Running a 2.5KW heater through plug socket

[Foliage]

Gingerbread Man said:

I was working on a domestic building site once. Think they were doing a bit of a refurbished. I remember picking up an extension lead to move it out of the way, but promptly dropping it due to the heat of the thing.

I don't remember what they had plugged into it. Really was hot though.

Ive seen 'cheap' 25m coil extension extension leads that wouldn't unwind anymore due to the outer sheath being melted together...

[sidekickdmr]

How does that work with drum extention leads?



I have a 50 meter one so I can reach the end of the garden, thats on a drum so its "coiled" and never had it overheat despite using angle grinders and cement mixers on it.

[Sheepshanks]

All that jazz said:

Has the plug lifted away from the socket due to melting or was it not pushed fully home in the first place?

I'm sure blokes do it as well, but living in a house full of girls they're terrible for only half pushing plugs in. The other thing that horrifies me is people blindly pushing plugs in and catching an iPhone charging cable between the plug and socket.

Edited by Sheepshanks on Friday 2nd December 10:40

[All that jazz]

It would normally have been all the way home but I can see a bit of a gap in the original pic I posted which is unusual for me. The whole lot was completely melted in the socket and I pretty much had to chisel the plug out to get the 2nd pic.

[Peanut Gallery]

sidekickdmr said:

How does that work with drum extention leads?



I have a 50 meter one so I can reach the end of the garden, thats on a drum so its "coiled" and never had it overheat despite using angle grinders and cement mixers on it.

It was one of these I warmed up... - the first cement mixer on google is 0.5kw, the first 9" angle grinder is 0.75kw, I plugged in 2kw. (heaters pull a fair whack)

The rolls from Tesco claim 0.69kw wound, 2.3kw unwound.

Thank you for the youtube channel S11Steve, seen some of his stuff before, I hate to imagine his leccy bill for some of his experiments!

[IanCress]

Foliage said:

Ive seen 'cheap' 25m coil extension extension leads that wouldn't unwind anymore due to the outer sheath being melted together...

Saw it happen in an office I worked at about 10 years ago. Massive 25m reel of cable not unwound with a large fan heater plugged in to it.

All the electrics tripped in one side of the office and I was asked to go find out why. Turns out the reel of cable had literally all melted in to one lump. It was smoking and smelled terrible.

[Sheepshanks]

Peanut Gallery said:

It was one of these I warmed up... - the first cement mixer on google is 0.5kw, the first 9" angle grinder is 0.75kw, I plugged in 2kw. (heaters pull a fair whack)

Generally with tools etc you're using them in fairly short bursts so you're likely to get away with it even if the ratings are marginal.

OTOH heaters are often just left on for extended periods.

[hab1966]

sidekickdmr said:

How does that work with drum extention leads?



I have a 50 meter one so I can reach the end of the garden, thats on a drum so its "coiled" and never had it overheat despite using angle grinders and cement mixers on it.

The cable reel pictured, has a thermal cut-off to protect against overloading when fully reeled and is also downrated when fully wound to 720W as opposed to 3120W when fully unwound.

http://www.masterplug-proxt.com/public/downloads/t...

Edited by hab1966 on Friday 2nd December 12:47

[Alucidnation]

battered said:

A twin socket on a ring will handle 2 x 13A if it's wired 2.5 T&E in a ring, and a total of 20A if it's on a single radial circuit of 1 x 2.5 T&E. A ring main 2.5 T&E will handle 30A total.

Not all double sockets are able to take 26A. Many are 13A across the two sockets.

2.5mm2 will handle up to 26A in a radial circuit, however, with a RFC the load is generally distributed between the legs which is why RFC's are protected at 32A.

[Sheepshanks]

Alucidnation said:

battered said:

A twin socket on a ring will handle 2 x 13A if it's wired 2.5 T&E in a ring, and a total of 20A if it's on a single radial circuit of 1 x 2.5 T&E. A ring main 2.5 T&E will handle 30A total.

Not all double sockets are able to take 26A. Many are 13A across the two sockets.

2.5mm2 will handle up to 26A in a radial circuit, however, with a RFC the load is generally distributed between the legs which is why RFC's are protected at 32A.

The British Standard for double sockets is for 20A total - and even that's with quite a hefty temperature rise.

[Alucidnation]

Correct, as the 20A comes from the product standard eg to be able to withstand a 20A load for 4 hours against a 54C temperature rise and not overheat with 14A on one side and 6 on the other.

However, there are (were) some manufacturers whose products exceeded this standard.

[RYH64E]

If a plug is getting hot it's because there's a bad connection somewhere, either in the plug or between the plug and socket, it's the high resistance that's the culprit rather than the load.

I'm not an electrician, but I think the problem with coiled extension lead melting under load is due to induction heating.

[ruggedscotty]

The reason a cable reel heats up when coiled isnt due to induction heating.

When the reel is wound up there is little chance of any heat being dissipated as it is created so it is concentrated and the temperature rises very fast in that reel.

For example...

any cable has a resistance, if you have a resistance you have a volt drop across the cable, now if you have a current flowing and a voltage drop then you have power dont you ? P = I x V...

Where does that power go ? HEAT !

a few watts over 25 meters unwound the cable may get warm but it has the opportunity to dissipate to the surroundings. wound up it doesnt and it will heat up.