Thermostatic panel heaters

[Martin606]

Hi all

I have just completed an electrical installation consisting of 2 ring circuits, 3 lighting circuits, fire alarm circuit and a heating circuit. All went well apart from the heating circuit.....

I have installed 2 electric thermostatic panel heaters, a 500w and a 750w one. They are in two offices and within 10m of the distribution board. The total load therefore is about 5.5A. I decided on a B6 MCB, 1.5mm twin&earth cable on a radial circuit and connected then via individual FCUs. I used a 3A fuse on the 500w and a 5A fuse on the 750w heater.
All dead testing , continuity, insulation resistance, polarity etc was all ok. Live testing was also ok.

My problem is this....
As soon as the 750w heater asks for power, i.e. turning the thermostat up, it trips the RCD but MCB does not trip. I did try a bigger MCB but same response.

I have spoken with technical support at Dimplex and told them the wiring design. They advise it could be a faulty heater and to return it.
Before I do this does anyone else have any other thoughts as to why this would happen...

I am probably missing something really simple but can someone please advise as soon as possible.

Thanks

 

[Leesparkykent]

Dodgy heater.

 

[westward10]

I would go for the replacement and see what happens.

 

[static zap]

--A well earthed metal sheet-- (Sheet is a good word)
Not sure about dimplex but some cheap ones not much more than a metal sheet with " Electric blanket wire"
Held down by alloy tape .
Usualy get a nice hole in tape if no RCD !
(I was very dissapointed - cheap in china ? )
Tech has moved on - 3M tape very sticky .
2x power settings 2x circuits .....
( I'm hoping some one will correct me and )
( say things have got much better -mats/pads ? )

 

[Martin606]

Thanks for your replies

I have replaced the heater and still the RCD trips when calling for power on the thermostat.

Any other ideas anyone?

 

[SparkyChick]

You specifically state that when the 750w powers up, the RCD trips... does the same thing happen when the other unit powers up? Are they both on the same thermostat? If not, is it possible the wiring in the stat is wrong?

 

[static zap]

still the RCD trips ...
Any other ideas anyone?

Test the wiring , check neutral present and earth not loose ?
( IR testing if water / condensation is about )

 

[Martin606]

Thanks

Both on the same radial circuit.

I think I will have to double test the continuity of the circuit again. r1 rn and R2

Both heaters are tripping the RCD as I found out today so must be the wiring.

Cheers

Martin