Intermittent rcd trip on lighting circuit when under load

[CraigJTD]

Hello there i wonder if anyone could offer any advice on a problem I am having:

Although not a qualified electrician, I recently swapped out the old Wylex re-wireable fuse board in my house and replaced it with a split load dual rcd board. Before anyone tells me off, I am not a complete novice and trained as an electrician for three years before dropping out with one month left to qualify (a long story).

Anyway since the recent switch I have been having problems with the downstairs lighting circuit. One particular circuit, the wall lights downstairs, trips the RCD as soon as it is turned on. Once the lights are turned off the RCD will reset no problem.

As I am little rusty on the testing side of things I drafted in one of the lads who is a qualified electrician. He has since been around to carry out some tests, to check for borrowed nuetrals, L-E faults, L - N Faults etc had has come up with a blank. If it is of any help it was a Metrell all in one tester that he used.

We have tried removing all the bulbs and just putting one in each fitting in turn (there are 4) to try narrow it down to one particular fitting but it trips on every one.
This was two weeks ago, my mate is very busy at present with getting his house sorted for the imminenant arrival of his first baby so he is hard to pin down.
In the meantime I just thought I would do some digging to see if I could come up with anything.
Since taking all the bulbs out of said cicuit I have had 2 subsequent trips, which is now making me lean towards thinking that it may be realted to something other.

Any ideas/suggestions as to cause or tests that would help identify would be greatly appreciated, I am beginning to wish I had just left the old board in!

Thanks in adavance

Craig

 

[SimpleSimon]

So these subsequent trips are they still immediately when you hit the wall lights?
I would be taking the whole fitting off each of them, that way you can illiminate if its the whole fitting or the circuit.
I would hazard a guess that the walk lights are looped in between the four. May be worth splitting the cables between the middle two lights so you then can break it down further.
Any recent pictures gne up between the lights with a nail and picture hook?

Sent from my GT-I9100 using Tapatalk

 

[GT1]

Have you got the lighting neutral on the correct neutral connector inside the board ?
ie to the correct RCD. ?
Easy mistake to make if it's not neat and/or crowded. !

 

[CraigJTD]

SimpleSimon:

No the subsequent trips have just been random, they may be unrelated I don't know.
The wall lights do not trip the rcd if i switch them on or off now that I have removed the bulbs which I find strange.
I will have a look at taking the other three fittings off (i have already removed one), I really cant see this making any difference though as any fault to earth or otherwise should have shown up on the insulation test??
The lights aren't looped, they are switched back to a maintenance free Jbox under the newly laid laminate flooring and then spur off from the Jbox to each individual fitting. I am really hoping I don't need to get back to the Jbox as it will be a right biaaatch!
Nope no pictures gone up!

GT1
Iam 99% certain that I didnt cross the nuetrals, I like to think I am very thorough and organised so I would be very surprised, plus my friend has (I think!) done an insulation test between the two Neutral bars and all was ok.

Thanks both for your replies is there anything else you/anyone can suggest.

 

[topquark]

May be down to a loose neutral (that can often cause faults to be intermittent, has been found sometimes before the circuit origin at the OCPD as well ie at both the service head and main/rcd neutral).

 

[CraigJTD]

Just looking at what I have called this thread and the title is a bit misleading, sorry!

The main fault is not intermittent, it trips without fail when the wall lights are switched on (as long as the/one bulb/s are in).

I have checked all terminals within the CU, will check connection tightness at fittings - thanks topquark

 

[topquark]

If it happens consistently when the switch is operated then de energise and islolate the circuit completely then IR test again with the switch closed (it may have only been done with switch open before). Or possibly only done on one set of two way switching (only tested one of the strappers).

 

[vernam616]

A borrowed neutral from a socket below and just so happens that socket is on the other side of the DB??

Highly unheard of now, however back in the days of old wylex rewireables......... anything went !

 

[CraigJTD]

Ok now I am really confused....

I have taken all fittings off the wall and set about trying to re-fit them one by one. Only problem is now they won't switch on at all!?! And the RCD isn't tripping.
I have neon screwdriver that is showing a current running on both the live and neutral side of each fitting but the bulbs are not lighting??? How can this be??

I have also tried rigging a spare pendant fitting that I had laying about with a bulb that I know works. That won't light either??

Am I losing the plot or does someone have an explanation?

 

[vernam616]

Call an electrician

To use one of the neon screwdrivers as a test instrument is just going to make the whole situation "Fail"

 

[hughesy]

i would ditch the neon driver and get some test lamps. as topquark said re do i.r test with switch open and closed then the fault will show up, sounds like you might need to get to that joint box if each light is individually wired from it and now they dont work

 

[hughesy]

if it trips when any one of the lights is on then the fault will be from the joint box back to where its fed from other wise if it was aftrer the jb only one light would trip the rcd as ther individually wired from the joint box.

 

[CraigJTD]

Thanks for the advice guys. Seems very strange that the lights were tripping the RCD before i took them off the wall but now they aren't although they won't come on. Also that the wall lights worked fine on the old re-wireable board ??

Anyway Vernam616 my best mate is an electrician, he is just a little busy for the next week or so, so I was trying to see if there is anything I could do in the meantime to resolve it. I can't be affording the rates you boys charge!

I think I will just wait till his missus spits the little one out and then get him back with his testing gear and suggest he tries what others have suggested re open/close IR test etc

Thanks for the help suggestions

 

[chelwood]

Why would you want wall lights on an rcd