Installing RCBO Query
- Thread starter veedee
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If you feel such is how it should be, you are obviously free to post a comment about testing on Page 1 of every thread in which an OP is proposing to do anything to an electrical installation.
It is, indeed,the case that, in theory, any electrical work should be followed by some 'testing', but the extent to which it would/could be helpful and/or important will depend upon the situation. In terms of this thread, I'm not sure what extent of 'testing' you were contemplating but,unless the OP failed to tighten the screws satisfactorily when installing the RCBOs, the results of any/all testing would presumably be exactly the same as if he had done no work (and hence no reason for testing would have existed),wouldn't they?
Well, obviously those circuits - but what 'tests'- and,as I implied,more to the point, what tests the results of which could conceivably alter as a result of changing MCBs to RCBOs?
About the only relevant test after such a change would be to test the residual current functionality of the new RCBO, but very few DIYers are going to have the ability to do that. Beyond that, any testing would really only be done, in almost a 'routine'sense,simply because some work has been done on the circuit - but it's as likely that that 'almost routine' testing of any other circuits in the installation would detect problems.
People tend to produce knee-jerk comments about testing of DIY work - in the real world, useful advice to DIYers would relate to which tests are important, and why - and probably should remain realistic in terms of what testing a DIYer is likely to be able to undertake since, otherwise, we might as well just tell people not to do DIY electrical work.
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I'll add that the most useful test result would be to find any shared neutral. The easiest way to find that may be to temporarily move one of the existing lighting MCB's and its neutral over to the RCD section to establish if anything trips.
Yes, and we've discussed that at length - and it's clearly an investigation that should be undertaken before the lighting circuits are moved to RCBOs.
However, I wouldn't really call that Investigation 'testing 'in the usual sense, and I think it very likely that the 'testing' which markyd1 referred to would (as it always is when people raise the issue of the testing {or not} of DIY electrical work) testing done after the work had been undertaken - by which time one would be well aware of the existence of an issue (even if one didn't realise that it was due to a 'borrowed neutral') without having to do any 'testing'
I think that what we are saying is that some rudimentary testing before the event can often prevent surprises after the consumer unit is changed (and help to reduce some nasty surprises when working on a "dead" circuit)
Are you now talking about something other than the possibility of 'borrowed neutrals' and the desirability of 'checking' for this before doing things that could result in circuits with borrowed neutrals ending up on different RCDs/RCBOs (a topic we did to death earlier in this thread).
If you are (talking about something different) what 'rudimentary testing' did you have in mind which could have a bearing on (be relevant to) the OP putting his two lighting circuits onto separate RCBOs?
Kind Regards, John
No John, I am talking about the "Borrowed N scenario" being not too difficult to make a rudimentary check on in the very first instance as a guide only. Not totally conclusive but might well alert the DIYer to the possibility of such.
Example - Put all lights on, power down, disconnect L on one circuit (such as remove fuse or trip breaker), power up then see which lights remain on. Then repeat the exercise by removing N.
Then repeat the exercise with second and subsequent circuits.
this is not totally fool proof (such as a "borrowed" L for bathroom fan timer overrun) but is a simple means of finding which circuits have the L & N in apparent proper order.
In its simplest form it would show the classic borrowed N for stairway lighting because that lamp would not light with L or N from different circuits disconnected or it might cause strange lighting effects with filament lamps at least.
Like I said, not foolproof but as a first line of defence is a simple test method that could be carried out by a DIYer with minimum fuss.
LEDs rather than filament lighting could beggar that up but at least it gives one another chance to be alert to something not quite right in the first instance.
Obviously, proper testing with proper test gear by experienced persons would be the ideal but we do not live in an ideal world so in the real world every chance of gaining a clue for minimal effort has its merits, even if that is "Hmm needs some more tests to find out what we have before us".
Straightforward wiring on basic power circuits has a tendency to be more basic in a lot of cases. Lighting circuits though, although some do then a lot do not, both the borrowed N and alternative switching arrangements and further alternative differing switching arrangements used throughout the same installation can throw folk off track, not just the DIYer but experienced trades too.
In my experience, the number of "surprises" that outfox many, are more often than not (but not exclusively) lighting circuits.
If we take three different basic methods of wiring lighting and call the Loop In/Looping In/Joint Box then consider hybrids of 2 or three of those methods then, perhaps, throw in the borrowed N into the mix too, it can cause a lot of head scratching at times.
The number of times I have heard a pro remark "Well I never thought anybody would have done that!" once the source of the problem is revealed and rectified, is not as rare as we`d hope it to be. I can give a classic example of that remark.
I that case, we did that discussion to death a few pages back, and suggested various ways in which one could undertake such a 'check'.
However, again, although I may be wrong, I don't think that's the sort of 'testing' that markd1 was referring to.
OK Fair point (and we all know that I am capable of rambling on/going off at a tangent) it`s a fair cop m`lud!
Wow, never expected to find this thread on the first page
1x light and 1x Ring MCB's were swapped for RCBO's about a week ago. Easy work.
Was i supposed to do some sort of test prior/ after installation?
Or can i call this a shut case?
1x light and 1x Ring MCB's were swapped for RCBO's about a week ago. Easy work.
Was i supposed to do some sort of test prior/ after installation?
Or can i call this a shut case?
Yes you were supposed to test
I asked whether JW was muddying the waters.. Was told to just crack on with original plan of changing MCB's for RCBO's. So did that.
Okay, no problem.. Will re-read the thread and do the recommended test.
After that, I am closing this case.
Fair enough. That's essentially what I suggested.
That might not be as easy as you think since, despite my having asked, no-one has yet indicated exactly what tests they would like you to do.
Some people knee-jerk with comments about the (very common) absence of testing' of DIY electrical work, given that, strictly speaking,it should be done after any electrical work. However a fair bit of the 'testing' that would (should) be done routinely by elections could not be done by most DIYers - so, as I said, the 'only solution' to that would be to tell most DIYers not to do electrical work (which no doubt is the view of some people).
Kind Regards, John
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