lighting problem

BMelectrics · Jul 11, 2012

Hey Guys,

Picture this,

15 way board,

6 circuits on 1st RCD are fine,

then there are 6 circuits on the 2nd RCD, and the lighting circuit is coming off of the main switch (6a breaker)

The lighting circuit: i switch on the first 3 lights in the circuit and all is fine, but there is one light, that when switched on TRIPS THE 2ND RCD.

the light (since not being on the RCD) stays on, but acts like a strobe light!!

I went up into the attic and checked the joint box and tightened the neutrals, light stopped flickering, "ah great" I thought.

Went back down to flick the 2nd RCD on but it wouldnt come on, kept tripping!

bulb was fine ans seems to be the only light on the circuit that trips the 2nd RCD.

Strange, it was late on today and never got a chance to get into it, one for tomorrow,

what do you guys think???, ****ty neutral to the specific light??? it was strobing, but now isnt, but is tripping an RCD that it is not on!! neutral cable in Board is in correct neutral bar!

Thanks!!

topquark · Jul 11, 2012

Is this a high integrity board with 3 neutral bars?

BMelectrics · Jul 11, 2012

yup 3 neutral bars!!!

jdd · Jul 11, 2012

Neutral is in wrong place at con unit mate or some numpty has joined neutrals together at a jbox.

BMelectrics · Jul 11, 2012

there are a bunch of neutrals joined in the junction box, why is it only the one light from that circuit that trips the 2nd RCD??? what was the deal with the strobing light??

jdd · Jul 11, 2012

Not sure mate, could be something daft like a breakdown in insulation I guess. I'd separate those neutrals first. Also perform an insulation test on that lighting circuit with switches open and closed.

- - - Updated - - -

Was the strobing light CFL or LED by any chance?

topquark · Jul 11, 2012

Distance between the lighting MCB and second RCD would suggest that's it's probably not an electromagnetic effect on the RCD.

First thing is trace the neutral runs (if you haven't already). Is it possible that you've picked up the wrong neutral on the two way lighting circuit (upstairs/downstairs) for example.

What is the type of light fitting/lamp that exhibits the strobing effect?

Also worth checking the main RCD neutrals in the CU for tightness. Then ramp the rcd to see what it's tripping at. Also worth swapping the RCD unit (exchange with the other one if you don't have a spare) in case it's faulty.

Des 56 · Jul 11, 2012

What lamp type is in the problem light
Will the rest of circuit operate when the rcd has tripped

Farmelectrics · Jul 11, 2012

Poor insulation or borrowed nuetrals ir tests and clamp meter on neutrals would solve this problem one thinks

BMelectrics · Jul 11, 2012

it was low energy bulbs, i just had a thought,

On the 2nd RCD there is another lighting circuit doing the upstairs.

The one that is tripping is the downstairs light, but it does one of the lights that is upstairs!

maybe a shared neutral!!

the only reason i had this circuit off the RCD was because i ran out of space and had to put the downstairs lighting circuit on the main switch side!

I think I will temporarily take the upstairs light off of the 2ND RCD and onto the main switch side, and suggest a rewire to the customer in order to get the lights back on RCD protection!