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

 

[Octopus]

Are you sure its got 2 main switches?

 

[GarryJ]

Well there is main 100A 2 pole main switch with busbar attached feeding mcb's (one of these the affected lighting circuit) Then from bottom of this main switch as well as busbar is flexi tail feeding top of RCD main switch feeding its circuits. There is 2 neutral bars - one for standard mcb side and one which has all outgoing rcd circuits neutrals. (Supply neutral to top of RCD main switch is taken from mcb neutral bar

Hope that makes sense ha

 

[Octopus]

So you have a main switch and a RCD.

 

[GarryJ]

Yes and mirror light which is definitely causing the problem is fed from main switch side not RCD

 

[telectrix]

has this fault just cropped up, or is it coincident with fitting the silly mirror?

 

[walsh builders]

Have they pinched a live from the lighting circuit and a neutral from an RCD protected circuit when they've fit this mirror??

Does sound a bit weird though, you'd expect it to trip every time.

 

[GarryJ]

According to the customer the fault started once mirror was fitted a few months ago but I looked at it a few weeks ago and said it couldn't be the mirror as it was fed from lighting circuit that had nothing to do with RCD side and to keep an eye on it and try and keep record what is on when it trips to identify the intermittent problem. However I was back the other night for an hour and if I turn on mirror enough times it will definitely trip the RCD

 

[Octopus]

I would start by isolating the mirror and Iring the circuit

 

[GarryJ]

Have they pinched a live from the lighting circuit and a neutral from an RCD protected circuit when they've fit this mirror??

Does sound a bit weird though, you'd expect it to trip every time.

Not sure mate going back to it beginning of the week to start testing but as you said I would have expected it every time. To my knowledge their was a mirror light there before this one so supply is not new which is making me think the LED aspect of it may be causing problems but it is still confusing me how it can trip the RCD when its not protected by it?

 

[cprfenom]

Wouldn't isolating the mirror from supply between visits be a solution if you're convinced its the mirror?

 

[cprfenom]

Maybe the RCD and mirror were having an affair and its rebelling against the owners for replacing her?

 

[dcelectrical]

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?

 

[telectrix]

send an ugly woman round. mirror cracks - end of problem.

 

[dcelectrical]

awww, tel - ugly women need love too.