"Do not use an extension lead!"

[JBR]

The mother-in-law bought an electric fire (from B&Q) and, as she was already having some work done, asked the gas man to connect it up for her. Now I am not criticising gas men generally, I know one or two good blokes, but this chap was happy to use a standard multi-socket extension lead as the nearest wall socket was too far away for the fire's lead and fitted plug.
The other day, while the wife was visiting her mother, she could smell burning from the plug inserted in a socket of the extension lead. She sensibly unplugged the extension lead from the wall socket (this end was perfectly cool) and felt the fire's plug was "red hot". After waiting for it to cool, she tried to extract it from the extension lead socket, but it seemed to be welded in!
She called in an electrician, who suggested that he could attach a new wall socket near to the fire, wired from the existing wall socket, and run the cables in a trunk along the wall or under the floorboards.
All well and good, but why should standard mains cables be safer than an extension lead? The only difference I can see is that the interim connections could be 'weak points', which would explain the 'red hot' plug being welded in. Is this the reason for B&Q instructions not to use extension leads, although the cabling in a lead and a fitted cable are likely to be similar in specifications?
Incidentally, the fire is still within a three-year warranty. Unfortunately, the documentation supplied by B&Q states, "Do not use an extension lead!", which, of course, will have made the warranty now invalid.
I have thought that, although we have no claim on B&Q, we could cut off the damaged plug and attach another and continue to use the fire. However, doing this would also invalidate the warranty, I assume, and the electrician also advised against doing this,
Any advice or comments, and even criticisms! are very welcome.

 

[EFLImpudence]

Of course you can change the plug if the original is damaged.

 

[Mottie]

Is this the reason for B&Q instructions not to use extension leads,

Normally, if you use an extension lead on a coil and it’s a high demand unit that it’s powering, the coil could heat up. You are supposed to uncoil the whole length.

 

[Murdochcat]

It’s best not to use extension leads with heaters …. Seen far too many issues outlined above in my time to say it’s safe or sensible

 

[JBR]

Of course you can change the plug if the original is damaged.

Thanks for your advice. Personally, I would do that, but the electrician who will extend the wall socket has said not to. I'll leave it up to the wife and the mother-in-law! They'll decide whether it's worth buying a new fire.

 

[JBR]

Normally, if you use an extension lead on a coil and it’s a high demand unit that it’s powering, the coil could heat up. You are supposed to uncoil the whole length.

Thanks for your advice. No, I know better than that and always uncoil the lead. In the case of the mother-in-law, it wasn't a coiled lead anyway.

 

[JBR]

It’s best not to use extension leads with heaters …. Seen far too many issues outlined above in my time to say it’s safe or sensible

Thanks for your advice. Yes, I can understand that, although we have a fan heater which may be used with an extension lead, but this is not 3Kw and is only used for short periods under supervision.
As I said earlier, if the cables are the same as the ones which would be used to extend a socket, I assume the weak points are the temporary connections: the plugs and sockets.

 

[bernardgreen]

The receptacles in the sockets on ready made extension lead often have the minimum area of contact with the pins in the appliance plug, This results in poor electrical contact which causes heating of receptacle and pin.

 

[ericmark]

I typical extension lead has a thermal overload

which should ensure if it over heats, it will switch off. One shown is only rated 10 amp. This one is rated 13 amp with 1.25 mm² cable again with cut out, but standard plug, it says in advert trade rated, so one would assume it can be moved from place to place, and as it is 25 meters long it may not cause the fuse to rupture within the required time with a line to earth fault, so where I work it would be required to have a RCD plug on it as one can't guarantee it will be plugged into a RCD protected socket.

This is also an extension lead but not long enough to worry about RCD protection, it says heavy duty cable, but does not stipulate size, so we have no idea if it will or will not take a 13 amp load for an extended time. This is also an extension lead advertised as for a caravan so should be 25 meters long and 2.5 mm² although it does not say how thick the cable is, but this is clearly able to take a 16 amp load for a long time.

So the question has to be what extension lead? I know refrigeration units often say do not use an extension lead, as volt drop can cause them to fail to start fast enough and so cause an overload, only when using an inverter drive is there no significant inrush so volt drop is no longer a problem. Old fluorescent lights with magnetic ballasts could also have a problem, but most items today should be able to use an extension lead if the lead is matched to the use.

The 13 amp plug contains a fuse, the way they work is they get hot, that hot the wire inside the fuse melts, so the plug needs to dissipate that heat, it does this in two ways, one into the ambient air, and two into the socket, so a 13 amp plug should be in free air, or forced air when supplying some thing like an oven. The cable of the extension should also be in free air, with a cable anti trip cover normally black as it can absorb the heat better, and designed for the job, OK, but cover with a carpet so no one trips, and the cable can over heat.

So in the case in question we have no idea was the plug faulty or the extension? We have no idea of the quality of either, so to say without some knowledge of the product extension leads are bad is wrong, some are bad, we see youtube videos of tests on extension leads showing some could not safely carry 3 amp, but that does not mean they are all bad.

 

[JBR]

The receptacles in the sockets on ready made extension lead often have the minimum area of contact with the pins in the appliance plug, This results in poor electrical contact which causes heating of receptacle and pin.

Yes. Exactly as I suspected. I might try to examine both when they have been replaced.

 

[JBR]

I typical extension lead View attachment 333386 has a thermal overload View attachment 333387 which should ensure if it over heats, it will switch off. One shown is only rated 10 a

So in the case in question we have no idea was the plug faulty or the extension? We have no idea of the quality of either, so to say without some knowledge of the product extension leads are bad is wrong, some are bad, we see youtube videos of tests on extension leads showing some could not safely carry 3 amp, but that does not mean they are all bad.

Yes, our coiled lead has a thermal overload button and I think (without checking) is rated at 13A.

When the wife goes over again and gets the electrician to add a new wall socket, I'll ask her to cut off the plug from the fire and bring back it and the extension lead. I want to try to get the two separated and open them both up, and I'll bet that at least one of the contacts in either the plug or the extension lead socket (or both) will show heat damage. If that is the case, I'll suggest adding a new plug on the cable of the fire and see if the fire works properly.

 

[ericmark]

Some of the multi plug type extensions I bought while living in Hong Kong did have some rather flimsy contacts, but the ones bought in UK seem much better, but do not allow used of 16, 13, and 5 amp plugs both with and without earths, so you win some and loose some.

But if the connector does not have a fuse they do run cooler.

 

[JBR]

Some of the multi plug type extensions I bought while living in Hong Kong did have some rather flimsy contacts, but the ones bought in UK seem much better, but do not allow used of 16, 13, and 5 amp plugs both with and without earths, so you win some and loose some.

But if the connector does not have a fuse they do run cooler.

But what plugs do they accept?

 

[ericmark]

Only 13 amp not a variety, the Hong Kong type I could at the same time have a 5 amp and a 13 amp plugged in, yes rather bad ambiguity little like the sign which said "Beware of the man eating haggis" on the old A road to Scotland.

 

[JBR]

Only 13 amp not a variety, the Hong Kong type I could at the same time have a 5 amp and a 13 amp plugged in, yes rather bad ambiguity little like the sign which said "Beware of the man eating haggis" on the old A road to Scotland.

Ah, I see. I misunderstood. Like those sockets that can take American and Australian plugs, for example.