Is grounding necessary if an RCD is installed on the water heater?
We can not decide to put a water heater, 2-way wiring, an RCD has already been installed on the water heater on the plug. Question: Is it necessary to carry out grounding or can it be connected?
Why can't you decide? In the normal case, grounding should be done. An additional potential equalization system, too. But half of the country works on two-wire wiring and everything is fine. An RCD on the plug is not bad, but it would be better if you put a normal, full-fledged RCD on the din rail for the outlet from which it will be powered.