never chewed before (my senile 16 year old mongrel)...

Obviously not in your nuclear bunker, where we listen in our wellies, but in the real world

:cool:

Edit : Oh - and you should live in a village that floods higher than the hifi shelf every few years... ;)

[Gazjam]

wot Oldpinkman said...safety first.

Do your homework and decide if you are happy with the (however unlikely) risks.
If you've double pole RCBO's at primary and secondary you''ll be fine.

Heard that from someone who has 30+ years installing multi KV power stations...
compared to my hifi...?
I'm happy with that.


Thanks Gary

Excellent that your thread emphasises the safety aspects, and your installation benefits from the RCBO's on the output, which is essential if you want to maintain RCD protection on any devices connected to a BPS, and essential if you want a fuse protection for the neutral supply to any connected device.

Just to really hammer this safety point home, the only aspect you don't really mention is that the use of a BPS means that any device connected to it which has a normal single pole switch, will not be properly switched off using that. you need to either add a dual pole switch inline to the appliance, or turn off the power at the BPS itself, to completely turn off power to the device.

Moreover, if your appliance is fitted with a fuse inside the chassis, this will only be on the live supply and since the neutral supply is now live too, you would need to fit a fuse on that connection inside the chassis too, to maintain equivalent protection. The RCBO current overload rating is likely to be much higher than the internal fuse rating on most equipment.

Keep safe when modifying mains! is the message. :)

[Sovereign]

If definitely not knocking Ali at all, as I have often said I'm not technical or hugely experienced. I just take advice from others.
However my hifi isn't below a header tank, my listening room will not have a lorry driving through it as its in the back garden down a one way leafy lane, I don't have a dog that mistakes mains cables for a bone, or a child that will pull my hifi apart or a garden that will flood. Thats not to say that others don't, as many peoples hifi are in their living rooms as mine was in my old house.
HOWEVER, thats not to say I haven't had my fair share of bolts. 2 years ago, before my hifi had its own CU it was running from the downstairs ring main. The wife was upstairs in the bath so I turned off the downstairs RCD and started messing around with my hifi mains. The wife came downstairs, saw the clock to the microwave and oven were not on, went to the CU and flicked the RCD back on. And pop I went.
Nothing was as bad as when I was working in the states and got a very very nasty bolt from a 3 phase board! that kicked me back a few feet.

[Oldpinkman]

I worked as a student cleaning the toilets at Darenth Park Mental hospital. A job I could have done on my own in 3 hours, but took 3 of us all day, with union required tea breaks etc.
Not helped by one of the team of 3 suffering the effects of a bad electrocution which left him mentally disabled (and physically handicapped) for life.


I also run a balance power supply, there is no inbuilt protection, no inrush circuit, no DC blocker not even an on / off switch. My hifi has a dedicated consumer unit with RCD protection just a few feet away. As it is only me that touches my hifi and therefor no one is going to be touching either the live or the neutral I consider it to be very safe, further to that I turn everything off after each hifi session so we are doubly safe.
Further still my hifi room is a detached brick building so if it does go up like the clappers I won't even wake up :eek:

So - the bunker is a safe place with no need for protection. WTF were you doing fitting an RCD to its supply, only to bypass the thing for every device in the room connected to a BPS which renders the RCD pointless :scratch:

[Gazjam]

Funny.. :)

Things CAN happen though, and you need to decide if that "walk out my door and get hit by a bus" mentality is the thing that will determine how good you will feel going about your day.

Regarding Balanced Mains Systems....
Double Pole RCBO on both Primary and Secondary and job's a good 'un IMO (and others that know what they are talking about)
I've also been that guy who second guesses everything, and sometimes, you know, there's just some people that know more than you?
Do what they say and stop worrying!

that works for me, what other people want to do is their business :)

[Oldpinkman]

(I should note James and I are planning to get together on Monday so there is a backdrop to this banter)

It is however just this sort of muddled thinking that is the reason for this thread. By all means go without RCD protection. But don't fit an RCD, then bypass it and render it useless by connecting everything in the room to a BPS, and think you have protection. One thing or the other :)

[Sovereign]

I know what your saying but the new cu was fitted by an NIC EIC electrician and it of course had to meet 17th edition regs to be signed off.

[Ali Tait]

Just to put things in a bit of perspective and make a couple of points clear, yes, I accept that it's unlikely that there could be a problem in using a BPS without any secondary protection. Nevertheless, a risk exists. I also accept that there is no risk of electrocution from the case of a double insulated BPS without any secondary protection- that's obvious.

My BPS is made with a metal electrical enclosure, but that is NOT why I fitted the secondary protection. The transformer is fitted in such a fashion that it is isolated from the case, but, I have both the enclosure and it's door hard wired to the incoming mains earth, so any fault within the enclosure will trip the CU.

Protection was fitted on both the primary and secondaries for a couple of reasons-

1. I wanted a portable BPS, and given it could be used in a variety of situations, I needed to ensure it could be used safely in any of them.
2. I have a variety of kit in my system, including a Garrard 401, which is most definitely not double insulated, amongst other things that aren't either. Furthermore, who knows what I'll purchase in the future, so again I wanted something that can be safely used with anything.

What other folk do is up to them. For myself, I prefer to ensure maximum safety. Given my job, training and proclivities, I could not do otherwise.

[Sovereign]

Your right Ali, I'm never nocking safety or people's experience, as mine is limited, that's why I'm often trying to learn from others, hence the odd email.
Mine is not really portable at all, I took it to Steve's house, Electricbeach, and I couldn't use it as it has no inrush protection. To be fair it was more due to his crappy mains, as he still has an old brown Wylex fuse board. Plug in my 3kVa BPS with no inrush protection and there is no way his fuse board would cope. It would have been ok with a modern consumer unit as mine is fine.

[Ali Tait]

Aye, I had problems here before fitting the limiter, was fine on a socket connected to the ring, but there is a dedicated radial for an electric fire which had never been used, ideal to feed the system. Plugging in the BPS tripped the breaker in the CU every time. Fine with the limiter though.

As for the safety thing, not knocking what other folk do either, but I've been to seven funerals of work colleagues over the years who were killed at work. Tends to focus the mind on safety!

[Barry]

Your right Ali, I'm never nocking safety or people's experience, as mine is limited, that's why I'm often trying to learn from others, hence the odd email.
Mine is not really portable at all, I took it to Steve's house, Electricbeach, and I couldn't use it as it has no inrush protection. To be fair it was more due to his crappy mains, as he still has an old brown Wylex fuse board. Plug in my 3kVa BPS with no inrush protection and there is no way his fuse board would cope. It would have been ok with a modern consumer unit as mine is fine.

Is the inrush current of your BPS > 30A (which would blow the 15A fuse protecting a radial circuit), or > 60A (which would be needed to blow a 30A fuse protecting a ring main)?

[Ali Tait]

Good point, I'd expect an old fuse board like that to cope better than a modern CU.

[Sovereign]

Good point, I'd expect an old fuse board like that to cope better than a modern CU.

That's where my knowledge is limited. However is a breaker trips then it's easy to re set, if a fuse blows it's a pain in the arse to re wire

[Ali Tait]

There is that!

[Barry]

My house still uses a (MEM) fuse box. No fuse has ever blown in the 35 years I have lived here.

I once fitted a Wylex consumer unit in my parents house, fitted with over-current circuit breakers. The 5A rated breaker, protecting the lighting circuit, would often trip out if an incandescent light bulb blew on switch on. :doh:

[Mr Kipling]

What is a BMU?

I thought it was a film following the exploits of three individuals questing for buried treasure:

The Bad, The Mad And The Ugly

MAJOR PUBLIC HEALTH WARNING:

ON NO ACCOUNT, REPEAT ON NO ACCOUNT, WHATSOEVER, NEVER EVER, EVER, bend down to pick up teacake fallen from the shelf at your local supermarket without wearing the appropriate PPE (Personal Protective Equipment). Doing so, could result in the currant shooting up your arm.

I don't quite understand why such a device is now being seen as a potential death-trap. It's not exactly a radical new concept. Or why this thread has managed to get to 10 pages…

[Ali Tait]

My house still uses a (MEM) fuse box. No fuse has ever blown in the 35 years I have lived here.

I once fitted a Wylex consumer unit in my parents house, fitted with over current circuit breakers. The 5A rated braker, protecting the lighting circuit, would often trip out if an incandescent light bulb blew on switch on. :doh:

That still happens, but I guess it's better to err on the side of caution..

[Beobloke]

I know what your saying but the new cu was fitted by an NIC EIC electrician and it of course had to meet 17th edition regs to be signed off.

Sadly, in my experience this doesn't mean a great deal sometimes. The electrics in the new kitchen in our old house were also installed and signed off by fully qualified electricians. It took nearly a year for the completely unsecured junction box behind the dishwasher to allow the cable to gradually melt with the heat, short circuit live and neutral, fill the kitchen with smoke, trip the RCBO and melt part of the fuseholder in the fused switch on the worktop.

I repaired it to a standard I was happy with and which was probably overkill, however working daily with voltages in the region of 3kV makes you quite cautious...

[Ali Tait]

It does indeed.

[Ali Tait]

Whatever happened to tradesmen who actually give a shit about what they do?

They seem very thin on the ground these days.

[struth]

Even my shed has a full blown fuse box with trip fuses just in case, connected to the house with armoured cable run underground...

[Sovereign]

Is the inrush current of your BPS > 30A (which would blow the 15A fuse protecting a radial circuit), or > 60A (which would be needed to blow a 30A fuse protecting a ring main)?

Sorry I missed this one.

The peak inrush current can vary anywhere between 80mA to over 1000A for 20-60 milliseconds. It’s a pure gamble and depends at what points in the sinewave the transformer is switched off & again what point of the sinewave the transformer is switched back on

[Oldpinkman]

Well - a most enjoyable trip to James (Sovereign) nuclear bunker. No BPS testing carried out, partly cos we were busy listening to music and chatting, and mostly because I don't think we had a common connector between the pair of us, including mains plugs. And I didn't fancy trying to wire up my dodgy angle-poise with the firemans hose cables James uses.

So any youtube videos of a BPS isolating the RCD's on the primary will have to wait till I get a unit with conventional mains sockets on. Or an adaptor. And, by preference, if I carry out the test here, the consumer unit converted to RCBO's, because however much I try to isolate using a portable RCD plug its a 50:50 call whether that or the house main RCD blows first, and its a real pain having to reset the whole house every time. May have to treat myself to a PAT test isolator - or borrow Scotties.

Meantime - I felt very old. James had warned me he didn't have vinyl - but I thought we could play CD's (we did by ripping them to the Macbook first). A very enjoyable evenings listening - very different to the presentation I am used to on my system. I think James when he comes round may find my system "ethereal" to the point of weedy. And we will face the lack of common connector challenge (my Dacapo only has toslink, BNC and balanced sockets - James only uses USB) :doh:

Also very jealous - James has a 24/7 listening room, where I have to operate a 9PM curfew out of consideration for the neighbours.

Happily, whilst we appeared not to have a compatible component to swap in sight, we had a good deal more in common when it came to music, so a very enjoyable and informative listening session instead.

And I got to see my first NVA amplifier in the flesh, as well as an LDR passive and a BPS.

Thanks James - my gaff next time

:cool:

[worrasf]

Just my two penneth from observation.

I have a BMS (one of these http://www.airlinktransformers.com/balanced_power_supply/standard_balanced_power_supplies/BPS3120/) which is in the loft. Was fitted when the sparkie installed a new CSU and electrics for an extension at home.

This is run from a dedicated spur from a new CSU with a single RCD for this circuit only.

The BMS is used only to run all my HiFi stuff.

If I have a senior moment and connect a bit of kit (DVD player for example) which runs on the standard house mains with a coax to the preamp on the BMS then the RCD at the consumer instantly trips the BMS transformer. No issue (obviously) if I use optical connect.

Steve

[Oldpinkman]

Just my two penneth from observation.

I have a BMS (one of these http://www.airlinktransformers.com/balanced_power_supply/standard_balanced_power_supplies/BPS3120/) which is in the loft. Was fitted when the sparkie installed a new CSU and electrics for an extension at home.

This is run from a dedicated spur from a new CSU with a single RCD for this circuit only.

The BMS is used only to run all my HiFi stuff.

If I have a senior moment and connect a bit of kit (DVD player for example) which runs on the standard house mains with a coax to the preamp on the BMS then the RCD at the consumer instantly trips the BMS transformer. No issue (obviously) if I use optical connect.

Steve

Hmm. Not quite sure this is directly related. This sounds faulty. There should be no issue mixing BPS connected kit with direct mains kit, unless something is faulty. I presume the coax you refer to is standard RCA interconnects. It's interesting to note that Airlink offer as an option an RCD for the output of the device. Clearly they feel such an option serves a useful purpose.

That is almost certainly not normal - and if you have described it properly (or I have understood it properly) I think I would want to get that checked out by a competent electrician. It may relate to the item being installed as an "isolating" transformer, where the ground connection "floats". Your tripping connection is making a connection between the floating ground and true earth. But even so, that should only cause a trip if something is faulty. Best to get it checked.

[Oldpinkman]

The bottom of page 5 on this link http://www.hse.gov.uk/pubns/indg354.pdf

will give you an indication of the potential hazards of mixing isolating transformers and true earths.

[Ali Tait]

Agreed, there would appear to be a fault somewhere.

[worrasf]

In my case I suspect it's the wiring in the rest of the house which needs a re-wire. When I moved in we still had 2-core black and red cloth covered cables running in steel "squirrel proof" pipe in the loft :eek:

[CageyH]

Pinkie,
You don't need to worry about balanced mains if you move to France.
We don't have ring mains here to worry about, and no fuses in our plugs. :ner:

[Gordon Steadman]

Pinkie,
You don't need to worry about balanced mains if you move to France.
We don't have ring mains here to worry about, and no fuses in our plugs. :ner:
Indeed. I also have another ace up my sleeve.

I keep a tame electrician in the house. She is also a good cook (although not as good as me of course), I rather like her in several other ways and she doesn't mind doing the washing and cleaning whilst I'm swanning around pretending to do stuff in the workshop.

Seriously, Ronnie is someone who studies. She won't do anything until she is 100% sure of what she is doing - and still she married me:eek: - she has swallowed the French electrical dictionary. I sometimes have to act as a strong pair of hands but she does all the brain stuff.

I sleep easy and have never had shaky hands when plugging something into the mains.

The hi-fi sounds fab.

[Oldpinkman]

Pinkie,
You don't need to worry about balanced mains if you move to France.
We don't have ring mains here to worry about, and no fuses in our plugs. :ner:

Ring mains are hardly relevant to the BMU issue. Your radial circuits probably still have RCD's. And your appliance may have fuses internally. And a switch to turn it off which probably isn't dual pole. I am intrigued - my original comments were merely to draw attention to these differences and not in any way to suggest the devices were dangerous per se nor inappropriate to use domestically. I was looking at buying one. But the more you look at their relationship with other devices -the more you realise how they "change them". A class 1 or class 2 device expects only to be plugged into a supply with one live connection only. If a device considers it appropriate to have a fuse on the live supply for its CE approval statement, then does it need to be modified if there are 2 live supplies which it is being connected to?

Anyway - right now I am in the UK and we do have fuses in our plugs. It may well be that it is "extra fussy" to have such fuses- but I wouldn't want to go round suggesting anyone replace a cartridge fuse in a plug with a bit of sawn-off 6 inch nail. And using a standard 3 pin UK plug with balanced power is not dissimilar to doing that. edit (on one of the 2 connections carrying a voltage)

[Oldpinkman]

In my case I suspect it's the wiring in the rest of the house which needs a re-wire. When I moved in we still had 2-core black and red cloth covered cables running in steel "squirrel proof" pipe in the loft :eek:

I don't want to start trying to diagnose on the forum - but its probably NOT the rest of the house. The only thing that trips an RCD is an imbalance between the current in the 2 cables physically connected to it. That will usually (always?) be because of a connection between one of them and earth. Physically. By changing the circuit you change the current flowing in one part of it. For example, if you create a path to earth on the neutral wire (not a dead short - but a path with a resistance) , some of the current flowing round the circuit from the live wire, will travel down the new path instead of travelling down the neutral wire which is connected to the RCD, so there will be a different current on the neutral wire in the RCD from the live wire, and if that difference exceeds 30ma (in most domestic devices) it will trip.

This connection to earth only works on a main supply which is in turn grounded to earth - like the neutral supply on our mains is bonded to earth. This means a connection from live to earth can complete a circuit with neutral via that earth route because earth and neutral are bonded. On an isolated supply, like the secondary of an isolation transformer, there is no such bond between neutral and earth, and so a connection from live to earth can't make a circuit since earth isn't bonded to neutral.

So it appears that your BPS on its input supply- the bit connected to the RCD - has a leak which is bigger than 30ma to the ground on that transformer, which is NOT currently connected to earth, since it has been wired as an isolation transformer. Connecting that ground to earth, via the outer connection of an RCA interconnect between the isolated circuit and the mains circuit , which your DVD player is connected to, which is connected to true earth, provides the path to earth which trips the RCD. That would be a possibility, although it means the floating ground must in some way be connected to one side of the primary of the BPS. Not necessarily the answer, but possible.

But NOT likely to be a fault on the rest of the house. If in doubt - get it checked.

[worrasf]

But NOT likely to be a fault on the rest of the house.

I was attempting (failing) to inject a bit of lightheartedness into this thread with my "squirrel proof pipe" reference :eyebrows:

Anyway, what if I told you in the twin and earth cable that goes to my outside "Narnia lamp stand" there is current flowing in the earth wire :stalks: (Well there was until I disconnected it) - From memory about 20v when I put a DVM on it. Only came to light (no pun intended) because despite me switching the light off at it's one and only wall switch the builder tripped the RCD when he drilled through the cable :doh:

Anyway - enough about my electrics

[DSJR]

As an aside, aren't amplifier supplies typically some form of 'balanced' supply to their circuit boards? You have AC going in which is smoothed and rectified, but the transformer secondaries are usually wired for a plus voltage, a minus voltage and a central zero point I understand (cautiously) which can be earthed or floating (I think). I don't know many amps with transformer-secondary failures, although I'm sure it happens occasionally.

Pinky, just stick to accounting. As it's your main competence, you'll have far less of a problem as you know what you're doing here. Me? I've just made a little bench power supply to test old boards with. +/-20V and floating '0' from a small 18VA transformer and for my peace of mind, mounted in a 'Hammond' ABS 'project' box just in case I didn't do it right or the old caps I used were sub standard (they're fine and it worked first time)...

[Sovereign]

Well - a most enjoyable trip to James (Sovereign) nuclear bunker. No BPS testing carried out, partly cos we were busy listening to music and chatting, and mostly because I don't think we had a common connector between the pair of us, including mains plugs. And I didn't fancy trying to wire up my dodgy angle-poise with the firemans hose cables James uses.

So any youtube videos of a BPS isolating the RCD's on the primary will have to wait till I get a unit with conventional mains sockets on. Or an adaptor. And, by preference, if I carry out the test here, the consumer unit converted to RCBO's, because however much I try to isolate using a portable RCD plug its a 50:50 call whether that or the house main RCD blows first, and its a real pain having to reset the whole house every time. May have to treat myself to a PAT test isolator - or borrow Scotties.

Meantime - I felt very old. James had warned me he didn't have vinyl - but I thought we could play CD's (we did by ripping them to the Macbook first). A very enjoyable evenings listening - very different to the presentation I am used to on my system. I think James when he comes round may find my system "ethereal" to the point of weedy. And we will face the lack of common connector challenge (my Dacapo only has toslink, BNC and balanced sockets - James only uses USB) :doh:

Also very jealous - James has a 24/7 listening room, where I have to operate a 9PM curfew out of consideration for the neighbours.

Happily, whilst we appeared not to have a compatible component to swap in sight, we had a good deal more in common when it came to music, so a very enjoyable and informative listening session instead.

And I got to see my first NVA amplifier in the flesh, as well as an LDR passive and a BPS.

Thanks James - my gaff next time

:cool:
Yes it was great to meet up, great to be introduced to some new music, namely David Midgen, an supremely well recorded album, probably the best recording I've heard to date, and local to Kent as well!
Great to talk about hifi that was before my time, I didn't know you were involved in hifi production at all, just thought you were the end consumer. Would have loved to try your old style DeCappo DAC, particularly compared to my DDDAC which I really rate, maybe I can take it over to your place. What I think is the stand out piece of kit to my hifi is my Power Amp, which I would love to bring over to you to, and see how it handles your statics.
My BPS isn't moblie as it stands as it uses Neutrik PowerCons instead of IEC connectors and the BPS is hardwired into the dedicated consumer unit. I can always fit normal sockets and plugs to it to enable you to use it in your system, whatever it takes to show you the benifits of balanced power:)

Let me know when your next free.

[Oldpinkman]

As an aside, aren't amplifier supplies typically some form of 'balanced' supply to their circuit boards? You have AC going in which is smoothed and rectified, but the transformer secondaries are usually wired for a plus voltage, a minus voltage and a central zero point I understand (cautiously) which can be earthed or floating (I think). I don't know many amps with transformer-secondary failures, although I'm sure it happens occasionally.

Pinky, just stick to accounting. As it's your main competence, you'll have far less of a problem as you know what you're doing here. Me? I've just made a little bench power supply to test old boards with. +/-20V and floating '0' from a small 18VA transformer and for my peace of mind, mounted in a 'Hammond' ABS 'project' box just in case I didn't do it right or the old caps I used were sub standard (they're fine and it worked first time)...
Dave. You are quite right. Amplifier designs often have "balanced mains" before rectification. The pip would be an example, at +18v 0v - 18v. Obviously 18v is not a lethal voltage in the way 120v might be. But even that is not the point. Nobody plugs a hedge trimmers 3 pin plug into a pip and thinks they've got good ole reglar "out of the wall" mains. The pip transformer is protected by a 1/2 amp resistor. The danger is not in the fact that the household rcd doesn't protect a nad 3020. You can use a nad 3020 in a house with no rcd protection. The danger lies in insisting the nad 3020 is protected by an rcd when it isn't.

(and my pip shorts - 18v AC to 0v true earth via a bulb and 100 ohm series resistor without tripping the house rcd's in the same way a similar short on a device plugged into a bps wouldn't trip a house rcd. Again the issue is not a failure of the bps - it's a failure on a device plugged into it)
And regarding accountancy - you are quite right. Like others commenting on this safety related matter I have no formal qualifications and might have had a flawed understanding. So, because I was concerned about authoritative statements being made which conflicted with what I thought I understood, I asked a thoroughly qualified expert not just to confirm my understanding, but also to specifically comment on the statements others were making which I felt were wrong. I have been sharing his expertise. Not relying on my own lack of knowledge.

[Oldpinkman]

Dave

Re-reading my reply in the morning, I share Mr Kipling's astonishment that this thread has run for so long. The original point was a really simple one. "Be aware of how using a BPS changes some electrical safety aspects for things you plug into it"

To emphasise the point - its NOT "What's in the box". The issue has nothing to do with the safety of the device itself. Whether we are talking about a BPS or a HiFi amplifier, I take it as read that the device is properly made and designed and complies with appropriate safety criteria, relevant EU standards, CE requirements etc. It's not what happens inside. It's NOT "What's in the box?":doh:

The issue is how you use the box, and whether you understand it. The question is whether one of the sockets on the box can be used the same as any mains socket. Or whether in truth it is not the same as any mains socket.:eek:

Remember - there is no requirement to use RCD's. Something is not inherently dangerous because there are no RCD's in place. But RCD's add a layer of safety - and if you have chosen that layer of safety you need to be aware of whether it is protecting you or not.

So - lets do a slightly contrived example just to really make the point about RCD's. I am on my summer holiday for 5 weeks in August again, and my 82 year old parents are house-sitting for me, to look after the dogs while we are away. It is drizzling a light rain outside, but warm enough to wear shorts and bare feet (my father does, all summer). He has decided to tidy up in the garden a bit for me, with time on his hands, and trim the overgrown hedge on the boundary with next door. I don't let him use my Stihl petrol brushcutter with hedge trimmer attachment, but he's allowed to use the lightweight electric version. He taps on the lounge window, passes my Mum the plug and asks her to plug it in. Being a senile old goat, he slices through the cable whilst trimming the hedge - and everything is wet with this fine drizzle.

Scenario 1. My 82 year old Mum, with macular degeneration dimming her sight, 2 arthritic knees, a fused back, and a morphine patch, says "I won't plug it in the spare socket on the BPS under the window, I'll climb under the low shelves to the socket in the back of the alcove, unplug the BPS and plug the hedge trimmer straight into the wall. Result - a tiny current flows (30ma) for a fraction of a second(50ms), and the RCD on the main household consumer unit trips, and cuts the power. My Dad is left saying "Hell Pat, what is Richard going to say when he gets back and finds I've sliced the cable on his hedge trimmer? He'l call me an "old fool" again" :)

Scenario 2 - same mother, same ailments thinks "Handy - I'll just plug the hedge trimmer into this nice 4-way box with an unused socket that Richard uses for his HiFi". And does so. A much larger current flows, not enough to blow the fuse in the plug and certainly not the MCB's on the consumer unit, but a couple of amps, and my father is thrown back with a lethal shock, and Mum is left organising a funeral, while I have to cut my holiday short to attend it. :(

Does that make it any clearer Dave? Its a small point, but a simple one, and in the context of Mains safety devices like RCD's, I believe, a VERY IMPORTANT one. So how does it cause such controversy? :scratch:

[Ali Tait]

No controversy here.

[Oldpinkman]

As an aside, aren't amplifier supplies typically some form of 'balanced' supply to their circuit boards? You have AC going in which is smoothed and rectified, but the transformer secondaries are usually wired for a plus voltage, a minus voltage and a central zero point I understand (cautiously) which can be earthed or floating (I think). I don't know many amps with transformer-secondary failures, although I'm sure it happens occasionally.

Since we're thread drifting Dave, if a device has a centre-tapped transformer to supply a positive and negative rail in the way you describe, and if that amounts to a balanced AC , then wouldn't plugging that amplifier into another BPS be "like putting a plaster on a plaster". If a BPS in the amplifier cleans the mains, what's the point in cleaning the mains fed into it?

(I should note, that I am not saying a BPS does clean the mains - just wondering why, if it did, you would want to do it twice)

I think if I owned an amplifier from a manufacturer who used such a power supply in the amplifier, and I bought a BPS to plug it into, and then found out it was "like putting a plaster on a plaster" I personally would feel I had been conned. But then I'm sensitive like that :o

[Oldpinkman]

Back on topic a couple of recent events mean I remain concerned this issue is poorly understood. It isn't helped when people make defensive false statements confusing a concern with safety related issues with other imagined agendas. I have been corresponding with Macca privately, and his questions have in essence been "can you explain the real practical dangers"? I listed a few for him, but the 2 most recent incidents are probably a good summary.

Macca had previously posted that those with legitimate safety concerns should report them to the authorities, so I have followed that advice. But I still don't like the idea that what is, in essence a simple concept, seems so badly misunderstood. My example of my parents house-sitting and cutting the hedge was one example of a real practical danger. If that seems contrived, it is worth bearing in mind why one would ever install an RCD at all, or why one would ever use an inline fuse. They are to protect against unusual events, not a day to day constant danger. And whilst deaths from domestic electrocutions occur, they are mercifully rare. Deaths from fires caused by electrical faults are far more prevalent.

I will break this into 3 posts, since I am usually accused of being too long. To recap, the device (a Balanced Power Supply - BPS) is not necessarily dangerous itself. What is dangerous is to fail to understand how it changes the electrical supply we use, and common safety precautions which are changed by the use of a BPS. Why it is not, and cannot be used like "any mains socket". Again, false statements about these matters are unhelpful and dangerous, possibly criminally so. Ideally a manufacturer should issue appropriate safety warnings, so that the device is properly understood, and any risks can be minimised. Some manufacturers of BPS do this, and / or fit appropriate safety protection to their products. So, there are basically 2 issues

1) RCD protection. If you have RCD's on your main consumer unit (and not everybody does) then a fault on a device which is plugged into a BPS, including an earthed human touching a live wire, will not trip the house RCD, which will not offer any protection. Note this has to be a fault of the type RCD's are designed to protect (like my dad cutting the wire). If the fault is a dead short (or very low resistance short) a fuse or MCB may protect. If a device has a fault such as a leak to earth, then it will trip the RCD if it is plugged into "any normal mains socket" but it will not trip the RCD if it is plugged into a BPS.

2) A socket on a BPS has 2 live connections instead of just one. If you want to switch off power, either with a control switch (on/off switch) or a fuse or other circuit breaker, then the switch or fuse(s) have to be fitted to 2 wires and not one. Most equipment which is manufactured for use with "normal" mains only switches and fuses the live wire, because it doesn't expect there to be any power on the "neutral" wire.

Not that hard to understand really.

[Oldpinkman]

First situation. I received correspondence from someone who knew I had an interest and had been researching. They had built a 2KVA BPS and were testing it (I know not why) with a 3KVA fan heater plugged in. They left if for an hour whilst they had lunch, and came back to a burning smell. The BPS transformer was 115 degrees celsius. And they said (and I quote) "the household RCD knew nothing about it".

This illustrates 2 points - and 2 points which appear widely misunderstood.

The first, is a misunderstanding about the RCD issue and how RCD's work. There was nothing wrong with the fan heater - which was simply attempting to draw too much current. The overloaded device in this situation was the BPS itself, not something plugged into it. The RCD didn't protect because its not designed to. An RCD only detects a current difference between live and neutral. In this situation, there was no difference in the current - it was just that the overall current was too high. This wasn't a case of a BPS causing an RCD to be defeated - there was no fault of the type RCD's detect. A different safety issue was at stake

So the second thing it highlights is how easily faulty or misused electrical appliances can start a fire. Mercifully that didn't occur on this occasion - it got too hot, but not combustibly too hot. The safety item missing was a 10 amp cartridge fuse in the supply to the BPS which would have blown with the 12.5 amps the fan heater was trying to draw. Note - one fuse in the live supply to the BPS would do the job and cut all power to the fan heater, since only the live wire between the wall and the BPS carries a current once that live supply is cut. (Obviously current flows down the neutral wire when a component completes a circuit, but no power is on the neutral line unless there is power on the live line)

Now in the context of this fire risk, if the BPS was operating within capacity and the excess current was on the device plugged into it, that device would have an appropriate fuse in its plug as protection. But now that fuse will cut power to the live line - and leave power flowing down the neutral line. One fuse doesn't cut all the power to the device - it just cuts the power from the brown wire not the blue one. If the fault causing the excess current were a resistive leak to earth, then it could continue in these circumstances. That is why Ali fitted MCBO's to both output rails. (and even they only limit the current generically - not on a product specific way that a cartridge fuse in the plug does. Ali's RCBO's limit current to maybe 10 amps. My Pip has an inline fuse which blows at 250ma)

The risks may not be every day, but it is important to properly understand them, and not make factually inaccurate statements about them.

[Oldpinkman]

2nd situation

I had my chimney swept for the first time in about 5 years (we only have half a dozen or so fires a year - all with seasoned apple wood). The new chimney sweep had a new (to me) device. Effectively 4 strimmer wires on the end of the rods, which were rotated at high speed by a conventional (B&Q) drill. I have to say I would have invested in a cordless, but he had a standard plastic bodied B&Q mains drill.

Cracked plastic bodied - he had obviously dropped it or run it over at least once. This drill was held in one hand, while the other hand usually guided the rods, but occasionally rested on the earthed cast iron stove he was sweeping. Whilst I was out making him a cup of tea, he plugged his drill into the nearest available socket - the 6-way for my HiFi. Could easily have been a 4 way BPS. Now, the drill wasn't dangerously faulty on this occasion, but this individual clearly economised a bit, and one day it might be.

If that drill had been faulty in a way which caused the live wire to be in contact with the man, whilst he was touching the fire, then

if the drill had been plugged direct into the wall - the RCD would have tripped in milliseconds before 30ma of current had flown

if the drill had been plugged into a BPS - the RCD would NOT trip and the man would have suffered a more severe, possibly lethal, electrocution.

This was a real situation. OK, the drill wasn't that faulty this time. But the hapless use of a BPS as "just any ordinary mains socket" was very real. And it illustrates the type of situation RCD's are designed to protect, and how the use / existence of a BPS creates a potential hazard by removing the protection of the household RCD from the appliance plugged into it.

Hopefully that is now understood. There is no requirement to have RCD's in a house. In a house without RCD's the chimney sweep would have suffered the same risk as he did in my house using a BPS - a greater risk actually since the voltage in question would be 230v instead of 115v. You don't have to have RCD's, but if you do have them, it is important to know when they are protecting you, and when they are not.

Maybe our chimney sweep should carry one of these

http://i1315.photobucket.com/albums/t582/oldpinkman/RCD_zpse3315ecb.jpg (http://s1315.photobucket.com/user/oldpinkman/media/RCD_zpse3315ecb.jpg.html)

Or maybe he should get a new drill :doh:

[Ali Tait]

That is indeed one of the reasons I fitted a two pole device on the secondary. However, though I have designed mine to be portable (two man lift though!) , in use it only powers the system and the telly. There is nothing nearby that isn't plugged into the BPS, another source of potential danger.

[Ali Tait]

Also, it is one reason that special sockets are often used for balanced power situations, so that nothing else can be plugged in.

[Oldpinkman]

That is indeed one of the reasons I fitted a two pole device on the secondary. However, though I have designed mine to be portable (two man lift though!) , in use it only powers the system and the telly. There is nothing nearby that isn't plugged into the BPS, another source of potential danger.

Go on. I fear I'm opening a can of worms, but this one isn't immediately apparent to me. Why would it matter if something is plugged into a normal mains socket and is physically close to the BPS? :scratch:

[Ali Tait]

Because under certain fault conditions, assuming the equipment plugged in is not double insulated, there could be current flow if both pieces of equipment were touched at the same time.

[Ali Tait]

By this I mean that if two separate pieces of equipment were close to each other, one run balanced, the other not.

[Marco]

I had my chimney swept for the first time in about 5 years (we only have half a dozen or so fires a year - all with seasoned apple wood).

Jeez - are you another one of the ‘multiple jumper brigade’, along with Gordon [ask him if you don’t know what I’m referring to here]? ;)

We’ve got our fire lit all day, every day now - and that’ll be the status quo until the end of winter! As a result, our chimney sweep comes out two or three times a year. No BMUs here though, nor are there ever likely to be, as significant and rather obvious safety issues aside, I don’t rate them.

Marco.

[Oldpinkman]

Because under certain fault conditions, assuming the equipment plugged in is not double insulated, there could be current flow if both pieces of equipment were touched at the same time.

No - you've still got me. The implication is that the "normal" socket is earthed, and the BMU has a floating ground. I have assumed that BPS sold for domestic use have the secondary ground connected to true earth and not floating, since otherwise there would be no path to true earth for an appliance plugged in and that would breach class 1 regs. If a BPS has a floating ground, then, in addition to that question mark about its affect on class 1 appliance regulation compliance, it would be a true isolation transformer, and there is no electrocution risk from a contact with earth, since no circuit is completed.

(This is the can of worms I didn't want to open - because I think a lot of distracting fog is created discussing the differences between class 1 and class 2 and the regulations relating to them, and ignoring the simple electricity point of how current flows in a circuit, and how a transformer and RCD work)

Otherwise, I don't understand the current flow from one class 1 chassis to another. Surely any BPS sold for domestic use is NOT isolating and has secondary ground connected to true earth??? :scratch:

[Oldpinkman]

Jeez - are you another one of the ‘multiple jumper brigade’, along with Gordon [ask him if you don’t know what I’m referring to here]? ;)

We’ve got our fire lit all day, every day now - and that’ll be the status quo until the end of winter! As a result, our chimney sweep comes out two or three times a year. No BMUs here though, nor are there ever likely to be, as significant and rather obvious safety issues aside, I don’t rate them.

Marco.

No - I just installed oil fired central heating. The fire is decorative really - we have to turn the radiators down to enjoy a good toasty time around it. I love a good real fire (even in a stove) but not to rely on for heat. Until the divorce we has a big Coalbrookdale Severn with a back boiler squeezed in where the current we stove is, and had to light a fire every day to get the radiators warm. The oil boiler's a lot easier :)

[Gordon Steadman]

Jeez - are you another one of the ‘multiple jumper brigade’, along with Gordon [ask him if you don’t know what I’m referring to here]? ;)

We’ve got our fire lit all day, every day now - and that’ll be the status quo until the end of winter! As a result, our chimney sweep comes out two or three times a year. No BMUs here though, nor are there ever likely to be, as significant and rather obvious safety issues aside, I don’t rate them.

Marco.

:)

I sweep our chimneys every year and nothing ever comes down. Both woodburners are so efficient, virtually nothing ends up as waste. I don't like the rooms to be too hot. If I can manage in a T shirt, its too hot for me. (Our 1 metre thick walls keeps it all nice and cool in the summer too)

We have both fires on tick over all day and it keeps the place very comfortable actually doing stuff rather than just sitting around doing bugger all.:eyebrows:

I don't know anything about BMUs and not much more about the alternative spelling.

[Gordon Steadman]

No - I just installed oil fired central heating. The fire is decorative really - we have to turn the radiators down to enjoy a good toasty time around it. I love a good real fire (even in a stove) but not to rely on for heat. Until the divorce we has a big Coalbrookdale Severn with a back boiler squeezed in where the current we stove is, and had to light a fire every day to get the radiators warm. The oil boiler's a lot easier :)
Hate central heating. Dry air, sore throats, runny noses. I'll stick to woodburners.

[Oldpinkman]

. No BMUs here though, nor are there ever likely to be, as significant and rather obvious safety issues aside, I don’t rate them.

Marco.

I'm reserving judgement. Sovereign is very keen for me to try his - although it will have to run off a multiway adaptor connected to it - which will doubtless be the reason given if there are no benefits. As you know, I am not a big mains fusser, and I think my earthing arrangements are fit for purpose - but I don't mind trying.

I have another mains experiment planned for this weekend to do with my Raspberry Pi project on another forum - although I am rather more confident that particular experiment will be a bust. (removing "noise making" home plugs from the system). We'll see... :cool:

[Oldpinkman]

:)


and not much more about the alternative spelling.

Oh bother - I got suckered in there :doh:

[struth]

alternative spelling being :lol:bums

[Oldpinkman]

I'm reserving judgement. Sovereign is very keen for me to try his - although it will have to run off a multiway adaptor connected to it - which will doubtless be the reason given if there are no benefits. As you know, I am not a big mains fusser, and I think my earthing arrangements are fit for purpose - but I don't mind trying.

I have another mains experiment planned for this weekend to do with my Raspberry Pi project on another forum - although I am rather more confident that particular experiment will be a bust. (removing "noise making" home plugs from the system). We'll see... :cool:

On the subject of mains experiments it isn't hard for anybody (confident with mains) with a BPS (of whatever flavour) to prove the point about RCD's not working. Take a Homebase table lamp for £5, wire neutral to earth, plug it into your "normal mains" and it will blow the RCD (assuming you have one) - plug it into a BPS and it will glow less brightly than normal and not trip the RCD. Sadly I couldn't persuade Macca to try it although I offered to lend him an RCD :(

Clearly, if you already understand how electricity works the test is superfluous, and the result obvious.

[Macca]

. Sadly I couldn't persuade Macca to try it although I offered to lend him an RCD :(


I did try really, really hard to care but ultimately I fell short ....;)

[Joe]

I will break this into 3 posts, since I am usually accused of being too long.

Surely not!

[Sovereign]

Interesting findings Richard, and I hear some of your safety concerns, I have made a silly mistake myself. But I would have to come back to my post ages ago that these devices need to be used with knowledge and wisdom. I would say that your wood burning stove is many many many times more dangerous than a balanced toroidial. But every one knows not to put a newspaper on top of it, not warn children who may touch it and all the other precausions that one would take when living with a fire in a house. None of that is said to negate your thoughts on safety concerns though. But in the context of my BPS and HIFI I dont have a chimney sweep likely to attend, water tanks above, little children prying or anything else of the like. Even if I had my HIFI in my lounge no one would be pluging anything into my MF-BPS as I use Neutrik Power connectors as I dislike fuses.
If a BPS is sold as a product perhaps Ali's approach is the only one to take, because who knows how the product is to be used. Its because of idiots and stupid mistakes that safety laws are introduced and become the norm. But when I'm that idiot I'm greatful of the safety measures that have been put in place in everyday life.
The difference they make to the sound of my HIFI? My HIFI sounds good without it, with the MF-BPS in place it sounds bloody fantastic. So much low down bass, control, detail and tonal accuracy. Wouldn't have it any other way.

[Ali Tait]

No - you've still got me. The implication is that the "normal" socket is earthed, and the BMU has a floating ground. I have assumed that BPS sold for domestic use have the secondary ground connected to true earth and not floating, since otherwise there would be no path to true earth for an appliance plugged in and that would breach class 1 regs. If a BPS has a floating ground, then, in addition to that question mark about its affect on class 1 appliance regulation compliance, it would be a true isolation transformer, and there is no electrocution risk from a contact with earth, since no circuit is completed.

(This is the can of worms I didn't want to open - because I think a lot of distracting fog is created discussing the differences between class 1 and class 2 and the regulations relating to them, and ignoring the simple electricity point of how current flows in a circuit, and how a transformer and RCD work)

Otherwise, I don't understand the current flow from one class 1 chassis to another. Surely any BPS sold for domestic use is NOT isolating and has secondary ground connected to true earth??? :scratch:

Do they? Dunno, you'd think so.

The reason mine is built the way it was is so that it is safe to use in any situation.

[Joe]

Richard's posts increasingly resemble the intro to a Casualty episode, where far-fetched scenarios set the scene for a series of nasty accidents.

How 'dangerous' are these things to use compared to, say, yer average valve amp? Could a qualified electrician comment?

[Oldpinkman]

I did try really, really hard to care but ultimately I fell short ....;)

That's a shame. If more people cared the world would be a better place :)

And I feel a forum should care whether the truth is promoted or suppressed. And should care about electrical safety.

In his BPS thread Ali stated he fitted RCD's (RCBO's actually) on the output of his BPS. Others have stated, wholly untruthfully, that these serve no purpose. That they are "a plaster on a plaster". And that the RCD on the input will provide all the protection needed.

So the question is a simple one, whether just on a forum, or in court defending libel or a Trading Standards prosecution. Which statement is true? Does an RCD on the input of a BPS provide the same protection as an RCD on the output? Ali and I have tried to explain, but it seems it is too difficult for some people to understand. The obvious response is to demonstrate with an appropriate methodology. This is the method ,

1) obtain a device to test an RCD's function. I have suggested a table lamp. I will explain why in another post. For now we just need to observe that it works
2) Plug a portable RCD into a mains supply which is not itself protected by an RCD (preferably**)
3) Plug the lamp into the RCD and observe that the RCD trips. Unplug. Reset the RCD
4) Plug the BPS into the mains, and plug the RCD into the OUTPUT of the BPS. Plug the lamp into the RCD and observe it trips. An RCD on the OUTPUT of a BPS protects from the "fault"
5) Unplug all, reset the RCD, plug the RCD into the mains, plug the BPS into the RCD, plug the lamp into the BPS and observe that the RCD DOES NOT TRIP. The lamp will glow, less brightly than normal since it is powered by 115v instead of 230v. An RCD on the INPUT of a BPS does not trip when there is a fault on the output

This simple test proves what Ali and I have been saying, and why Ali fitted MCBO's to the output of his BPS. There is no need to understand HOW (but I will explain in another post). It just works, and is obvious. For anyone to state that this simple truth is UNTRUE displays that persons shocking ignorance of basic electricity. (pun intended). If you already have an electricity supply without an RCD and an available BPS - the test equipment costs £8 for a portable RCD and £5 for a lamp from homebase maximum. I offered to lend mine. Maybe the forum should sponsor this test in the cause of establishing the truth of Ali's and my safety advice.

** It is better if the "test environment" is not itself protected by an RCD, like Macca's house, or Sovereigns HiFi Room. The RCD's tend to compete for who can trip first. In my house its often the main RCD on the consumer board which goes before the portable RCD which is a bloody nightmare because it turns off power to everything, and SWMBO objects. If the test has to be carried out on a circuit protected by an RCD, such as in court, then an engineer carrying it out would use a transformer to isolate the test environment from the building circuit, and all test would be plugged into the transformer outputs. Thats because transformers are used to physically isolate one circuit from another, so the court RCD's won't be tripped by anything on the output of the transformer. If I have to do much more testing here, I am going to have to build myself an isolation transformer - or change the consumer board to RCBO's. (That is get Graham, my electrician to change the consumer board!!);)

[Gazjam]

If it helps the cause Richard, my BPS installation was signed off by a NICEIC certified electrician.

The only potential "gotcha" was the fact that I had hard wired my BPS into the wall thereby removing a switchable socket and being unable to switch power off at the wall.
The fact though that my BPS (thanks to Ali's suggestion) had 2 pole switchable RCBO's on both primary and secondary power legs covered that happy to say.
Effectively...the switchable RCBO's became the "switched socket" that cuts off power at the source.

All good, all signed off and makes a significant improvement to the hifi.



How 'dangerous' are these things to use compared to, say, yer average valve amp? Could a qualified electrician comment?
Joe raises a good point here I think?
Danger is everywhere and you just make sure you put the appropriate safeguards in place...really that's all you can do unless you want to live in a cave!

We all need to make an informed choice on what we are prepared to do...
For me, the fact that BPS systems are used in music studio's around the world points to their "acceptable factor of safety."
Also Ali Tait knows what he's doing with electrical safety and advised me every step of the way.
Despite being all out for best sound quality like the rest of us, he errs on the side of safety - and that was good enough for me.

As I say everythings an informed choice, but ask yourself a few questions though...

Does my old Microwave leak?
Should I really have so many extension sockets hooked together?
Is it a bad idea to drink so much?
I really SHOULD replace the old central heating boiler...but its so expensive to get a new one in?

You choose to live with what you do, know what I mean?

[Sovereign]

Richard the points you are stressing in my view are going a wee bit over the top.
A totally unprotected BPS like mine is safe if used correctly, not sure if I would advise for it to be sold like this though. So is a fast car, wood burning stove etc. A man can accidentally kill himself with a pencil if he is not careful.
When I'm back from Capetown in January come round with the various tests you want to run and you can run them all and take notes of your findings. Conveniently, as you know, my hifi has its own consumer unit three feet away from my BPS, the consumer unit has both a RCD and a MCB so you don't have far to travel to re set them...........should they trip out.

[Oldpinkman]

James

The issue isn't an absolute declaration of safety. We can all make choices. Some houses don't have an RCD at all, so none of the sockets in the house are protected by an RCD. That is an acceptable choice.

So it is legitimate to choose to fit RCD's or MCBO's on a BPS, or not to.

However, it is not true to say that fitting an RCD on the output of a BPS is pointless, and does nothing. It is not true to say that an RCD on the input of a BPS will protect in the same way that an RCD on the output will. Never mind issues of safety - those statements just demonstrate ignorance of how electricity works.

So - a dispute had developed, not so much about what one MUST do to be safe, but about how safety devices like RCD's work, and therefore what one should do IF one wanted the protection of an RCD

The answer is IF you want the protection of an RCD and you use a BPS the RCD MUST be fitted to the output. That simple test I outlined demonstrates that. We could do it at your place. And the test demonstrates that anyone who says otherwise is mistaken, and demonstrating their ignorance of how electricity works. An RCD on the output of a BPS is not a "plaster on a plaster". It is THE ONLY WAY to get RCD protection for devices plugged into a BPS IF YOU WANT THAT.

Its not prescriptive about what safety measures you must take. It's clearing up dangerous misinformation about HOW to take those safety measures IF you want to take them.

Of course, now that I have raised the matter with trading standards it begs all kinds of issues about what "the rules" for safety say. But that's trading standards problem, not mine. I think as a minimum they will require a product sold commercially to have appropriate, accurate, honest safety warnings. And not to make claims that are untrue. But maybe not.

[Sovereign]

James

The issue isn't an absolute declaration of safety. We can all make choices. Some houses don't have an RCD at all, so none of the sockets in the house are protected by an RCD. That is an acceptable choice.

So it is legitimate to choose to fit RCD's or MCBO's on a BPS, or not to.

However, it is not true to say that fitting an RCD on the output of a BPS is pointless, and does nothing. It is not true to say that an RCD on the input of a BPS will protect in the same way that an RCD on the output will. Never mind issues of safety - those statements just demonstrate ignorance of how electricity works.

So - a dispute had developed, not so much about what one MUST do to be safe, but about how safety devices like RCD's work, and therefore what one should do IF one wanted the protection of an RCD

The answer is IF you want the protection of an RCD and you use a BPS the RCD MUST be fitted to the output. That simple test I outlined demonstrates that. We could do it at your place. And the test demonstrates that anyone who says otherwise is mistaken, and demonstrating their ignorance of how electricity works. An RCD on the output of a BPS is not a "plaster on a plaster". It is THE ONLY WAY to get RCD protection for devices plugged into a BPS IF YOU WANT THAT.

Its not prescriptive about what safety measures you must take. It's clearing up dangerous misinformation about HOW to take those safety measures IF you want to take them.

Of course, now that I have raised the matter with trading standards it begs all kinds of issues about what "the rules" for safety say. But that's trading standards problem, not mine. I think as a minimum they will require a product sold commercially to have appropriate, accurate, honest safety warnings. And not to make claims that are untrue. But maybe not.

Fair enough mate, I guess I was coming from the perspective that all of the above is not what I have said, but I see your point it is what others have said that bothers you so much. The thing is when a BMU is sold, we don't know how it will be used or who will use it, so therefore it should be protected, as a muppet may use a BMU in a Muppetry way and there is no way of protecting that muppet as the BMU stands, no matter what breaker goes before it, it is what protection is after it that counts.

[DSJR]

No - you've still got me. The implication is that the "normal" socket is earthed, and the BMU has a floating ground. I have assumed that BPS sold for domestic use have the secondary ground connected to true earth and not floating, since otherwise there would be no path to true earth for an appliance plugged in and that would breach class 1 regs. If a BPS has a floating ground, then, in addition to that question mark about its affect on class 1 appliance regulation compliance, it would be a true isolation transformer, and there is no electrocution risk from a contact with earth, since no circuit is completed.

(This is the can of worms I didn't want to open - because I think a lot of distracting fog is created discussing the differences between class 1 and class 2 and the regulations relating to them, and ignoring the simple electricity point of how current flows in a circuit, and how a transformer and RCD work)

Otherwise, I don't understand the current flow from one class 1 chassis to another. Surely any BPS sold for domestic use is NOT isolating and has secondary ground connected to true earth??? :scratch:


Richard, I use forty year old US made amps and these have bare uninsulated mains wires around 1/4" from exposed pressed soft metal parts in the case! The tension in the screwing up of the bent case providing minimal safety in the power amps (the preamp has an insulating thick card to help).

You don't understand and neither do I. Why not leave it there and stop bothering yourself about it. I couldn't afford one anyway..

[Oldpinkman]

And finally for tonight - why use a lamp to test an RCD?

(Assuming you want to test an RCD.)

An RCD is a device which detects an imbalance in the current flowing through its 2 connections (live and neutral). If the current in one connection is 30ma different from the other, then the device trips and cuts the power. This difference is usually caused by a leak to earth. That is their raison d'etre. They are often known as "earth leakage devices". They were invented so that if a current path to earth were made by a human inadvertantly touching a live cable, the device would save his life. They stop the power before enough current has flowed to stop a heart.

So the test that is carried out, to see if they are working, is to connect live to earth. That is what the little test button on them does. If we want to test whether an RCD is working on the input to a BPS, and the output of a BPS in the way my earlier post described, we need to connect live to earth where we want to perform the test.

It would be stupid and dangerous to just do that with a bit of wire. It also misses the point because it would cause a high current to flow and that would blow a fuse (or MCB - miniature circuit breaker, or RCBO - which is an RCD and MCB combined). We don't want to blow the fuse with a big current. We want to see if a small current flowing to earth with trip the RCD

So we need a resistor of the right value, and right power rating. Sorry subjectivists. Time for some sums. I'm going to use slightly unconventional symbols for Ohms law - but not to worry. The law is the same whether we use "I" for current or "A" for current (or as my Dad originally taught it to me, "C" for current). We'll use A for amps. Because that way when we work out how much power is there, we can refer to power in Watts being Volts times Amps

So W=VxA (so a 3Kva transformer, would be able to handle 3000 volt amps, or 3000 watts or 3Kw)

Ohms law - A=V/R Current in amps equals volts divided by resistance (in ohms).

If we just use a bit of wire, the resistance is near zero - lets use 1 ohm to keep the sums easy. So on the input to the BPS where there is 230v between live and earth a current of 230/1= 230A is going to flow - and one would hope that would blow a 13 amp fuse! On the output, the current is smaller because the volts are 115, so the current would be a mere 115amps. Still enough to blow a 13 amp fuse.

We don't have to get down to 30ma (30/1000 of an amp). Somewhere in the region of 500ma to 1 amp is fine. So a resistor of about 500 ohms should do the job. Now, we can't just pull a resistor from our electronics box - the nearest value would be 470 ohms - because the resistors in my box are 1/2 watt. And if we have a 500 ohm resistor, the current flowing at 230v is (about) half an amp, and so the power in watts is 230x0.5 = 115W.

However, a 60w incandescent light bulb is (about) a 500 ohm resistor with a suitable power rating (you can plug a light bulb into the mains).

So if we wire the blue wire to earth on our lamp, we have made a circuit from brown live to blue earth using a suitable resistor to give us about a half amp of current - SAFELY! That's why I picked a lamp as my RCD tester - to make a safe connection from live to earth with a resistor of a suitable value.

Simples! ;)

[BilliumB]

Richard, I'm a bit muddled - won't connecting the 'negative' leg of the BMU to Earth in your plug act as a direct short on one side of your balanced transformer secondary and hence draw significant current in the primary - and hence trip the safety device (fuse?) on the primary?

If I understand you correctly, I think your circuit design simply has the lamp across 2 taps on the secondary (the '+' and 'centre' taps) and a dead short across the 'centre' tap and the '-' tap.

If you simply connected the lamp between the '+' and the centre tap, then the bulb would run at 115v and be dim. In this case I doubt that the protection on the primary would trip. Perhaps a circuit diagram would make things clearer.

Cheers. Bill

[Oldpinkman]

Bill
I'm using a phone so forgive me for not re-reading carefully. I had in mind a class 2 lamp with just a brown and blue wire. Brown goes to live pin on the plug which will be + on the secondary and blue goes to earth on the plug which is zero, centre on the secondary. That connection is across a 500ish ohm resistor. Does that make sense?

[evir]

if I got asked to certify a domestic system with a BPS installed at a socket, then the BPS would become part of the fixed installation and need to comply up to 2011. the BPS supply circuit would need a suitable RCD and the output of the BPS would need to pass 1/2I 1I and 5I tests with a certified RCD tester; I being the rated RCD trip current. If it failed the tests, then it's not safe and that's that.
If the RCD is on the secondary side of a BPS with a 13A socket output then it would then have to pass the above tests. if the primary RCD tripped first you would need to time delay it. there would be a few other factors to consider as it all need's to be up to standard, never mind the earthing.

I ditched the idea of a tranny myself and haven't came across one as above, so all off the top of my head.
You could advise that if you use it, not suitably protected but with due care, then it's unlikely to kill someone but you wouldn't get no certificate.

[Marco]

Probably best that products such as these are avoided, as there seems to be rather too much of a ‘grey area’, in terms of their apparent safety (or otherwise).

When it comes to electricity, folks, the safest course of action is always to take no chances. No system sound improvements are ever worth putting your life at risk for! :nono:

Marco.

[Sovereign]

No, they are actually perfectly safe if used correctly, as a car is perfectly safe if driven correctly.
This thread is jammed full with way too much long winded bumph that is just clouding the issue. Use balanced power correctly and it will reward you with good sound. Any muppet can put a metal object on a live terminal and get a shock. There is more risk in cleaning your toilet with bleach then there is using unprotected balanced power.
I'm bailing out of this thread as it's going nowhere.

[Joe]

Probably best that products such as these are avoided, as there seems to be rather too much of a ‘grey area’, in terms of their apparent safety (or otherwise).


Valve amps are far more (potentially) dangerous.




When it comes to electricity, folks, the safest course of action is always to take no chances. No system sound improvements are ever worth putting your life at risk for! :nono:

Marco.

The safest course of action is always to consult a qualified electrician rather than an accountant.

[Marco]

Hi James,


No, they are actually perfectly safe if used correctly, as a car is perfectly safe if driven correctly.


Sure, but the point is that unpredictable things can happen, which can turn normally perfectly safe situations into unsafe ones - and that’s certainly the case with driving, so why take the risk with electricity?

In terms of risk assessment, the difference is that most of the time driving is a necessity; owning a BMU isn’t.

Marco.

[Marco]

Valve amps are far more (potentially) dangerous.


Lots of things all around us are potentially dangerous. It’s simply up to us to assess the danger and make a judgment call accordingly. That’s all anyone can do. However, the responsible advice to give, when tampering with the mains supply, is always to err on the side of caution.

Marco.

[Joe]

Lots of things all around us are potentially dangerous. It’s simply up to us to assess the danger and make a judgment call accordingly. That’s all anyone can do. However, the responsible advice to give is always to err on the side of caution.

Marco.

So don't use valve amps. They could easily cause a nasty burn to an inquisitive toddler or befuddled OAP, at best, and death to a clumsy DIYer at worst. As I say, if in doubt, consult a qualified electrician, and treat forum advice with caution.

[Marco]

As I say, if in doubt, consult a qualified electrician, and treat forum advice with caution.

Absolutely - and that (very good) advice equally applies to BMUs and those elsewhere promoting their use :exactly:

Marco.

[Marco]

In terms of the safety (or otherwise) of valve amps, here’s an excellent article, written by Barry, for The Knowledge section of AoS:

http://theartofsound.net/forum/showthread.php?35586-Safety-considerations-to-be-made-when-using-valve-amplifiers&p=602933#post602933

It also puts to bed some of the ludicrous claims about valves generating harmful X-rays :mental: made by those with an obvious commercial agenda, in favour of selling solid-state amplification, by attempting to discredit the use of valves.

Marco.

[Macca]

No, they are actually perfectly safe if used correctly, as a car is perfectly safe if driven correctly.
This thread is jammed full with way too much long winded bumph that is just clouding the issue. Use balanced power correctly and it will reward you with good sound. Any muppet can put a metal object on a live terminal and get a shock. There is more risk in cleaning your toilet with bleach then there is using unprotected balanced power.
I'm bailing out of this thread as it's going nowhere.

Well said James. As Joe says aside from some bizarre 'Casualty' type set of circumstances there is not a danger and such circumstances could equally apply to any mains powered electrical device, the things most people's homes are full of.

[struth]

So don't use valve amps. They could easily cause a nasty burn to an inquisitive toddler or befuddled OAP, at best, and death to a clumsy DIYer at worst. As I say, if in doubt, consult a qualified electrician, and treat forum advice with caution.

I would be inclined to say if you have toddlers the your unprotected valve gear should be safely locked away from little hands just like you lock up medicines cleaning products etc. Use common sense with such things ..Bps should only be used when qualified electrician has signed it off as safe and fit for purpose just as you would when fitting a new gas fire you need a gas man to say it is safe

[Oldpinkman]

Probably best that products such as these are avoided, as there seems to be rather too much of a ‘grey area’, in terms of their apparent safety (or otherwise).

When it comes to electricity, folks, the safest course of action is always to take no chances. No system sound improvements are ever worth putting your life at risk for! :nono:

Marco.

That is of course an opinion you are entitled to, but not one I share. My interest in this subject was discussing the safety aspects which should be considered when using a BMU - and not condemning them as unsafe. I will be interested to try Sovereigns unit, and if it makes any differences to my listening which I think are worthwhile, then I may well get or build one.

I think if I do get one, mine, like Ali's , will have dual RCBO's on the output. They're only a tenner for goodness sake. Not just from the electrocution issue (which is a very remote risk) but more from an insurance perspective in the event there ever were a fire. I note Airlink offer this as an option, and Russ Andrews fit dual mcb's as standard.

What I hoped was that this would promote understanding of the subject, not turn into a factional fight. (I am astonished by how people with apparant expertise, seem not to understand how an rcd works, nor why a transformer will isolate the circuit with the rcd from the circuit with the device one might want to protect). So many people make comments not related to the issues previously discussed in response to them. I am reminded of the exam advice I gave my kids, which I consider to be the fundamental best exam technique of all time. RTFQ - read the fucking question. So many people in an exam talk about something they recognise in a question instead of answering what it actually asked.

The purpose here is to discuss which safety features should be considered, and how they may be relevant, whether in fixed installations or portable devices. Safety issues these days are dominant for most manufacturers. My new Karcher K5 pressure washer takes up the first 3 pages of a slim instruction manual with safety warnings. It's a glorified garden hose for heavens sake, not a lethal weapon. But it is considered responsible to make appropriate safety warnings.

Just because a house doesn't have RCD's doesnt mean it is irreponsibly dangerous to live in it. But because a house chooses to have RCD's isn't stupid, unnecessary or pointless as some have implied. We can make choices.

They will be better choices if they are informed ones. My choices will err on the side of maximum safety. Provided they properly understand the risks (which may only be slight) others are welcome to make different choices.

[Joe]

I would be inclined to say if you have toddlers the your unprotected valve gear should be safely locked away from little hands just like you lock up medicines cleaning products etc. Use common sense with such things ..Bps should only be used when qualified electrician has signed it off as safe and fit for purpose just as you would when fitting a new gas fire you need a gas man to say it is safe

Indeed. I didn't use valve amps myself until my children were well past the toddler stage, and have stopped using them now that I'm a befuddled old person. As always, get advice from people who are qualified to provide it (as an aside, it never ceases to amaze me how many people seek medical advice on audio and other forums. See a doctor FFS!).

[DSJR]

Marco, I have to say and with respect to Anthony TD, that your own valve amp is exceptionally well made and carefully thought out, judging by the pics you've posted in the past. His own current production shields the valves well I believe and you don't have kids and possibly don't let the cats anywhere near it. However, whenever I use my rebuilt Quad II's, I NEVER leave them unattended for more than a very few minutes, as I remember the self-destruction of one of the original KT66's, as well as the firework display my Croft OTL demonstrated when I was entertaining friends one Saturday - and sitting next to the bloody thing at the time as well!!!!!

I've seen the innards of early AI valve amps and can say that the internal construction originally was nowhere near as good as we've been privileged to own. How these things outlasted the guarantee period at the time is beyond me, although good service engineers would have sorted them out long ago as each one failed and as the basic design seems stable, I doubt there were any faults due to design inadequacy (subsequent OTL's Glenn made had regulated supplies fitted as standard I remember, which mine didn't have).

Why am I saying all this? It's because of the constant griping about what seems an essentially non-event kind of scenario I believe. All modern amps have dual rail 'balanced' supplies inside, the mains transformer (usually inside a METAL CASE) effectively doing what a BMU does, by taking the 0-230V mains and converting it to a lower + and - rail (often around 47V at the amp board in many popular-priced designs and far higher in very big amps). I have a little test-bench supply (+ and - 25V or so) with external flying leads terminating in crocodile clips so I can test amp boards of different makes (the first time I ever did serious DIY on power supplies) and if the board I'm testing has a dead short on one leg (faulty transistor which can happen from new occasionally), all that happens in my simple situation is that the LED for that leg either goes out or doesn't come on in the first place on a quick test switch-on-off. No fuses blow, no sparks from caps or transformer, just 'nothing.' Now, I do appreciate that a BMU of any make will be working at +/- 115V and with higher current capacity, but like my little supply, there would or should be an earthing plane connecting the 0V tap to the mains earth (hope I'm right here). Should a supply leg after the BMU suffer a short, surely the mains supply BEFORE the transformer would purely see a leak to earth and blow fuses/trip the consumer unit, as happens in a normal situation when an internal transformer develops a short as occasionally happens with consumer gear? (apologies to any qualified electronics people reading this - if I'm wrong, PLEASE tell me and I'll edit accordingly!).

Apologies if I'm over-stepping the mark as it's obvious which unit Pinky is having a continued go at, but I swear I have nothing whatever to do with this item and have never tried one. I've only seen the large and heavy, cake-like doped tranny sitting on its Perspex base and a completed item all glued up ready to ship out, NOT the wiring, which would be done with very heavy SWG bus-wire and soldered up solidly.

[Macca]

. My new Karcher K5 pressure washer takes up the first 3 pages of a slim instruction manual with safety warnings. It's a glorified garden hose for heavens sake, not a lethal weapon. But it is considered responsible to make appropriate safety warnings.

.

It has 3 pages of safety warnings because Karcher don't want to get succesfully sued so they go to their legal division who come up with three pages of catch-all bumph that they figure will cover them as much as possible in the event of a claim against them. If there were no laws to consider they wouldn't even bother to put a warning and they wouldn't have a legal department either. That boiler plate is not there just because they are nice guys.

And I'm sure we can agree that if someone wanted to harm themselves with a pressure washer it would take them 5 seconds to figure out how and do it. Not a valid comparison

[struth]

lol. like the place container in oven for an hr at 300 c...warning the container and its contents will be hot!


as for doctors they often need pointing in the right direction....medicine is a vast subject these days and family gps only know so much. thats why they send you to a specialist

[Gazjam]

As someone who has installed a BPS system I find this thread quite interesting.
Had a quick Google and current Wiring regs (BS 7671:2008 Requirements for Electrical Installations: (17th Edition)
have an interesting say in this...

Since 2008 all new build properties have a legal requirement to have RCDs fitted.
Prior to 2008 there was no legal requirement to install RCDs in a property.

Interesting information here:
http://www.nhmf.co.uk/bestpractice/index.cfm?article=121

(and I quote)
"There are many changes from the 16th to 17th editions of the regulations, however perhaps the most significant with respect to dwellings, or installations that are for use by ordinary persons and not under the supervision of skilled or instructed persons, is that all socket outlets intended for general use shall be protected by a 30mA Residual Current Device. Also any socket outlets up to 32A supplying equipment outdoors shall be RCD protected. Previously the requirement for RCD protection only applied to socket outlets where it was likely that they could be used for equipment outdoors."

Whats interesting is that theres no legal requirement to "upgrade" the property if the electricity install was fitted prior to the 2008 regs coming in.
So still an area (potentially for a lot of people where common sense and informed choice needs to be excercised.

So if theres an RCD fitted, any discussion about the benefits/effects/harm by not having one is a bit academic really.

In my opinion the best course of action if your interested in fiting a BPS is to do nothing without consulting an electrician to either help or sign the work off.
Like a few of us have been saying, make an informed choice and use your common sense.

[Marco]

Hi Dave,


Marco, I have to say and with respect to Anthony TD, that your own valve amp is exceptionally well made and carefully thought out, judging by the pics you've posted in the past. His own current production shields the valves well I believe and you don't have kids and possibly don't let the cats anywhere near it.

Yup, on all accounts! All my kit and dedicated mains supply is housed in a separate listening room, whose door is shut at all times, until I seek access to the room. That’s why my levels of ‘risk assessment’, in terms of what you're outlining, are rather different from those of most others :)


Apologies if I'm over-stepping the mark as it's obvious which unit Pinky is having a continued go at…


Not necessarily… How you interpret what’s written, in that respect, is directly proportional to your knowledge of the ‘history’ in question - and of course the manufacturer of that unit isn’t guilty of similar behaviour himself against other products, if it suits his agenda? Yeah, right!

As they say: ‘people in glass houses shouldn’t throw stones’ ;)

Marco.

[BTH K10A]

For a good definitive opinion on the safety pro's and cons of using balanced mains you need not look futher than Hugh Robjohns response to a safety question on Sondonsound.

http://www.soundonsound.com/sos/nov06/articles/crosstalk_1106.htm

[Ali Tait]

Yep, have posted that link several times.

Agree with what is being said re. safety. If you are not confident about what you are doing, don't do it!

[Ali Tait]

BTW Gaz, the regs are now up to 18th edition.

[Oldpinkman]

Dave. You continue to miss the point. Amplifiers do (often) have a centre-tapped transformer to give a positive and negative rail

There are no circumstances in which you can plug a hoover into an amplifier, or a hedge trimmer, or a drill, or - an amplifier. It is that "plugging something into it" rather than the unit itself which is the issue. And mostly it is the lack of responsible safety warnings, and the opposite - outright untrue (potentially dangerous ) statements which concerned me.

That was why I took Maccas advice, copied and pasted to another forum, "if anyone has genuine safety concerns they should report them to the appropriate authorities". And that is what the authorities are investigating.

Statements like "can be used like any mains socket" are not my idea of an appropriate arse-covering safety warning. If you poke your finger (borrowing a screwdriver for the purpose - in the style of Ali's avatar) in an ordinary mains socket in my house - the rcd will trip. If you poke your finger in the same hole on the socket of a BMU you will get an electric shock and the RCD won't protect you.

Just say so - and people understand the risks. Making untrue statements like "the rcd on the household consumer unit will protect you just the same for a device plugged into a BMU" is just too stupid for words. Instead just say "RCD's are probably un-necessary for devices like HiFi and are more relevant for devices used outside or in bathrooms and kitchens, but if you want the protection of an RCD it will be necessary to fit an RCD to the output of the device as the household consumer unit rcd's will not provide any protection for devices plugged into this BPS .

How hard is that? :scratch:

[Oldpinkman]

It has 3 pages of safety warnings because Karcher don't want to get succesfully sued so they go to their legal division who come up with three pages of catch-all bumph that they figure will cover them as much as possible in the event of a claim against them. If there were no laws to consider they wouldn't even bother to put a warning and they wouldn't have a legal department either. That boiler plate is not there just because they are nice guys.

And I'm sure we can agree that if someone wanted to harm themselves with a pressure washer it would take them 5 seconds to figure out how and do it. Not a valid comparison

No Martin. That is the point. In todays litigious over-regulated world, if I manufactured a BPS or anything else for that matter, I would have a comprehensive set of arse-covering warnings. Nobody takes any notice of them. If you read the airlink Q&A they say

http://www.airlinktransformers.com/transformer-articles/balanced_power_supply_faqs/

Question 7) Are the power supplies compatible with equipment that are fitted with single pole power switch.

Answer: The balance power supply should be used with a double ploe switch to ensure that the equipment is fully isolated when the power is in the off position.

Yeah - right! Like I am going to have my Nad 3020 modified with double ploe (sic) switch if I want to use it in a BPS. But Airlink have covered their arse. They haven't made untrue potentially dangerous statements. A bit of common sense and responsible behaviour is all that's needed.

That, and the understanding of how the bloody things work. I guess if you don't understand how an rcd and a transformer work, you are likely to say things which are untrue. :doh:

[Oldpinkman]

As someone who has installed a BPS system I find this thread quite interesting.
Had a quick Google and current Wiring regs (BS 7671:2008 Requirements for Electrical Installations: (17th Edition)
have an interesting say in this...

Since 2008 all new build properties have a legal requirement to have RCDs fitted.
Prior to 2008 there was no legal requirement to install RCDs in a property.

Interesting information here:
http://www.nhmf.co.uk/bestpractice/index.cfm?article=121

(and I quote)
"There are many changes from the 16th to 17th editions of the regulations, however perhaps the most significant with respect to dwellings, or installations that are for use by ordinary persons and not under the supervision of skilled or instructed persons, is that all socket outlets intended for general use shall be protected by a 30mA Residual Current Device. Also any socket outlets up to 32A supplying equipment outdoors shall be RCD protected. Previously the requirement for RCD protection only applied to socket outlets where it was likely that they could be used for equipment outdoors."

Whats interesting is that theres no legal requirement to "upgrade" the property if the electricity install was fitted prior to the 2008 regs coming in.
So still an area (potentially for a lot of people where common sense and informed choice needs to be excercised.

So if theres an RCD fitted, any discussion about the benefits/effects/harm by not having one is a bit academic really.

In my opinion the best course of action if your interested in fiting a BPS is to do nothing without consulting an electrician to either help or sign the work off.
Like a few of us have been saying, make an informed choice and use your common sense.


That is interesting. It takes us a bit beyond understanding how these things work and using that understanding to be safe, into whether it is actually breaking the laws (however daft and OTT those laws may be) to "tamper with mains". The Trading Standards have raised a similar issue - effectively whether using a BPS changes the CE certification of a device plugged into it. If your NAD 3020 is compliant when it has a switch to turn off the power, and a fuse to cut power in the event of a fault, is it still compliant if you connect power in a way which by-passes the switch and fuse. Frankly , that's somewhere I don't want to go. I have taken a lot of ribbing for being the accountant - but today I am that. I am not today running a hifi company, so this is not currently my responsibility. My interest has been safety from the perspective of properly describing how the appliances work, and how they interact with the likes of RCD's and NOT trying to be expert in regulations and compliance.

But, as I alluded to with my insurance comment earlier, my discussions with the authorities have caused me to wonder about that question, and be circumspect about definitively describing something as "safe".

(Also to be fair, I have been interested in that "academic knowledge" aspect of correctly understanding how things work, and challenging people who clearly don't understand properly)

[Gazjam]

Its all good information Richard and these things are always a bit contentious. :)
A debate on electrical safety is never a bad thing.

[Oldpinkman]

Somebody asked for a circuit diagram. It's not very good - I'm not an artist either, but I think it just about does the job

http://i1315.photobucket.com/albums/t582/oldpinkman/rcdtestwiring_zpsc2577780.jpeg (http://s1315.photobucket.com/user/oldpinkman/media/rcdtestwiring_zpsc2577780.jpeg.html)

At the top is the plug with brown connected to live and blue to earth, showing how this makes a circuit between live and earth which we can use as a test device. The connection is made via a 500 ohm resistor.

Underneath shows why this test is equivalent to poking your finger in the mains (the thing rcd's are designed to protect you from)

Our basic circuit has power flowing between live and neutral via a load, passing through an RCD. The RCD detects the current in both live and neutral and trips if they are different by more than 30ma

see this link if you need a reminder about how

http://www.explainthatstuff.com/howrcdswork.html

Since Neutral is bonded to earth by the electricity supply, a connection from live to earth completes the circuit in the same way that a connection from live to neutral does. If our person (who is connected to earth) touches the wire carrying current (in this case the neutral wire) some of the current will flow to earth via the person, so not all the current will get back to neutral via the neutral wire. In this example we have assumed we had 5 amps on the circuit, and without our finger poked in there was 5 amps on L and 5 amps on N inside the RCD (not shown in this diagram)

But when the finger is poked in, half an amp - 500ma flows through the finger, so only 4.5 amps flows through neutral. Inside the RCD there is 5000ma on L and 4500ma on N - a difference of 500 ma which is more than the 30ma trip threshold, and the RCD trips.

It is not the fact that current flows to earth that trips the RCD, it is the fact it DOESNT flow to Neutral. And it doesnt flow to neutral because it flows to earth.

Rather than stick our finger in, we can create the same condition by getting current to flow through live but not neutral, but connecting our lightbulb between earth and live. In this circuit about 500ma flows through live (depends on the voltage 115 or 230) but zero ma flows through neutral (because the return is all through earth). So the rcd test simulates a short to earth through a human body. And trips the RCD

[Oldpinkman]

http://i1315.photobucket.com/albums/t582/oldpinkman/bpsrcdcircuit_zps38d6351d.jpeg (http://s1315.photobucket.com/user/oldpinkman/media/bpsrcdcircuit_zps38d6351d.jpeg.html)

This diagram shows why the RCD doesnt protect the same fault when it is on the output of a BPS. The BPS is a transformer - 2 circuits which are physically separated from each other, but coupled by electromagnetism. This simplified version assumes a lossless transformer, to keep the sums simple. In practice some of the power is not transferred from primary to secondary but lost.

In the Normal situation at the top of the picture, the current flows through the load from + to - in the secondary. This causes a current to flow from live to neutral in the primary. So we have 5A on live and 5A on neutral and the RCD doesnt trip

In the 2nd diagram somebody sticks their finger in live and makes a circuit to earth, which is equivalent to connecting to the centre tap 0v connection, because this too is connected to earth. So the circuit is completed with current flowing from + to 0v via the earth connection. This causes a current to flow in the primary (I have kept it to 5A which is a cockup - but I'm not redrawing it. Lossless it would need the secondary to be 10amp for 5 amp to flow in the primary, :doh:)

The point is not how much current flows because of the different number of windings in the transformer - the point is the current induced in the primary still flows from Live to neutral. The fact that the current in the secondary is flowing from + to 0v instead of + to - in the secondary changes how much current flows in the primary in total, but whatever that primary current is, it is the same in L as it is in N. In my diagram 5A L 5A N. So the RCD doesnt trip - even though that load to earth on the secondary is an electrocution.

Hopefully that makes it clear. But if it doesnt - don't worry. You don't need to understand that stuff. Just prove it with the test I outlined earlier. If the lamp connected live to earth glows when plugged into the BPS then that proves the theory is right, and the RCD on the primary is ineffective. This diagram just explains why

:cool:

[DSJR]

FFS Richard, YOU'RE the one missing the whole point!!!!! Who in their right mind sticks their finger into a mains socket, let alone delves inside an amp when it's connected up and switched on? ONLY DIY, manufacturing and service personnel, that's who.

I'm going to say this again - you have an agenda and are trying to do down a perfectly valid manufacturer who DOES give good after-care to his products and has researched the BMU, testing it in fault conditions. The unit is Perspex cased and has an earth plane, as all his products do.

Look, for the last time, electronic gear uses power supplies, which do a very similar thing internally to a BMU. They have mains leads with fuses in the plug (yes, even NVA - my current batch of mains cables for AP20's and 10's have 5A fuses fitted as standard!!!) and a light bulb across one leg may well have the same impedance as an amp circuit across each 'leg' of the supply for all I or we know.

These arguments are becoming circular and others here have tried to make you see that your arguments may well not apply in the real world when a BMU is used for audio equipment AND NOTHING ELSE!!!!! I mean, with a bit of imagination, a flexible hose from a vacuum cleaner could be used for all 'sorts' of things apart from prime function, especially if you use the circular brush attachment on the end (:eyebrows:). By implication, used the way not intended, injury to certain private parts could ensue and that's not so different from your scenario of some numpty putting fingers in a power socket (the BMU would be 120V anyway so less dangerous if you really want to be pedantic about it.

Apologies to all. Everyone else is bored with this I think and although some education on electrical safety can only be a good thing, this thread is turning into a one-man crusade. The fact that few of us know for certain the pros and cons (due to lack of deep understanding about the subject) only inflates the issue, as the ones that know seem to have given up already as a bad job :( Just leave it be FFS!

P.S. I'm informed that BMU's are routinely used in pro audio circles. Is this correct?

[Joe]

I've come to the concusion that it's best to let trolls die of hunger.

[Marco]

Let’s cut the ‘heat’ here, chaps, and stick to discussing the products, not the personalities behind them, or I’ll be getting jiggy with the delete button. Therefore, if you continue in that vein, don’t be surprised if your posts are removed.

If you don’t like this thread, then avoid it, simples. Ta!

Marco.

[Desmo]

Everyone ... is bored with this I think and although some education on electrical safety can only be a good thing,.... :( Just leave it be FFS!


+1 :zzz::zzz::zzz:

[Oldpinkman]

Gosh. It's all gone quiet on here. It seems my diagram explaining why an RCD on the input can provide no protection for an earth leak on the output has now been understood by all, and nobody is any longer disputing that Ali and I were right in stating that an RCD on the input of a BPS can provide no protection for anything plugged into that BPS.

Maybe that doesn't matter. Maybe you would be protected by a fuse or mcb (miniature circuit breaker). And anyway, if its not protected by a fuse, its only 115v not 230v so that's maybe not a problem. I can say daft things like that because I am only an accountant - but if I were a product manufacturer being investigated by trading standards, whose attention has been drawn to forum posts made by that manufacturer, I would be a bit more circumspect. Still - its a free country. :)

No, come on seriously - it does matter. Lets have a look at a useful reference on the subject - the BEAMA's very own "The RCD Handbook"

http://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CCMQFjAA&url=http%3A%2F%2Fwww.beama.org.uk%2Fdownload.cfm%2 Fdocid%2F3FA319A6-4159-4816-87188608E386D98D&ei=u6WOVJG8EZfVaoPHgugK&usg=AFQjCNFxeaHqCxqtPNLdLheLsnIti55_aQ&sig2=Norb0Fcv6kQVP5M1AiLTOg&bvm=bv.81828268,d.d2s

It's a bit of a monster pdf, but it has a nice overview for non-specialists at the front. Let's consider some sections

The use of electricity is so much a part of every day life that it is often taken for
granted and the risks associated with its use at home and at work are
underestimated or misunderstood.
In a typical year, 19 people die in the UK from electric shock in the home and a similar
number die in other buildings. Fire brigades are called to 10,000 incidents attributed to
electrical faults, of which half are in the home. These domestic fires result in about 600
serious injuries and 23 deaths.
Residual Current Devices (RCDs) are electrical devices which afford a very high degree of
protection against the risks of electrocution and fire caused by earth faults. However, they
are not a panacea for all installation problems; it is therefore important to understand what
they can and cannot do. Furthermore, the different types of RCD available on the market
can be confusing.

“What is an RCD?”
An RCD is a device that is designed to provide protection against electrocution or
electrical fires by cutting off the flow of electricity automatically, or actuating an alarm,
when it senses a ‘leakage’ of electric current from a circuit.
To appreciate the importance of an RCD it is helpful to understand how much electrical
energy it takes to kill a human being. The smallest fuse used in a normal electric plug is 3
Amps; it takes less than one twentieth of that current to kill an adult in less than one tenth
of a second.

I'll let you read the rest for yourselves. But I need to emphasise a VERY IMPORTANT POINT made by an engineer on another forum, who clearly knows what he is talking about. "It's volts that jolts, but mills that kills". The issue here is amps not voltage. Voltage is slightly relevant because of Ohms law (A=V/R) which we learned in an earlier post. For any given resistance, then the current from 115v will be half that from 230v. But a quite small current connected across the heart can kill. Let's quote from the experts again

It only requires a very small continuous electric current – 40mA (a twenty-fifth
of an amp) or more – flowing through the human body to cause irreversible
damage to the normal cardiac cycle (‘ventricular fibrillation’) or death
(‘electrocution’). When somebody comes into direct contact with mains
voltage and earth, the current flowing through the body, is of the order of
230mA (just under a quarter of an amp).

Now they are assuming a 230v system here - so in a 115v system the current flowing through the body would be 115ma - but that is still much more than 40ma. (Read the next bit with caution - let's not dispute what this authority on the subject says, but just out of interest, they have assumed an electrocution resistance for the human body of 1000 ohms (1Kohm). 230v/1000 ohms gives 0.23A = 230ma. The resistance of the human body varies - it's minimum resistance across the wet internal organs is 30 ohms - and its maximum resistance on the dry calloused soles of feet could be megaohms. But - 1000 ohms is the figure used in a typical electrocution. The impedance of our 60w bulb is close enough.)

Clearly though, if we go with 1000ohms as the resistance of a human body, then the current on an electrocution from a 115v BPS would be 115ma - which wouldn't even trip the fuse protecting my Pip, never mind an MCB probably rated at 15A or 30A. One wonders where some people get their daft ideas from. :scratch:

Never mind - RCD's save lives. A BPS will remove the protection of a household RCD from any device plugged into the BPS - as our simple 60w bulb test proved. If you want to preserve the life-saving protection of an RCD when using a BPS, fit one on the outputs. If an doubt, consult a properly qualified engineer - as I did! :)

[Oldpinkman]

Oh - while I was doing my long one, I see we picked up some activity after all. I think my long (but not difficult) post covers the points.

[Marco]

Oh - while I was doing my long one...

Did you manage to flush it or was it one of those stubborn ‘floaters'? :D

Anyway, are we done with this topic now, or have you further pearls of wisdom to impart? I ask because we’re in danger of things becoming somewhat repetitive and circular.

Marco.

[Oldpinkman]

Did you manage to flush it or was it one of those stubborn ‘floaters'? :D

Anyway, are we done with this topic now, or have you further pearls of wisdom to impart? I ask because we’re in danger of things becoming somewhat repetitive and circular.

Marco.

I was just concerned to clear up this confusion about what kills people. 40ma - which you can get from 115v every bit as much as you can get it from 230v. I think the long post covered it - have a read of the introduction to the pdf - it explains the whole thing well, and ain't complicated.

I think we have established that RCD's in the house are not going to work to protect from a fault or hazard on anything plugged into a BPS (although that had been disputed until I got my crayons out and showed-off my skills as an artist. Surprising really, cos its pretty elementary stuff)

We just needed to make the point that an RCD is THE lifesaver, and a fuse or mcb will not do that job because they need MUCH more than 40ma (which is lethal) before they blow.

Job done :cool:

[Marco]

I was just concerned to clear up this confusion about what kills people. 40ma - which you can get from 115v every bit as much as you can get it from 230v. I think the long post covered it - have a read of the introduction to the pdf - it explains the whole thing well, and ain't complicated.

I think we have established that RCD's in the house are not going to work to protect from a fault or hazard on anything plugged into a BPS (although that had been disputed until I got my crayons out and showed-off my skills as an artist. Surprising really, cos its pretty elementary stuff)

We just needed to make the point that an RCD is THE lifesaver, and a fuse or mcb will not do that job because they need MUCH more than 40ma (which is lethal) before they blow.

Job done :cool:

Excellent. You’ll be pleased to know that a professional I’ve consulted on the matter agrees with you, stating, I quote:


what old pinky is saying as far as the sasfety aspect of the BMU is correct, the mains side (primary) of the transformer will only see a current diffrence if there was a fault in the equipment on the secondary side, due to there not being a direct contact/connection between the primary winding and secondary load.


;)

Marco.

[struth]

kiss me goodnight sergent major;)

[Oldpinkman]

Excellent. You’ll be pleased to know that a professional I’ve consulted on the matter agrees with you, stating, I quote:



;)

Marco.

Thanks - I'm sure you must have guessed by now - as my wife who is a teacher would put it "Richard - are you sure this is all your own work???"

I've been rumbled - I consulted an expert too :D

[Marco]

Really?? Well, shockarooney!! :eek:

Gosh, there was me thinking that an accountant was trying to advise on technical issues relating to the mains supply. I guess you’d need to be pretty dim to arrive at that conclusion, eh? But that’s me - ever the daftee! ;)

Marco.

[Joe]

So does this work the other way round; ie if we ask about accountancy, does an electrician have to respond?

[r100]

BMUs: Would somebody please post a schematic for these showing earthing arrangements? Thanks.

the real test of what is advanced here would be to post all this on diyaudio.com. That would really be fun.

[Gazjam]

The main point regarding BPS systems is that they have safety features build it to cut off the supply when (however unlikely) a fault condition occurs.
Double pole RCBOs fitted to primary and secondary legs covers you with this.

All else is banter and (hopefully not) agenda driven :)

[DSJR]

In the meantime and back in the real world, rather than the 'possible,' have a look at this - looks as if it has RCD's too, although they're not in the 'circuit diagram.'

http://www.airlinktransformers.com/balanced_power_supply/technical-notes/

[Marco]

the real test of what is advanced here would be to post all this on diyaudio.com. That would really be fun.

:eyebrows:

That’s where the pronouncements of the ‘Wiki-trained experts’ out there would be shown up for what they are ;)


So does this work the other way round; ie if we ask about accountancy, does an electrician have to respond?

Only if it’s a Tuesday.

Marco.

[Oldpinkman]

In the meantime and back in the real world, rather than the 'possible,' have a look at this - looks as if it has RCD's too, although they're not in the 'circuit diagram.'

http://www.airlinktransformers.com/balanced_power_supply/technical-notes/

Airlink offer output RCD's as an optional extra, which is why they are not on the circuit diagram. http://www.airlinktransformers.com/transformer_product_upgrades/protection_upgrade/

Trust me Dave, you want to avoid thread drift into a "how they work" discussion. ;)

[r100]

:eyebrows:

That’s where the pronouncements of the ‘Wiki-trained experts’ out there would be shown up for what they are ;)

Marco.

:lol: true ! and everyone could participate. What a show !

[Gazjam]

Airlink offer output RCD's as an optional extra, which is why they are not on the circuit diagram. http://www.airlinktransformers.com/transformer_product_upgrades/protection_upgrade/

Trust me Dave, you want to avoid thread drift into a "how they work" discussion. ;)

And based on good advice I added these to my Airlink BPS.
Wouldnt get one without them.

[Marco]

Sammy has some more to say on the subject, in response to what’s being written elsewhere on the matter:


Not sure i am reading him correctly, but he should know that i am saying without a shadow of a doubt (unless he really is thick) that unless the BMU's secondary he is producing has a direct contact with the live on the primary, which it doesn't because it’s a transformer, with totally seperate primary, and secondary windings, then the RCD in the consumer unit will not see or detect a leakage to earth by something connected to the BMU's secondary, (unless in an extreeme case there was a short in the primary and secondary windings of the BMU) therefore, it will not trip it under this fault condition. the only way to make sure this type of unit could be made safe is to fit additional RCDs on the secondary winding of the BMU, where the load is!


Furthermore (when asked about Class 2 regs):


With all due respect, it wont make any diffrence what regs he classifies it into, it still wont be safe under the conditions i have explained above, double insulated means that there is no direct connection between the consumer and the innards of the device, i.e; it’s in a plastic box, therefore with no metal connection between the electronics inside the box and the consumer. Anyone interested in his explanation on safety, ask him seen as he is self certifying it, and that the device is primarily intended for use with Audio/video components, and equipment,does it comply with Standard EN 60065, and if it doesn't, ask him to explain why.


More on the matter from Sammy’s wee brother, Jimmy:


The truth of the matter is that what Pinky says (again and again and again .....! ) is actually quite correct. Where Pinky goes astray is in coming up with unlikely scenarios: only a complete fool would touch any part of circuitry exposed to the mains without disconnection.

So the BMU is perfectly safe to use as directed: in the event of a catastrophic failure of any device plugged into the BMU, the enormous current drawn in the secondary winding would require a similar (actually half) current to be drawn by the primary, which of course would exceed the over-current rating of any circuit breaker (or the rupture current of a fuse) in the consumer unit protecting the socket into which the BMU is plugged.

Where there is disagreement is to the extent that the BMU compromises the inherent safety provided by an RCB (residual current circuit breaker). Under normal conditions were one to touch a live conductor, current flow through your body and to earth, would mean the current flowing in both the live and neutral wires would be unbalanced. An RCBO is set to trip out if this current difference is 30mA or more; and will do so within 3 half-cycles (30ms). To be killed by electrocution you need something like 100mA flowing through you for 100ms, so RCBs are set on the safety side of caution.

What happens however with a BMU with a centre-tapped secondary connected to earth, is if you now touch a live terminal (now at a maximum of 120V) current could still flow through your body via the ground, completeing the circuit around one half of the secondary winding. This means that the current flow in the secondary is now unbalanced (just as it would be without a BMU), but because a double-pole RCB has not been fitted to the secondary there is no protection against electric shock. It is simply untrue (despite what RD claims) that the RCB in the consumer unit would trip under these conditions, because the current flowing on the primary side is not unbalanced.

However to put this in perspective: you would have to be pretty damned stupid to touch a live connection without fully disconnecting it from the mains, and if you did so the shock you would receive would be at 120V; which is unlikely to be lethal. So in that respect RD gets away with this "what if" scenario. To be absolutely safe, any sensible manufacturer would fit a double pole RCB on the seconday side of a BMU.


Interesting - apart from anything else, what about this compliance then with Standard EN 60065?

Marco.

[Oldpinkman]

And I get accused of long posts!

Basically agreeing. I deliberately stayed out of the CE aspect - although I doubt trading standards will (if they get round to it). The point about shocks is not sticking fingers in to deliberately get electrocuted - although Ali's avatar provides a nice reminder of precisely why people with families like the protection of RCD's.

The issue is that a BPS might not be used with HiFi only. Your teenage daughter might come down after a shower with a towel wrapped round her and dry her hair with a hairdryer plugged into it. Particularly if there are no warnings to the effect of "only to be used with HiFi" on the device itself. Accordingly, it might be used like any other multi-adaptor. And accordingly there is as much fire risk and electrocution risk as anywhere domestically that electricity is used. So according to the BEAMA RCD handbook - that is 19 deaths in the UK pa from electrocution and 10,000 incidents (5000 in domestic houses) pa where fire brigade are called attributed to electrical faults, leading to 600 serious injuries, and 23 deaths. It's not hard to read the first 6 or so pages. After all the disinformation produced I would recommend anybody wanting to make an informed decision about safety to take the 10 minutes needed to read it.

That same report states that 40ma is enough to be lethal - I am in no mood to argue with them. We are splitting hairs a bit - it doesn't matter whether we choose 40ma or 100ma no fuse or circuit breaker is going to offer any protection. At least on this forum folk are talking amps not volts.

The point was a very simple one - if you appreciate the benefits of RCD's and you want to use a BPS - you need to fit the RCD's on the output. And if you manufacture the devices, I would have thought you would want responsibly to draw attention to that fact. Not publicly , repeatedly make statements denying it. (Albeit trying to fog it up a bit by confusing the devices by calling them all "trips". )

[Marco]

The point was a very simple one - if you appreciate the benefits of RCD's and you want to use a BPS - you need to fit the RCD's on the output.

In a nutshell, that’s it, which is also what Sammy was saying earlier:


The only way to make sure this type of unit could be made safe is to fit additional RCDs on the secondary winding of the BMU, where the load is!


So the question to ask is why doesn’t the BMU in question have additional RCDs on its secondary winding? Also, as ‘Sammy’ said:


anyone interested in his explanation on safety, ask him seen as he is self certifying it, and that the device is primarily intended for use with Audio/video components, and equipment, does it comply with Standard EN 60065, and if it doesn't, ask him to explain why.


I would like to see an answer to that from the manufacturer, and confirmation or not if it does meet such compliance, together with the other issue raised above. Once those matters have been answered satisfactorily, the discussion can be brought to an end and we can form our own conclusions.

Marco.

[Joe]

'the BMU is perfectly safe to use as directed'

There you go, end of story, nothing to see here, move along.

[Marco]

Not quite. Nothing like selective quoting, eh Joe?

Read the rest of what was written (especially this bit: "This means that the current flow in the secondary is now unbalanced (just as it would be without a BMU), but because a double-pole RCB has not been fitted to the secondary there is no protection against electric shock.”), and you’ll see there are still plenty of ‘grey areas’ for concern (specifically what I’ve also highlighted in blue)!

Until an acceptable answer is provided to those two questions, this discussion is not over.

Marco.

[Oldpinkman]

'the NVA BMU is perfectly safe to use as directed'

There you go, end of story, nothing to see here, move along.

This thread was not about just one device. The discussion originated with regard to Ali's advice about the devices he and Gazjam built. It considers safety aspects generically. Since you raised the NVA product the direction says "can be used like any mains socket" on the ebay advert. I feel that might be interpreted as "feel free to plug your hair-dryer or hedge trimmer into it"

It would probably be more fair to say "The BMU in question could be safe to use if appropriate instructions and safety warnings were followed, instead of ridiculous denials of electrical facts". But the important principle remains - regardless of who makes it, or what class of device it is, if you want to have the protection of an RCD - a device which, (and I quote the BEAMA guide) "are electrical devices which afford a very high degree of protection against the risks of electrocution and fire caused by earth faults"

if you want that protection for anything plugged into a BPS - you are going to have to fit RCD's on its output. You don't have to want that protection. I think a responsible manufacturer should make clear the truth about the fact that using the BPS means that RCD protection is not available for any device plugged into it. They should also point out that only one of its 2 live legs is protected by a fuse (or a device on-off switch) - in the way Airlink do.

Note - the use of an RCBO (or rather 2 of them) on the output gives you both an RCD and a fuse on the output which covers both of the safety issues in a couple of devices costing no more than £20 a piece. They are usually all plastic parts on their exposed user interface,

http://www.tlc-direct.co.uk/Images/Products/size_3/CB61SLASHB10630.JPG

Oh - and since you might not know - the BEAMA are "BEAMA is the independent expert knowledge base and forum for the electrotechnical industry for the UK and across Europe. Representing over 300 manufacturing companies in the electrotechnical sector, the organisation has significant influence over UK and international political, standardisation and commercial policy. " www.beama.org.uk

[Oldpinkman]

I have been accused of producing ridiculous scenarios. Time and again people are treating a BPS as the device which is dangerous. It is the things plugged into it which are dangerous. And they are made dangerous because the protection of an RCD is removed

Since folk may not choose to read the BEAMA RCD guide, this is from page 22.

The Toddler
A two year old, left playing with his battery powered toy, was found by his father who
initially thought he was asleep. Sticking out of the live and earth of a socket-outlet were
two skewers that he had presumably tried to use to power his toy, with tragic
consequences.
In the foregoing cases the use of an RCD would have prevented a fatal electric
shock. In the following case the use of an RCD did prevent a serious electric
shock which could have proved fatal.

As a parent, I don't appreciate this flippant "oh how dangerous is an amplifier" whining. Explain to my why the toddler in the example above (whose parents now have RCD's fitted to avoid this tragedy) - why would that toddler know its ok to poke his skewers in a wall socket, but its not ok to poke them in a BMU?????? :steam:

Any other parents out there?

[Marco]

Also, if the manufacturer of the BMU in question states that because the rest of the equipment he makes is double-insulated, does that mean that the BMU is only to be used with said equipment (or other equipment that is also double-insulated)?

If that’s the case, then he needs to make that fact absolutely clear to anyone who is interested in purchasing a BMU from him.

Marco.

[Joe]

This is frankly going into the realm of the bizarre. Anything can be dangerous if not properly used. Most sane people realise that leaving skewers around for toddlers to play with is a bad idea, even without electrical equipment in the vicinity. Also they realise that it's a bad idea to mix water and electricity in most circumstances.

[Oldpinkman]

This is frankly going into the realm of the bizarre. Anything can be dangerous if not properly used. Most sane people realise that leaving skewers around for toddlers to play with is a bad idea, even without electrical equipment in the vicinity. Also they realise that it's a bad idea to mix water and electricity in most circumstances.

So, what you're saying Joe, is rcds are pointless and unnecessary and anyone installing them is creating a nanny state. The law requiring them to be installed in new homes for the protection of the vulnerable like the young and the elderly should be repealed and replaced by a law requiring people to be more responsible and stop having accidents. You are presumably not a parent.

I wouldn't go standing for parliament on that manifesto either. Nor taking that attitude with safety authorities.

And here's your hypocrisy and bullshit challenge. 19 people die every year on average in the UK from electrocution. More from electrically caused fires. How many deaths from cadmium poisoning occurred in the Eu in the last decade? If we want to discuss ludicrous and bizarre.

[Joe]

So, what you're saying Joe, is rcds are pointless and unnecessary and anyone installing them is creating a nanny state. The law requiring them to be installed in new homes for the protection of the vulnerable like the young and the elderly should be repealed and replaced by a law requiring people to be more responsible and stop having accidents. You are presumably not a parent.
.

I am a parent. Strangely enough my children made it into adulthood, but then I didn't allow them to stick skewers into electrical sockets as toddlers or take hairdryers into the shower as teenagers. For that matter, I didn't let my frail aged parents loose in the garden with electric hedge trimmers, or employ incompetent chimney sweeps. Guess I was just lucky, really.

[Oldpinkman]

I am a parent. Strangely enough my children made it into adulthood, but then I didn't allow them to stick skewers into electrical sockets as toddlers or take hairdryers into the shower as teenagers. For that matter, I didn't let my frail aged parents loose in the garden with electric hedge trimmers, or employ incompetent chimney sweeps. Guess I was just lucky, really.

Ducking the cadmium question I see. It's OK - you can phone a friend. ;)

I must introduce you to my friend John whose 11 year old son was killed by a passing car for you to explain to him how if he had parented properly his son would be alive today. Yes - you have been lucky in that respect.

[Gazjam]

This is frankly going into the realm of the bizarre. Anything can be dangerous if not properly used. Most sane people realise that leaving skewers around for toddlers to play with is a bad idea, even without electrical equipment in the vicinity. Also they realise that it's a bad idea to mix water and electricity in most circumstances.

Too true...
Another one is to never drink a cold glass of water when eating a hot sausage roll...
Your mouth will get greasy...

[Joe]

Ducking the cadmium question I see. It's OK - you can phone a friend. ;)

Is this about Cadmium? I don't know anything about that, or what relevance it has to doing stupid things around electricity.

[Joe]

Too true...
Another one is to never drink a cold glass of water when eating a hot sausage roll...
Your mouth will get greasy...yuk.

The one that nearly killed me was answering the phone when I was eating peanuts. There should have been a health warning to that effect on either phone, or packet of peanuts, or both.

[Gazjam]

Ducking the cadmium question I see. It's OK - you can phone a friend. ;)

I must introduce you to my friend John whose 11 year old son was killed by a passing car for you to explain to him how if he had parented properly his son would be alive today. Yes - you have been lucky in that respect.

Fucks sake Richard, thats a bit of a glib comment?
Sure your friend has other things on his mind....

[struth]

OK you 2, Richard & Joe, Cut that crap out or those kind of posts will be deleted.

[Ninanina]

Can I ask a question 'very loosely' connected with this thread...? ;)

[Gazjam]

Who are you askin'? :)

[Joe]

Who are you askin'? :)

Ghostbusters!

[Ninanina]

Well anyone really..

Does anyone know if eBay listings are allowed to quote/dis other manufacturers in their discription? and maybe quote people that don't know they have been quoted ?

Just asking like...;)

[Joe]

Well anyone really..

Does anyone know if eBay listings are allowed to quote/dis other manufacturers in their discription? and maybe quote people that don't know they have been quoted ?

Just asking like...;)

I'm not sure I fully understand the question, but it sounds like something you need to check with eBay and/or a lawyer, depending on what you're intending to say in your listing.

[Ninanina]

I'm not sure I fully understand the question, but it sounds like something you need to check with eBay and/or a lawyer, depending on what you're intending to say in your listing.

It's not a listing I want to place it's a listing placed by someone else ;)

[struth]

As these remarks have no relevance to the topic I take it you would rather they be moved to a more suitable place Bev?

[Ninanina]

As these remarks have no relevance to the topic I take it you would rather they be moved to a more suitable place Bev?

Grant the question is 'loosely' to do with this thread.. I can't say anymore as I don't think I'm allowed to... if you know what I mean :doh:

[struth]

Best not to then;)

[anthonyTD]

http://www.airlinktransformers.com/balanced_power_supply/
Anyone interested in a decent BMU at a realy good price, go for the largest VA rated version you can afford to minimise the affect of increasing the mains impedance, their larger versions also have RCD's built into the secondaries, so no issue with safety.
A...

[r100]

http://www.airlinktransformers.com/balanced_power_supply/
Anyone interested in a decent BMU at a realy good price, go for the largest VA rated version you can afford to minimise the affect of increasing the mains impedance, their larger versions also have RCD's built into the secondaries, so no issue with safety.
A...
They are not expensive either [emoji12] ..
and we may finally be getting to a conclusion ?

[anthonyTD]

Indeed,
However, from experience i have found in many cases the most affective way of lowering the potential of mains born noise getting into your system is to keep the mains impedance as low as posible rather than increasing it, unless of course its a passive mains filter, which by its very nature will increase the mains impedance due to the inline chokes, but as its a filter, and as long as its designed right, the positives should way out way the negatives. Balanced mains supplies do have their positives when used in the type of enviroments they were designed for, and in regular audio equipment and systems they will have an affect, whether that affect is a positive one ??? IMHO that would be mainly down to the end users opinion more than fact...
A...
They are not expensive either [emoji12] ..
and we may finally be getting to a conclusion ?

[Joe]

Balanced mains supplies do have their positives when used in the type of enviroments they were designed for, and in regular audio equipment and systems they will have an affect, whether that affect is a positive one ??? IMHO that would be mainly down to the end users opinion more than fact...
A...

But isn't that true of almost everything in audio? You'll either hear a difference or you won't when switching/adding components. If you hear a difference, it's either going to be to your taste or not. There are no absolutes here.

[anthonyTD]

:)

But isn't that true of almost everything in audio? You'll either hear a difference or you won't when switching/adding components. If you hear a difference, it's either going to be to your taste or not. There are no absolutes here.

[Oldpinkman]

:)

Oh dear. I'd been trying to avoid thread drift into what they do and how they do it because I just find it funny when people talk nonsense about how things work, rather than saying they like what they hear. I have been happy to let "secret recipes" and "sprinkled with fairy dust" go since nobody got killed by believing that nonsense. The function of an RCD and its role in saving lives and fires is a different matter.

The appalling attitude taken by some people regarding safety legislation, recognised best practice, and industry experts like BEAMA makes me inclined to a little thread-drift. On the subject of Isolation transformers. Not least, because its only slight thread drift - the term is used loosely and in different contexts. Some shadowy figure suggested isolation transformers were used in bathrooms for safety so a BPS must be safe

Not true. The isolation transformers,whether balanced or not, have a floating ground on the secondary. As such you cannot get electrocuted by making a path to true earth by coming into contact with the live wires on the secondary - there is no circuit. However, by virtue of grounding the secondary centre tap to true earth, to enable a path to earth for class I devices plugged into it - the ground no longer floats and is bonded to true earth. So the transformer is not isolating in that sense any more, and it isn't safe to use in the bathroom in the way that one with a floating earth would be.

The other nonsense was the article about common mode rejection, and "isolating transformers" being any and every transformer. Actually - the article very clearly says quite the opposite. "Contrary to popular opinion, isolation transformers cannot effectively isolate a circuit from noise caused by grounds without the intelligent use of proper shielding and ground design.". It goes on to discuss why capacitive coupling in the transformer limits its high frequency band pass - its effectiveness as a low pass filter. Keeping it short it says "isolation transformers" are the answer. But contrary to the beliefs of some, it is not true to say "ALL transformers are isolation transformers" . In this context they mean "isolation transformers with electrostatic shields". I'm so sorry guys, but this brings us back to Faraday shields and their grounding. Suffice to say for now that the erudite article had in mind devices more akin to these than an off the shelf toroidal http://www.shepherdindia.in/ultra-transformer.html

Sometimes it helps to read an article rather than just link to it. But "isolation transformer" can have at least 3 different contexts or meanings. To the extent it isolates a current flowing to earth on the secondary, from the RCD detection devices on the primary - a BPS is "isolating". A transfomer designed for safety testing is "isolating" by virtue of a floating ground not bonded to true earth. And for common mode noise rejection without high frequency leakage, we are talking about a specialist built device with additional internal shielding (more faraday cages) and a construction which usually has the windings physically separated more than in a normal off the shelf toroidal.

But nobody ever got killed mis-understanding common mode noise rejection, so I wasn't so fussed about it. They might well get killed thinking a BPS with its secondary ground bonded to earth was an "isolating transformer" and using it in a bathroom as "safe" (unless of course it is fitted with RCD's on the output ;))

[Joe]

Wow. A simple smiley gets a 600-word response. What was that saying about brevity being the soul of wit?

[Marco]

I made it 602.

Marco.

[Joe]

I made it 602.

Marco.

Damn! Now I'll have to start counting again!

[anthonyTD]

I have no idea what that was about either :scratch:
My smiley was a response to one post that Joe put up and i get this ?
A...

[Marco]

Pinky unfortunately has the habit of using 500 words, when only 5 are needed.

Marco.

[Markiii]

Grant the question is 'loosely' to do with this thread.. I can't say anymore as I don't think I'm allowed to... if you know what I mean :doh:

Really should be moved then,

[Oldpinkman]

I have no idea what that was about either :scratch:
My smiley was a response to one post that Joe put up and i get this ?
A...
Anthony. Sorry. That wasn't directed at you. The matters I referred to will be recognised by those making the mistakes. Your reference to issues other than safety just released my inhibitions

[struth]

Ok, this thread has in my opinion finished being informative and is now in danger of becoming circular. I will thank everyone for their opinions, and after all that is the reason for these discussions; so that people can make an informed choice. So, on that point I am going to close it.