Quick fuse question

[realysm42]

I know this will sound really daft but you don't know unless you ask; I've bought a new mains lead for my amp (The Audio Asylum mains cord from Mains Cables R Us) and it came with a 10amp fuse in it, the question is is it okay to put a 13amp fuse in the plug?

My friend told me that it's infact better to have a higher rated fuse in a plug, but it doesn't sound right to me.

In a more extreme situation, would it be okay to use one in a 5amp rated product (such as a pc)?

Cheers guys, I know I could Google it but you lot seem to explain things really well!

[Ali Tait]

For safety's sake, use the correctly rated fuse for the component you are feeding. It is most certainly NOT better to have a higher rated fuse than that required, you would be leaving yourself open to possible component damage and even injury or death. People are far to blase about electricity IMHO.

[realysm42]

Thanks for the input, I appreciate it.

[Ali Tait]

No problem. Perhaps I sounded a bit short, if I did please accept an apology. I work in the high voltage industry and have been to seven funereals in the last 25 years of people who were killed by electricity, so I tend to be a little evengelical about it.

[DSJR]

As I understand it, the fuse in the mains plug protects the mains cable. I hope I'm correct in this, but typical IEC mains leads are usually rated at 10A and a higher current rating example has three horizontal pins as used in some Krell power amps (I think from memory). The gear itself will probably have much lower rated fuses - less then 5A I suspect..

Quick story. A client had a system with mono power amps kept in a well ventilated cupboard. He only used the system at weekends, turning everything on Friday evening and off on Sunday bedtime.. In the previous year, several UK manufacturers had experienced random mains fuse blowing in their amps (Audiolab being one, AVI another) and couldn't explain it as nothing seemed wrong with the gear. One of these manufacturers up-rated the mains fuse on the back panel to 5A slo-blow.

One weekend overnight, one of these amps developed a fault condition (the rectifier went short). The fuse didn't blow and the amp caught fire inside. Thankfully the metal case contained it and the molten charred mess within, but the amp was a write-off and it took a lot of persuading for the chap to get a free replacement, the hinge point being the fuse that didn't blow which was authorised by the manufacturer...

Forgive the ramble above, but going from a clean 10A fuse to a 13A one isn't going to make a real difference unless you've cleaned the contacts by replacing it.. I'd always stick to safety myself..

[The Grand Wazoo]

....the fuse in the mains plug protects the mains cable.

I often see this said but it's rather misleading actually, because the implication is that a mains cable is easily replaced.
However, the fuse isn't protecting the cable, it's protecting you, your loved ones, your home and possessions from destruction in the case of an accident to the mains cable.

When you put it like that, it seems rather more like it should be taken seriously by sticking to using a correctly rated fuse.

[The Black Adder]

as far as I'm now aware so long as your equipment is fused you can run an un-fused lead to it so long as the distribution block is fused to 13A.

[Reid Malenfant]

You may be assuming too much ;) The 13A fuse in the distribution block may not blow even if there is a short on the mains cable, you see it depends on the cable rating & obviously if it is somehow damaged.

I wouldn't even contemplate it unless each cable was at least 1.25mm^2, in which case the fuse would go very quickly indeed if the cable was somehow shorted out through damage. In the case of a 3Amp rated figure of eight lead it may well not go fast enough to stop something very nasty from occuring :eek:

[worrasf]

You may be assuming too much ;) The 13A fuse in the distribution block may not blow even if there is a short on the mains cable, you see it depends on the cable rating & obviously if it is somehow damaged.
Seconded. I cut through the mains cable on my circular saw last week - didn't blow the fuse in the plug (3 amp), extension lead or distribution unit :eek:

Steve

[The Black Adder]

I understand that, what I didn't say was that my fuse board is a very modern RCD unit so that would trip anyway.

[Reid Malenfant]

Not on a two core cable it wouldn't ;)

[realysm42]

@Ali Tait - I'd rather you were to the point; atleast I have a genuin eunderstanding of the gravity of my choices so ta mate.

Seems I've sparked quite a debate about such a seemingly simple question :P

[Reid Malenfant]

Martin, I'm sure you'll get used to seeing this kind of thing on here - it's nothing new ;)

[Ali Tait]

Perhaps, but hairs are being split really. The safest way is to stick to the correct rating of fuse for the component being supplied. It was something that did the rounds a few years ago that a higher rated fuse sounds better, but I've never noticed a difference.

[keiths]

I think it was Naim who started all that "always fit 13amp fuses" stuff, wasn't it?

[The Black Adder]

Not on a two core cable it wouldn't ;)

I don't run 2 core. Always earth.

[Reid Malenfant]

Ok, but some equipment only has a two core supply because it's "double insulated"...

[DSJR]

I think it was Naim who started all that "always fit 13amp fuses" stuff, wasn't it?

It went further into 15A round pin un-fused plugs and sockets run off a spur from the fuse box. Can't remember if this spur would have been fused if done by the user.. In the shop, our upstairs dem room had sixteen double unswitched sockets wired on a ring, returning to the fuse box downstairs. There was a 15A isolation switch in the dem room and a 30A switch in the fuse-meter cupboard which the electricians felt ok at the time (1982). All gone now I think.

[MartinT]

a higher current rating example has three horizontal pins as used in some Krell power amps (I think from memory)

That's a 16A (or 20A) Hubbell connector as used in my Chord power amp, too. Bastard to get a third party plug to fit as the socket is so deeply recessed.