Rcd tripping strange fault

[GarryJ]

Evening all.

Popped in to see a job today -

Customer has a split board - 5 or 6 breakers fed from RCD 30mA main switch ( feeding sockets, shower etc as expected) and 5 or 6 circuits fed from standard 60898 mcb's off the main switch side ( lights, alarm etc again as expected)

The fault is - there is a LED mirror light which is fed from the mains lighting joint box which is in turn protected by 6A mcb in consumer unit, however maybe around 1 in ten times when turning on the mirror light it trips the RCD? Now this circuit is not even through the RCD and never happens with any other lights on the circuit and if the mirror is on it will not trip its only when turning it on (Its one where you swipe your hand down the infra red sensor at the right hand side).

I am going back with a view to testing the RCD to make sure it is not too sensitive at x1/2 etc and also plan to disconnect the lighting circuit and actually put it on the RCD side of the consumer unit to rule out any mixed neutrals etc but if this was the problem I would have expected it to do with other lights and every time it was turned on?

Are LED's still a dark area with causing tripping?
Anyone ever has similar/ same problem?

Thnaks in advance

 

[cprfenom]

Tell that to all the poor mirrors

 

[telectrix]

awww, tel - ugly women need love too.

yes, but only in the dark. :49:

 

[GarryJ]

its pure conjecture but I am thinking that the cabinet is introducing stray voltages and somehow this is getting to the copper pipework and its tripping the heating/hot water related circuitry and it doesn't trip every time because it takes a while for the stray current to build up enough ampies to trip the RCD. however what is not conjecture is that those LED hand operated lights are a bloody nightmare and my experience of them is that the electrical components are the cheapest of the cheap crap. is the cabinet metal?

Yes cabinet is metal

Im heading back next week and will start testing - I am going to put this circuit on RCD side to rule out mixed neutral problem etc then see what happens

Thanks for your help

 

[dcelectrical]

My brain is now thinking that the cabinet is earthed and that the lighting circuit is not earthed so well and those little electrons are wiggling their way down the easiest path to earth as a test I would fly lead the cabinet to a decent earth and see what happens, but that's just me and im a bit strange!

 

[Rs electrical]

Try a new rcd you never know it might not like the led drive . I had a washing machine that kept tripping the rcd tested the hole install couldn't find nothing wrong so blamed it on the washer customer got it tested and was told it was fine so went back and changed the RCD fixed the problem. There are different types of RCD A , B AB . Also had a shower that would trip the other rcd on a daul board found out that a microwave had slight earth leakage which would trip the rcd when a high current would flow. So make sure everything is unplugged or isolated on the rcd when switching the light on.

 

[davesparks]

If i've understood this correctly you have a circuit on the non-rcd side of a board apparently causing the RCD to trip?

Have you ruled out the obvious multiple N-E fault scenario by carrying out insulation resistance testing?
What about measuring the imbalance in the tails with a leakage clamp meter and testing the RCD for correct operation?

Or alternatively you could just carry on with moving circuits around in the board, replace the RCD, speculate about the cause and maybe even just bypass the RCD and call it fixed. Are you charging the customer by the hour for this faffing around guessing and not carrying out the basic logical tests?

 

[marc8]

Hi Garryj
from what you are describing someone has pinched a nuetral from the RCD side of the board, you may have more than one junction box somewhere under floor in loft, at time when you turned on mirror light did you have any other lights on in house or any other circuits?
one quick way to test would be to ditch the neutrals from the RCD side of the board with the Circuit breakers off on the RCD side, check see if all the lights in the house still work, could then also check whilst they are still disconnected if you have any voltage on the nuetral connections you have removed ( make the nuetral into a choc strip so they touch each other & make easier to check voltage) whilst checking the voltage try all the light switches through out each sequence on & off.
Good luck

 

[stevethesparks]

Is this mirror in a special location, ie bathroom / shower room?

 

[Deleted member 72666]

If i've understood this correctly you have a circuit on the non-rcd side of a board apparently causing the RCD to trip?

Have you ruled out the obvious multiple N-E fault scenario by carrying out insulation resistance testing?
What about measuring the imbalance in the tails with a leakage clamp meter and testing the RCD for correct operation?

Or alternatively you could just carry on with moving circuits around in the board, replace the RCD, speculate about the cause and maybe even just bypass the RCD and call it fixed. Are you charging the customer by the hour for this faffing around guessing and not carrying out the basic logical tests?

This is what an electrician would do.

 

[walsh builders]

Did you find out what the fault was Garry?