Use of isolators with showers, oven, and other fixed stuff.

[JohnW2]

My case is that the requirement for them should be engineered out at source (i.e. at the consumer unit). I'm not a fan of these split RCD units and don't see the logic of having fault protection across 5+ circuits:

Even if you don't feel that it goes far enough, the logic is surely clear enough - i.e. splitting the circuits across two RCDs is better than having them all protected by one RCD.

Your view is fair enough, but the extent to which it makes practical sense depends on how much inconvenience (and that includes consideration of how often it's likely to happen) results from operation of an RCD which is protecting several final circuits. I have personally lived with that situation for over 25 years, in an installation with a very large number of final circuits (and a good few RCDs) and can hardly remember the tiny number of occasions on which there has been any such 'inconvenience'. Indeed IIRC, I have never experienced an RCD operating 'in anger' because of an N-E fault (only when I've personally been responsible for N and E conductors touching on not-DP-isolated circuits!) - so I've always been able to immediately restore all the other circuits by switching off the MCB on the 'fault circuit'. Hence, at least for me, in practice having multiple circuits protected by single RCDs has not been a significant 'inconvenience' at all.

As I've said before, if you do the sums, yo'll find that the total cost of equipping all UK domestic installations with 'all RCBO' CUs would be truly astronomical - and one can't help but feel that the same enormous amount of money directed to other 'safety issues' (not necessarily even electrical) could result in considerably greater reduction in 'loss of life and limb' etc.

IMHO the isolators can also encourage the tradesman to be lazy about their taught 'safe isolation' procedures ...

I don't think that's really a designer's problem - and, in any event, there are always going to be ways in which tradesmen can, and will, be 'lazy about what they've been taught'.

... and present another link in the chain of terminals that can cause fault.

Theoretically correct, but I really think that's going a bit far! If we designed installations so as to minimise the numbers of connections at terminals, installations would be very different from what we are used to - for a start, circuits supplying more than one socket or light would presumably be banned?

Kind Regards, John

 

[JohnW2]

Imagine what it was like when there was only 1 rcd prior to the cu.

Quite so. I, for one, lived with such a situation for a fair time (without any problems). Countless installations out there are still like that and, indeed, there are still plenty with no RCDs at all!

Furthermore, as I frequently say, I continue to suspect that we tend to seriously over-estimate what has actually been achieved by the introduction (at great total cost) of RCDs!

Kind Regards, John