I have been told the following: "When I install my new consumer unit, I should use a split-load CU, where the lighting circuits can be protected by a 'slow' RCD, and the power circuits can be protected by a 'fast' RCD"
Questions:
1) I assume the difference between 'fast' and 'slow' is the rated trip current: 30mA being 'fast' and 100mA being 'slow', but why has my 'advisor' recommended different ratings of RCD for lighting & power circuits?
2) What's the reasoning behind a split-load CU? What's to stop me protecting all circuits with one RCD on the incoming mains?
3) My leccy supply comes from overhead cables. Does this dictate what rating of RCD I should use, and why?
4) My existing CU has an 80A/30mA RCD but no separate mains switch. I thought RCDs were double pole, so do I need both?
Questions:
1) I assume the difference between 'fast' and 'slow' is the rated trip current: 30mA being 'fast' and 100mA being 'slow', but why has my 'advisor' recommended different ratings of RCD for lighting & power circuits?
2) What's the reasoning behind a split-load CU? What's to stop me protecting all circuits with one RCD on the incoming mains?
3) My leccy supply comes from overhead cables. Does this dictate what rating of RCD I should use, and why?
4) My existing CU has an 80A/30mA RCD but no separate mains switch. I thought RCDs were double pole, so do I need both?