Part P does not prevent anyone from doing any electrical work, provided they do it safely and, in the case of the (now very small) number of types of work that are 'notifiable', comply with the notification procedures. In the present context, the only relevant (or possibly relevant) things which could be notifiable are 'replacing a CU' and 'installing a new circuit'. Interpretation of both of those is subject to debate but, if one believes that the work doesn't come into either of those categories, then it could be done by anyone competent to do it safely (which might be you, for all I know) without any bureaucratic requirements.
Fair enough, but with most brands the price difference is far greater, and the DP ones much more difficult (or impossible) to find. I'm also not sure how many manufacturer's make single-width ones.
Yes - but as I said before, that's isolation,and that can be achieved with a Main Switch. AFAIAA, there is no requirement for a protective device to switch neutral.
I don't really understand that - it's 'all live pole'. Do you mean it doesn't switch/isolate the CPC (which would surely be non-compliant)?
I agree that is one advantage, but it is a pretty small one - particular with those makes for which the cost of DP RCBOs is high.
If that's true, it makes some sense, given the lack of space. I don't see it as a significant problem - if enough current is flowing in the neutral that one would want the overload part to trip, there surely would be the same current in the corresponding L - or, if you're going to postulate an incredibly unlikely cross-circuit fault, in the L of some other protective device?
JohnW2";p="3090350 said:
That's a good point - which seemingly makes it even less worthwhile to go to the effort and cost of including overload sensing on N as well as L (if, as you say, that's what the 2-module DP RCBOs do).
That may be a factor, but presumably another is that an RCD usually covers multiple circuit, so may have quite an appreciable 'background' L-N imbalance (due to L-E 'leaks in various loads) - hence making it more likely that 'spontaneous' nuisance trips will occur?
I agree - particularly if the suggestion is that there are both thermal and magnetic overload mechanisms on the neutral. ... and, as you say, pointless.
A neutral shorted to a solid ( ie very low impedance ) ground could be taking a large part of the installation's total neutral current from the neutral bus bar back to the sub station. A 1mm lighting cable could get quite hot if there was an electric heater shower in use.
Theoretically true, but to have a path, via earth, back to the transformer of considerably less impedance than the supplier's neutral conductor would surely be next-to-impossible - the earth electrode at the transformer would, alone, usually have a higher impedance than the neutral supply conductor. Indeed, even the 1mm² conductor of a lighting cable you postulate would probably have an impedance greater than that of the supply neutral! It's only really in the infamous, and very rare, case of a 'lost supply neutral' that such a scenario would seem realistic - and the chances of that situation arising at the same time as your very low impedance fault between a neutral and true earth would surely be of 'vanishingly small' probability.
Very much so!
I'm also old enough to remember when the water supply network was all metal, but I wouldn't know whether substations were 'bonded' to it!
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local
