I made a mistake, it is no good saying it was what everyone did at that time, over the years it has been shown I made a mistake, my son will be correcting it for me, sons do that they look after their dads, but I thought 2 RCD's were enough, hind sight is easy, I should have fitted 100 mA RCD's with 40 mS tripping times not delayed which at the time fitted was within the regulations, I have had batches of RCD tripping now for 25 years, but to be fair when I fitted the RCD's you could not buy single width RCBO's they were all 2 pole and rather expensive, neither could I have bought a high integrity consumer unit, not even sure when I fitted them if you could by a consumer unit, think still called distribution units then don't think the type testing had come in, it was early 90's when working at building of Sizewell 'B' my son decided to become a radio ham and I wanted to protect him as he started to play with electricity.
Today things have changed, everyone fits 30 mA RCD's both stand alone and combined with the MCB and the availability of boards and the price of RCBO's is no longer a problem, even in 2001 when BS7671:2001 came out, still called residual current device the word RCD was not used in the regs then, and only required for "installations and locations of increased shock risk" listed in Part 6 as it was then. When I fitted the RCD's I could have taken a non protected supply to my freezer, that would have saved me a few hundred pounds when the power did trip while away from house, I had considered fitting an auto resetting type, before they were not permitted, but never got round to it.
I made an error of judgement, and have paid for it with loss of food and many walks into the garage to reset power over the years, but in my defence when I fitted them, very few houses had them fitted, and only internet like way to pass on info was the bulletin boards and Clive on packet radio, today the electrician knows the problems and should explain them to customer and as say if after that the customer wants only two RCD's then any trips is down to the customer, but so often I talk or read about where the owner had no idea of the problems, he had only had the safety aspects explained to him.
And for what ever reason, he is left with an installation which trips on a regular basis, and even then is told it is his faulty appliances which in some cases it is, but often it is simply a build up of many leaks which together cause the problem.
So to be fair son has moved from 2 up 2 down where 2 RCD's proved ample. But in this house with 13 rooms (including toilet/shower so some very small) 2 RCD's would not be enough, when I moved in there was one RCD, which covered 2 rooms, how did any electrician consider it was right to fit a new consumer unit when the RCD covered half the bottom floor of a three story house, when the next floor was also a ground floor at front of house and likely to have items used in the garden plugged in, in fact I have just recharged the battery in wife's car from a socket in her bedroom on top floor, house built on the side of a hill.
When I moved in most of the house was protected by re-wireable fuses in between the false ceiling and original ceiling with a 9 inch square hole in false ceiling you could just get your hand into to change them. But since we have no idea what the electrician said to owners when he did the job, can't really blame the electrician.
But with 14 circuits, it is to my mind plain that 2 RCD's are not enough, also no good way to split so lights in every room are on different RCD to sockets. Lights split up/down sockets front/back. So all sockets would need to be on one RCD and all lights on another, so 10 circuits on one RCD, there was to my mind no option but fit all RCBO, it also makes the CU 4 slots shorter.
So when I found next door on two RCD's you ask what was the electrician thinking. How can anyone sign to say they have designed a system for a house that size with just 2 RCD's?
It is obviously literally true that CPC current does not cause an RCD trip. It is also true that if piece(s) of equipment result in L-'E' leakage ("not due to a fault"), then some of that current could pass to earth via a 'parallel path' (if one existed - e.g. if a Class I item were used outdoors with its exposed-c-p in contact with wet soil), rather than all going through the CPC.
