Fuse wire question

beautiful_ravens

Hello,
In my shed theres an old fuse box with two old style wire fuses in it and a trip switch.
Theres a cable that goes to the house fuse box which is related to the sockets in the shed, it has its own small trip indoors.
We have a dodgy light switch which someone didnt know about and turned on, and it always blows this one wire-fuse which does the lights in the shed. We turned the sockets back on via the house switch, but the lights are connected up to this fuse-wire thing.

What size fuse wire is it likely to be?
I watched the electrician sort it out when the same thing happened last year, and Im sure youtube can refresh my memory, but I dont know what fuse wire it is, and what will happen if I put the wrong size in there?

Ebe_Scrooge

For lighting circuits, the fuse wire should be 5 amp. If you put a lower-rated wire in ( e.g. 3 amp ), no big deal, it'll just blow even more often. Put a 13 amp wire in, odds on it'll stop blowing - but you'll burn the shed down. Seriously, you must NEVER replace any kind of fuse with a higher rated one than what the circuit's designed for.


That aside, you need to sort out the cause of the problem. It's all well and good replacing fuses, but until you sort out the root cause you're on a hiding to nothing.


When you say it's a "dodgy switch" - what do you mean, exactly ? If this really is the cause of the problem, then replacing it with a new switch will cost maybe a couple of quid and is an easy DIY job - just remember to turn off the current to the appropriate circuit before you start doing anything !!!

beautiful_ravens

Thanks Ebe Scrooge,

5 amp, then. If theres any wire left in the fuse, I'll compare the size before I go ahead.

This is an old rented place, with a lot of DIY by previous occupants...

Theres a really old light switch that did a couple of lights in the car shed next to the shed, and if you switch it on, everything outside goes, and one of the kids forgot about that. Its covered up now so no more switching on.

Its not an urgent thing really, Ive lived without those lights since the last time they went. Even if I tell the landlord, it could be months before their very laid back electrician actually turns up. In fact he does know, but he didnt think it was urgent enough to fix and he was on his way home, last job of the day etc.

But I do want to replace this fuse wire, the outdoor light isn't working and its pretty dark getting to the shed/freezers/car. I watched electrician do it last time - undo screws, take out old wire, thread new wire through middle section, tighten screws, trim ends of wire....?

I will definitely turn off the entire electric supply, not taking any chances there.

Le_Kirk

On fuses there is normally a coloured "blob" on the front - white, blue and red which tells you the fuse rating. The white would be 5 amp (as advised above for lighting circuits), blue for 15 amp for power circuits and red for 30 amp like cooker circuits.

Risteard

Ebe_Scrooge wrote: »

If you put a lower-rated wire in ( e.g. 3 amp ), no big deal, it'll just blow even more often. Put a 13 amp wire in, odds on it'll stop blowing

I'd be curious where you source fuse wire for BS 3036 rewireable fuses with a 3A or 13A rating from...

Mr.Generous

Risteard is right (as always) fuse wire I've seen is 5, 15 and 30 amp, although it almost certainly goes higher.

I just wanted to add it's probably not a dodgy switch, things are rarely that simple. The switch is connecting something up that has a dead short, or something consuming above the fuse capacity. If it blows straight away much more likely a dead short. That really shouldn't be left. If its rented you should be asking landlord to get it sorted.

I am amazed Risteard didn't insist you got a minimum of three fully qualified highly paid electricians in to suck their teeth and tell you what a big job it was to isolate the loose wires where the old security light rusted away or whatever....

Ebe_Scrooge

Risteard wrote: »

I'd be curious where you source fuse wire for BS 3036 rewireable fuses with a 3A or 13A rating from...

Risteard, I might have known you'd be along, bisecting rabbits. No, I'm not a qualified electrician, unlike yourself. The point I was trying to make was, you can safely substitute a LOWER rated fuse wire, but you must never substitute a HIGHER rate fuse wire.

Cue the discussion about whether 240v is low voltage or not .....

There we are then.

Risteard

Ebe_Scrooge wrote: »

Cue the discussion about whether 240v is low voltage or not .....

It is. That isn't debateable. Although you may be interested to note that the single phase supply voltage is actually 230V, not 240V. (It hasn't been 240V for around 22 years.)

ic

You might want to replace with these, to save having to replace fuse wire - http://www.toolstation.com/shop/Electrical/d190/Wylex+Consumer+Units/sd2615/Wylex+Plug+in+Breaker+B+Type/p38609

However as above, figure out why it keeps blowing. That's a problem that shouldn't be ignored.

Ebe_Scrooge

Risteard wrote: »

It is. That isn't debateable. Although you may be interested to note that the single phase supply voltage is actually 230V, not 240V. (It hasn't been 240V for around 22 years.)

Go on then, I'm game. 240 volts ( or 230 ) is pretty low compared to the distribution network of 400 KV - or the millions of volts produced by a lightning strike. Still enough to kill you though. Please realise you're offering advice on here to ordinary people in the UK. 240 volts is enough to kill you, or at the very least give you a whole heap of pain. Context is everything. Yes, to someone working for the Electricity Board ( yeah, I know, it no longer exists, but a family member used to work for them ), 240 volts is low. To the average householder, 240v is potentially lethal, and is the "highest" voltage they're likely to encounter in their everyday life. 12V - as in "low-voltage" plinth lights, or whatever, is safe to mess with. As is 1.5 volts, or thereabouts, produced by a battery.

Right, now onto voltage versus current - your car runs on 12 volts but the current can kill you if you touch the HT leads....

Apodemus

Ebe_Scrooge wrote: »

Right, now onto voltage versus current - your car runs on 12 volts but the current can kill you if you touch the HT leads....

Oh yes, if we're dissecting Lagomorphs, one of the few things to have survived the 40 years since my last physics lesson is that it is the amps that kill you not the volts!:)