Just bought a new shower heater, and the electrician is installing it tomorrow. I'm going to ask him to reverse the wiring to the consumer unit, so the black wire is live, but if he refuses, will the ELCB still work?

Should I just wire it up reversed, so the shower unit is black wire live, and leave the rest of the house grey wire live?

At least I know the earth is going to work, even if I have to hammer it in myself!

Thanks for any advice.

Yes, your RCD will work just fine with L and N reversed, that said you should really get it sorted.

Yes, your RCD will work just fine with L and N reversed, that said you should really get it sorted.

Thanks Crossy.

Yes, I'll do my best to get it sorted.

Well, I was wrong about the wires coming into the house being reversed. While the circuit box cover was off I was able to ascertain with the trusty neon screwdriver that the L is indeed the black wire and grey is N. So somewhere between consumer unit and the plug boxes something has gone awry. Beyond my resources to fix, so they will stay that way till the house owner decides to do something about it.

However, as the wire from consumer unit to my new shower is a new install, and goes no where else, the power to the shower goes via black ( L ) and grey ( N ) with black "hot".