RCD mystery

[crystal ball]

It has indeed but TTC thinks it can be tested after that

 

[ericmark]

With any wrench one can warp the casing, even with moulded breakers I have seen where 300 mm² cables are clearly putting a strain and how twin 150 mm² seem much better, but with larger devices it is easier to see and feel what strain is being exerted, tiny 25 mm² cables may not seem to be putting much strain on a device, but they often are, this is why we test after fitting.

However I am sure I am not the only one, who has had RCD's trip for what seems to be no reason, and they pass all the 6 tests, have changed the RCD just in case, and the problem has gone.

I returned to UK 1994 and while I was away two major changes, the ELCB-v was discontinued, and 16th edition had come out and tradesmen were being tested in their ability to read it. We have still not seen editions in Welsh so I suppose to test electricians can read English does make some sense. But I had worked away for nearly 14 years, and on return every waterproof main distribution unit (WMDU) had a RCD unit in it, often set 1A at 60 seconds, but there were RCD's feeding RCD's feeding RCD's each with shorter time and lower tripping current, but still a nail through the cable in a cabin could take out 4 RCD's.

Life as an electrician had changed, and in 1996 I came home and fitted RCD's to my own house after my son started to study to become a radio ham, and they have been tripping every so often since then, seems to be in batches, 3 weeks and tripped 10 times, then 2 years and nothing, and nothing changed, resetting one RCD has tripped the one next to it, and some times could only reset after turning off all the MCB's. This shouldn't happen, but it does, and after been fitted for 24 years I can be reasonable sure those trips were not due to faults.

I considered a number of methods to reduce tripping, there were some auto resetting, now not permitted with domestic, and there were some with built in monitors to show if there was a leakage before it tripped, seem to recall called X-Pole but with a name like that internet hunts seems to get the wrong items, or there was the use of RCBO instead of one RCD feeding many MCB's.

The regulations are a bit vague on how many RCD's are required, every installation shall be divided into circuits, as necessary, to take account of danger that may arise from the failure of a single circuit such as a lighting circuit and reduce the possibility of unwanted tripping of RCDs due to excessive protective conductor currents produced by equipment in normal operation, has been interpreted as meaning the lights and sockets in any room should not come from same RCD, in this house (not the one where fitted in 1996) since sockets split front/back and lights split up/down that means at least 4, but most house get away with 2, however the operative words are "get away with" in industry losing power costs a lot of money, loose power on a batching plant and you may find it will not restart full and you have to dump the batch and start again, so no one penny pinches and groups a whole load of MCB's on one RCD. But in the home, we don't seem to mind so much loosing power. So this house I could have saved around £200 by fitting 2 RCD's not that it would have really complied, but sure I could have "got away with it" but with 14 RCBO's I have not had any nuisance tripping, I have had a trip when water leaked but that is not nuisance tripping, and it only affected about 8 sockets, which I was not using anyway.

So either you split the house into more circuits, OK I know a circuit is "An assembly of electrical equipment supplied from the same origin and protected against over current by the same protective device(s)." but it does not actually say if only over current around the circuit, I would read that to be also over current to earth, and splitting a home into two circuits is really asking for problems. OK caravans and narrow boats only have one RCD, but they also have 12 volt lighting.

I watched the clueless electrician fitting a CU in my dad's house, not a meter in sight, and when the RCD tripped, he could not find the fault, because he had no test equipment, it was as simple as that, no insulation tester, no RCD tester and all sockets on one circuit, at that time RCD protection was not required except bathrooms and outside, so he fitted an isolator instead and run off into the hills never to be seen again.

Even with this house the electrician missed a borrowed neutral with lights, however that was an easy fix, back in 1994 RCD's were new to me, and we were all learning, today they are common place, and we all know or should know the regular faults. That includes attempts to "get away with" not splitting into enough circuits.

 

[SUNRAY]

However I am sure I am not the only one, who has had RCD's trip for what seems to be no reason, and they pass all the 6 tests, have changed the RCD just in case, and the problem has gone.

Been there more than once

 

[crystal ball]

I had an all RCBO CU in my house, one day four of them tripped at once, re set never happened again

 

[SUNRAY]

I had an all RCBO CU in my house, one day four of them tripped at once, re set never happened again

I've heard of this several times, there is nothing that springs to mind except some sort of spike in the supply but even that doesn't make sense.

 

[crystal ball]

An update I returned to site with the original RCD which had been sat in my garage CU with no problems, re fitted it and its been ok

 

[dannyboi2003]

BG stuff is utter rubbish so there's your answer, I've had so many issues with their RCBO's/RCD's which passed all tests fine but would constantly random trip for no reason, i even had to rip out and replace a BG full RCBO board that I had installed that was driving the client insane. Their tech support is dreadful who refused to acknowledge there was any issue with their products, as i result I don't use BG any more and never will again, I've had multiple failures of their socket outlets too. Hager are my go to brand now or Contactum if it's a budget job.