Very hot spur switch for underfloor heating

sebtomato

Hi,

I have electric underfloor heating in my living room/kitchen (one cable, wattage unknown) and when switched on, the spur switch (with a 13A fuse) on the wall becomes very hot, particularly the fuse section, and there is a bitter smell (like something melting).

I also have underfloor heating in other rooms, and the spur switches become warm but not hot.

I am thinking that maybe the heating cable in the living room/kitchen uses more current than other smaller rooms, and therefore could exceed 13A, or the heating is somehow getting transferred to the switch.

Maybe the spur switch should be replaced by a 20amp double pole switch? The electric board for that room/cable has a 20A contactor and a 16A circuit breaker.

Any ideas?
Thanks,
Seb

muckybutt

sebtomato wrote: »

Hi,

I have electric underfloor heating in my living room/kitchen (one cable, wattage unknown) and when switched on, the spur switch (with a 13A fuse) on the wall becomes very hot, particularly the fuse section, and there is a bitter smell (like something melting).

I also have underfloor heating in other rooms, and the spur switches become warm but not hot.

I am thinking that maybe the heating cable in the living room/kitchen uses more current than other smaller rooms, and therefore could exceed 13A, or the heating is somehow getting transferred to the switch.

Maybe the spur switch should be replaced by a 20amp double pole switch? The electric board for that room/cable has a 20A contactor and a 16A circuit breaker.

Any ideas?
Thanks,
Seb

It is normal for spurs supplying high current to get warm, however if you can smell burning and the spur is excessively hot then there could well be something amiss inside the spur like a loose wire.

If you feel confident, turn the electric off at the fuse board, undo the screws on the spur, then with a flat blade screwdriver tighten all the screws on the terminals in the back.

If one of the terminals has been a bit slack then you might well see a cable that has burnt, this will need stripping back and reconnecting.

I would NOT swap it to a 20A double pole switch, the 13A spur is there for a reason, to protect the heating wiring !

If you feel at all unsure about anything or not confident in having a look at the electrics then seek professional help from a registered electrician.

Ectophile

If it's a standard 13A fused connection unit (FCU), then I would be inclined to throw it away and buy a new one. They are not expensive, and if the old one has overheated, then it may never be right again.

sebtomato

It's a standard fused spur switch, so I am happy to replace it, but just want to make sure that a fused spur switch is appropriate for a large UFH zone, as some posts on the web have mentioned that a 20A double pole switch could be more appropriate and also there is already a dedicated 16A circuit breaker so not sure if another fuse is required.

w50nky

If you can borrow an amp clamp style meter you should be able to find the current drawn by this circuit. You will then be able to work out the wattage. This info will determine if the 13 amp fused spur is underrated or not. You could also measure the resistance of the circuit and calculate from this too.

If you are not competent then best ask professional help of course.