Thanks mikilianis. I understood it to be a safety device. As an enginer i believe that everything must have a purpose and I need to understadn its purpose first before I believe anybody claiming that it has not purpose and can simply be ommited. But I am not so sure about the lighting. I rather have no light than not triggering the E/L when accidentally touching a live light circuit wire. Anyway, so far that did not happen to often. I am not a great competancy of electricity and stay away from things which are beyond basic connections.

Something else: I was quoted 5 hours labour (excl materials) to replace a main breaker and put a surge arrestor next to it. Am I right in saying that its a matter of making a few cable connections at the board which - lets be generous - should not take more than an hour maybe?