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G6Tanuki · 1st Jul 2019, 3:15 pm

Part of the issue is switch-on surges: a 'beefy' amplifier can draw a surprisingly large surge-current if the power-switch is closed at the right point in the AC cycle. Anti-surge fuses in the amp itself are specified to handle this but there are no anti-surge fuses available for fitting in the plugs themselves.

A 13A fuse in the plug avoids such 'nuisance blowing', even though it may seem vastly overrated for steady-state working.

It's not just amplifiers etc. that can have issues like this: at a previous gig the company contracted to PAT all the IT equipment discovered to their horror that all the computer-monitors were fitted with 13A fuses in the plugs, despite the monitors - big CRT ones - being rated to take 300 Watts. So they swapped all the 13A fuses for 3A ones 'to be safe'. After a few days we started having monitors failing to power-up in the morning, the issue being that though they only took an Amp or so in steady-operation, when powered-on the degauss system activated and this caused quite an impressive current-spike for a mains-cycle or two. Though this didn't blow the fuse the first couple of times it sufficiently weakened it that it was doomed to failure.

I sent someone out with the company credit-card to scour the neighbourhood and buy up every 13A fuse they could find. We needed a couple of hundred of them!

1st Jul 2019, 3:15 pm	#34
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,998	Re: 13 amp fuse for 1.5mm mains flex? Part of the issue is switch-on surges: a 'beefy' amplifier can draw a surprisingly large surge-current if the power-switch is closed at the right point in the AC cycle. Anti-surge fuses in the amp itself are specified to handle this but there are no anti-surge fuses available for fitting in the plugs themselves. A 13A fuse in the plug avoids such 'nuisance blowing', even though it may seem vastly overrated for steady-state working. It's not just amplifiers etc. that can have issues like this: at a previous gig the company contracted to PAT all the IT equipment discovered to their horror that all the computer-monitors were fitted with 13A fuses in the plugs, despite the monitors - big CRT ones - being rated to take 300 Watts. So they swapped all the 13A fuses for 3A ones 'to be safe'. After a few days we started having monitors failing to power-up in the morning, the issue being that though they only took an Amp or so in steady-operation, when powered-on the degauss system activated and this caused quite an impressive current-spike for a mains-cycle or two. Though this didn't blow the fuse the first couple of times it sufficiently weakened it that it was doomed to failure. I sent someone out with the company credit-card to scour the neighbourhood and buy up every 13A fuse they could find. We needed a couple of hundred of them!