Wiring problem on room thermostat?

[Ihatemondays]

Hi, my cousin has had a new pump fitted to her boiler. There was no other work carried out. The fitter said that he got an electric shock from the 'earth' from the room thermostat (twin and earth cable)

I investigated, and found that there was 240 volts in both the brown and the green/yellow cable from the thermostat. I take it that is not normal, but am unsure as to how the thermostat works - is it just an electric switch controlled by the dial? If so, therre should no reason for 240 volts in the earth cable.

Can anyone confirm my opinion? Any suggestions? Is the thermostat faulty?

The heating works OK, and so does the water. Thanks guys!

*Also posted on 'Plumbing and heating section*

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[slippyr4]

You need to look inside the thermostat itself (after turning off the CH controls power) and see what the earth core is connected to.

Sometimes ***** installers use the earth core for switched live, when there is only 2core+earth cable - newer thermostats with anticipators need live, neutral and switched live.

It's dangerous, against the regs, and possibly illegal to do this. If it's the case then the best bet would be to change the cable, but at the very least to brown sleeve the earth core to show it's not really an earth at all.

 

[Ihatemondays]

Thanks, Slippy! I reckon it might be the earth is used as a live, as you say - but will check it out!
Thanks again!