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Weird RCD trip

Still trying to track down our RCD trips ...

Why would switching on the lights in the detached garage trip the RCD, given that the lights aren't on the RCD? It's a split CU.

Reply to
Huge
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lights wired to wrong neutral bar?

neutral to earth short on lighting circuit?

water/gunge/dead spiders in a junction box?

lighting and power circuit neutrals joined somewhere?

Reply to
Andy Burns

En el artículo , Andy Burns escribió:

"spiky" lighting (e.g. large number of flouros) tipping marginal/sensitive RCD over the edge?

RCD replaced?

Huge, wonder if you've considered trying a 100mA RCD as a temporary measure? Is the nuisance tripping getting worse?

Reply to
Mike Tomlinson

lighting not connected to the RCD? I'm as puzzled as OP.

What I did was to replace the RCDs with RCBOs. That way only the affected circuit gets cut off.

Reply to
Scott

I'm slowly coming to suspect that the power & lighting circuits are indeed linked.

The RCD only covers the power circuits. The lighting shouldn't affect it at all.

Not yet.

The thought had crossed my mind. :o)

It comes and goes. It tripped three times on Xmas Eve (great timing, eh?) but not again until yesterday. It's now tripped 4 times in the last 2 days. I'm keeping a log, but there doesn't seem to be any correlation between anything (especially rain!) and the number of trips.

Reply to
Huge

Oh, and switching on the kitchen lights tripped it a couple of hours ago, as well.

Sparks (x2) says not.

The lighting isn't on the RCD ...

I've checked all the outside wiring and cleaned out all the cack.

Could well be.

Reply to
Huge

Is that every time you turn the lights on or just a one off?

Reply to
ARW

What happens if you disconnect the neutral and live of the affected circuit at the CU, and then test for continuity to a still connected neutral?

Reply to
John Rumm

Intermittent. Maybe one time in 20?

Reply to
Huge

Dunno. Haven't girded my loins sufficiently to open the CU. Although I have peered over the shoulder of both sparks. I think I'm getting sufficiently annoyed to do it, though.

Reply to
Huge

A neutral to earth fault anywhere on the installation (whether protected or not) can cause this. A borrowed neutral (usually on two way switched lights? Similarly a proliferation of equipment with noise filters on the mains can give sufficient standing leakage that any transient spike can trip the RCD.

Reply to
Peter Parry

Thanks.

Reply to
Huge

A good test of your RCD then.

Reply to
Andrew

I have this strange feeling of deja vu...

Reply to
Jeff Layman

IIRC you have a lift (and I assume sockets) in the garage. Are these on the same RCD which trips? If so, how easy would it be to disconnect them completely (ie all 3 cables) so as to eliminate the possibility of leakage across the lighting circuit and the power circuit there?

Reply to
Robin

Cheers!

Reply to
Huge

Well done for the memory, but no, I have both a garage (mostly used as a shed) and a workshop. The lift is in the workshop.

Yes.

The workshop has its own RCD, downstream of the one that's tripping, presently switched off in an attempt to narrow down where this is happening. Rewiring the workshop is on the list, once the tuits become available.

The wiring in this house is a mess.

Reply to
Huge

I've had similar twice in the recent past. First time I fitted an induction hob on a RCD protected circuit. Absolutely no faults at all on the circuit when tested. Occasionally, when turning on the hob, the RCD would trip. So I changed it to a non-rcd protected circuit breaker. And it carried on tripping the RCD ocasionally. I changed the RCD, put the hob back on the RCD protected side, and all was well again. Clearly there was a spike that occured when the hob was turned on, but why did it trip the RCD when it was on the non-rcd side? Well, the neutrals are conneted at the main switch, somehow a back feed was causing trouble for the RCD, so it tripped.

And another time,though these were on the RCD side, when SON lights were turned off, they tripped the RCD. This was traced to a faulty double pole switch (after much head scratching) which would disconnect the Live slightly faster than the neutral, and with the SON lights coils with some charge in them still, the RCD was sensing an imbalance and tripped. Making the switch a single pole on the live only fixed it.

In your case, I'd be looking to change the RCD first, they are cheap, and/ or having a look to see if your lighting is deteriorating, and giving an higher than usual earth leakage.

Reply to
Alan

So you can forget the borrowed neutral suggestion that anyone makes. That would trip the RCD every time.

You have a NE short on the RCD side of the CU.

The garage lights are simply passing some current down both neutral and earth due to the NE short.

Reply to
ARW

I assume the old wiring is inherited, ie you only have what has been discovered to go on.

I find these new fangled protection systems very sensitive if used with any older wireing myself. Even condensation in a box somewhere seems to trip them. I know they are supposed to be fast and thus safer, but sometimes I do wonder if we are not expecting things to be better than they may be after some years in situ. My own house is old fashionse, and thus far has killed nobody despite the lack of electronic protection other than a circuit breaker though there is an rcd for outdoors and sheds.

Brian

Reply to
Brian Gaff

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