Storage Heater trips RCD after it starts to heatup

26 Nov 2012
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United Kingdom
Hi, my first time here.

3 years ago after buying my flat I replaced an old Tricity 3.4KW storage heater with a new Sunhouse Automatic 3.4KW. I also have an old Tricity 2.4KW storage heater.

Sunhouse was connected using a 2.5mm heat resistant cable via what I later found out was a 13A led switch which gradually died (well fried really) as it was getting hot and was replaced with a 20amp switch which seemed to get warm rather than hot. The 2.4KW tricity has never had switch heating problems but I also changed its 13A to 20A.

Both heaters are separately connected into a dedicated 63A 2 Module Double Pole RCD consumer unit made by CED with each heater having its own 32A-SP MCB.

Right from the start if the input dial on the Sunhouse was set to 5 or over (1-6) the main RCD would trip. So I kept it to under 5 and all was well. Recently I noticed that the 20A switch on the Sunhouse is also getting very hot and consequently tripping the RCD at input settings even less than 5.

I am now thinking of putting a 32A switch on the sunhouse as from my school physics the heating switch means resistance and assume a 32A switch may resolve the problem.

Finally both heaters are connected to the consumer unit using external cables not embedded within the walls which must have been done by the previous owners. And that the flat used to have the old wire fuses which I had replaced with 2 consumer units, one for the heaters and one for the rest of the flat.

Does this problem ring a bell for anyone?
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The 20A switch should not be getting warm or hot. When this happens, it is either due to the switch being a poor quality item, or more likely the wires are loose.
If the wires have overheated previously, the copper will have softened, making it impossible to connect a new switch satisfactorily.
Changing to a 32A switch is not necessary and will not solve the problem.

Storage heaters would normally have 16A or possibly 20A circuits. 32A is wrong.

If the cables are on the surface, you probably don't need an RCD anyway.
However just removing the RCD is not the answer, as there is obviously one or more faults which need to be repaired.
So one could bypass the storage heater's CU and RCD!!! hem very tempting thanks flameport.

I had the 32A switch on last night with 2 inches cut from the old 2.5mm cable which showed signs of heating and rubber fusion. Believe it or not checked it every 2-3 hours until the Econ7.5 period was over. The switch stayed cool and I managed a 4.8 setting. tonight I will go the distance and set it to its max 6 with the other heater (2.4KW) also on full.

The question is if this works out ok for a few days can I consider the problem history, or buy a good quality 20A switch and try that for a few nights. Ah,yes will also open the heater checking and tightening all of its elements just in case. Hope its not going to be a case of ifs not broken don't fix it.
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