Fuses - again

[Roger Hayter]

Especially if you use a transparent architrave.

[Scott]

I noticed that with two computer cables both fused at 10A. I replaced the printer with 5A (claimed rating 2.5A). I don't know what to use for the PC itself because of the array of components involved. Thinking about 7A :-)

[Fredxx]

If I was the leccy I would leave as is with cable visible and tell the landlord to sort out the safe zones properly; where if he was to cover the cable it would no longer be compliant.

[spuorgelgoog]

They're used in *very* secure buildings where any tampering with the wiring or concealment of devices must be visible.

Owain

[tabbypurr]

A few things have either changed or been more widely recognised since the 1940s.

Back then appliances were routinely not suitably fused & designed to safely deal with internal faults. The plug fuse was a safety device for the appliance as well as the lead. Now it's usually not, it only remains so for historic appliances.

Leads were often very thin, basically what we now call speaker wire. Using under 3A fuses is wise if such wire is used.

Now most people are not expected to have any clue what value of fuse an appliance can or should run on - and don't. In the 40s it was expected that people would have some idea on this.

The financial saving of having fewer choices is now widely recognised & appreciated. Stocking 3 & 13A is cheaper than stocking 1, 2, 3, 5, 7, 10, 13A.

Ultimately yes, it's always safer to use the fuse that best suits each appliance. For historic goods that matters far more. I don't have any real data on what difference that approach can make to fire & death stats.

NT

[tabbypurr]

PCs typically take an amp or less. Only high power systems eat more. While '500w' PSUs are moderately common, they're normally not 500w, and a computer that eats 500w is an unusual animal. Hype rules.

NT

[Steve Walker]

Not unusual for a gaming PC's CPU to use 120W when working hard and a pair of graphics card to take 300W between them. That doesn't leave a lot out of 500W for the motherboard, RAM, hard-disks/SSDs, etc.

SteveW

[tabbypurr]

Sure, such systems are in use. Even those don't run flat out all the time. And mains fuses can provide double rated current for a long time.

NT

[Scott]

So my initial 'guesstimate' of 7A might be okay then (allowing for surges)?

[tabbypurr]

any mains fuse from 2A or 3A up is ok, PCs are all modern appliances. 7A is far above necessary of course. The inrush current duration is too short to worry such a fuse.

[Scott]

Thanks.

[Tufnell Park]

It might run for a while but will get very hot!

[Dave Plowman (News)]

Because to know what the correct size fuse is, you'd need to know the cable size. Somewhat easier with removable plugs, but guesswork with moulded types.

And perhaps most only want to get the thing working again, so will fit any fuse they have to hand, or can buy easily. Most likely 13 amp.

[Scott]

How is it 'guesswork'? The manufacturer must know when they select the fuse.

Okay, but any sensible person would replace like for like. You could say the same about 3A fuses. By your logic all electrical appliances should be fitted with a 13A cable just in case someone decides to fit a 13A fuse at a later stage.

[spuorgelgoog]

Leads were also longer as people had fewer sockets. Remember the days you'd get a good 2 or 3 yards of flex on a table lamp.

Now all EU appliances are supposed to be okay with unfused plugs as that's normal in Europe, and leads are shorter to provide less resistance so a higher rated fuse/MCB blows quickly enough.

Lucky Golden Hedgehog leads from China are still on the thin side though.

Owain

[Dave Plowman (News)]

And you can be sure it hasn't been replaced?

But many ain't sensible. Hence small cables not being used with fitted 13 amp plugs these days.

[Scott]

If the purpose of the fuse is to protect the flex (as is often said), does this mean all flexes can cope with 16 amps (European radial circuit)?

[Mike Clarke]

That works on the assumption that most people are sensible.

There are many who would happily keep trying the next larger size fuse until it 'worked'.

[Scott]

But according to your logic the fuse might be replaced so I think you are contradicting yourself here.

You could still end up with a 3 amp cable and 13 amp fuse, unless you are saying all cables are 13 amp.

I cannot see how the manufacturer fitting a higher rated fuse assists safety in any way.

[Scott]

So all appliances are designed to be safe with a 13 amp fuse? The flex on the lamp I bought from John Lewis does not look to me that it could carry 13 amps but I could be wrong. I won't be trying it out.