I just had the fuse in my PSU power lead go bang, it was a 5amp fuse.  I have two brand new replacements in my 'bit n bobs' box that I can use, but they are both 13amp. Would it be safe to use them on a 550watt PSU, or should I get a replacement 5amp fuse?

Depends on what you mean by safe It'll function just fine, but if it does overload it potentially requires nearly 3x the juice to do so before the fuse cuts in.

I'd suggest putting in the correct fuse as that is what it has been designed for, but in all reality I expect there to be no issue using a higher value as it's on the mains side, not the DC side anyway!

The thing is I'm pretty sure that the two replacement 13amp leads are the ones supplied to me with my last two Antec PSUs, the 5amp lead was from another PSU I used years ago. I wonder why they are supplying 13amp leads, when 5amp is adequate?

Anyway I'm taking your advice and going to get a new 5amp fuse.

I've always thought they used 13amps tbh! Every lead I've ever used has been 13amp for PCs/monitors when its not been the supplied lead.

A fuse blows for a reason, if you put to large fuse in it will not protect on the other hand if it was a fuse of to low value it will blow for that reason and the PSU is not faulty.

Sorry, I didn't realise it was the kettle lead you were talking about, I thought it was the one that was in the back of the PSU.

In that case I'm sure 13A should be fine, as Clock'd says 13A is standard for kettle leads

550watts is 2.3amps

but... there'll be a surge of more than that when you first power on... so a 3amp fuse is a bit small

plus... computer power supplies must be one of the most protected things around... they have plenty of cut outs built into them etc.. so i wouldn't worry :-)

Well, having just read this on another forum:

QuoteAccording to Ohm's Law ( I remember something from my Physics lessons all those years ago!):

Current = Power/Voltage

So divide the wattage rating of your power supply by 240 to get the size of fuse required - 3A should be sufficient for a PC, coping with up to 720W which would be a pretty meaty supply for a computer.

This equation doesn't apply to equipment with motors in which require an initial high startup current, eg vacuum cleaners, washing machines. I don't think that applies to PCs, although someone please correct me if I'm wrong.

It seems 13amps is standard for a kettle lead, but not what a PC should need. I would imagine that most modern PSUs have circuitry that protect the PSU regardless of the fuse in the plug though?


edit: what knighty just said

The fuse in the plug is actually only there to protect the flex, not the PSU (or anything)....So the danger is melting the cable due to a too greater load on the wires, and the fuse won't blow.