I'm fitting a flush fit underfloor heating thermostat into a metal back box but noticed that there is no earth wire. I know that metal boxes have to be earthed but all the plastic boxes are for dry walls. Is there anything specific for this situation or should I just adapt a dry wall back box ?
You don't need an earth for separated extra low voltage (SELV) equipment, but for low voltage (230 volt) even if not connected an earth needs running, at one point pre-1966 you could have lights without an earth, but that changed in 1966.
So if mains voltage be it a plastic or metal back box there needs to be an earth.
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