A

Adskee

Hope I'm posting this in the correct place, couldn't find a "new post" button in the DIY forum.

I have built a 100l kettle using a large pot and an immersion heater. The original heater I tried was 5.5kw, wired using 2.5mm cable to a standard plug. The plug got very hot after 3 minutes. After some discussions and research, I determined that trying to pull 23a down through a standard 13a socket was a very bad idea.

So I downgraded to a 3kw heater - 12.5a, should be fine. Same cable, same plug got very hot again.

So then I thought it might be the wiring in the plug (or the plug itself) so I bought a moulded plug with 1.5mm cable. Cut it down to 2m in length so the run wasn't too long. This time, the cable started getting warm (very slightly) after a 3-4 minutes. I left it running for 10 minutes, by which point the cable was warmer, the plug wasn't warm yet but the bit where the cable leaves the plug was getting warm too. I unpplugged at this point and the Live and Neutral pins were pretty hot. Too hot to touch. The socket felt fine.

My question is, why is this getting so hot? I've tried it on different sockets, one in my house, one in the new shed (which is where the kettle will live) so I don't think it's faulty sockets. I've used two different plugs and two different cables. I need this running for about 1.5 - 2 hours at a time so if it's hot after 10 mins it's a worry.

Will it reach a level of heat and stop or just keep getting hotter and hotter until my house melts? From what I've read online (not always a good idea), I should get a little heat but this setup should be OK as it's under 13a.

Where am I going wrong? Cheap heating element??
 
A decent plug top like the old school MK ones and a bit of 1.5mm butyl. TBH I wouldn't like this as a permanent solution and would be better if you had a dedicated 16A radial with double pole switch.
 
A decent plug top like the old school MK ones and a bit of 1.5mm butyl. TBH I wouldn't like this as a permanent solution and would be better if you had a dedicated 16A radial with double pole switch.

Had that in my house for years (old mk plug top to) , had CH so it was only for back up. I considered wiring dedicated radial but never got round to it.
 
3kW is fine, in theory, on a 13A plug with 1.5mm² flex. It will get warm due to resistance in the fuse and contacts, but will not carry on getting warmer once it has reached equilibrium. However, if either the plug or the socket is not of best quality and in good condition with tight contacts and clean pins, there is a tendency to overheat at 3kW. For this reason it is not a recommended method for making permanent connections to appliances with a continuous load of 3kW.

When you say 2 flex, do you mean the number of cores

No, he said ^2 which is shorthand for squared if you can't type a superscript ² on your keyboard.
 
A decent plug top like the old school MK ones and a bit of 1.5mm butyl. TBH I wouldn't like this as a permanent solution and would be better if you had a dedicated 16A radial with double pole switch.

If you want to try the old school plug try http://uk.farnell.com/mk-electric/646whi/plug-safety-13a-white/dp/107754

and you will need a decent make of socket, not the 99p special from screwfix....

and for cable try http://uk.farnell.com/pro-power/h07rnf3-1-5/cable-3core-1-5mm-per-m/dp/1494813
 
The more current you draw through a cable the warmer it will get. If you constantly pull 12.5A through a system designed to handle 13A it will be a lot more noticeable than, say, boiling a domestic kettle. Obviously this will put more strain on the wiring in the same way as redlining your car's engine.

My question would be why do you need a homemade 100 litre kettle in your shed?
 

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3kw Heater on a 13a Socket
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