RCD tripping

Falcon L

Hi All,

Newish installation, 2 years old. Rural location.

The RCD trips out for no apparent reason. Even with nothing plugged in. We can go for 6 months with no interruptions and then it will trip every 5 minutes, then not trip for a month. Two sheds have their own supply and the lights flicker when the house RCD trips. The shed RCD never trips.

Question is: could it be power surges causing the trips?

Thanks in advance.

Delta Lima

I would have thought it was unlikely that a power surge should cause it to trip.

Have you got an immersion heater? That's a possible cause. Are you sure everything is unplugged when it starts to trip? I'm thinking of dishwasher or washing machine etc.

I once came across a wire that was nicked by a long faceplate screw behind a socket.

If it starts to trip regularly again, switch off all the MCBs on the RCD circuit. (That would be sockets or any immersion heater. ) Turn back on the RCD and start putting up the individual MCBs in turn, to see if the RCD will trip on a particular circuit.

Be sure the power is off if you decide to check behind sockets. That would be a last resort check.

Falcon L

Thanks for the reply.

No immersion heater. The RCD tripped while we were away during the summer. Everything was unplugged and I mean everything (OCD wife:D).

The RCD can be reset immediately and it won't trip again for anything from 5 minutes to 6 months or more. :eek: The sheds have their own unit which never trips.

If I'm working in one of the sheds I can tell when the power has tripped in the house as the portable phone beeps to indicate loss of signal from the base, and it seems to happen at the same time as the shed lights flicker.

If not a surge, is there some other network condition that might cause this?

Delta Lima

Have you any other circuits not on plugs, that might be wired through the RCD? Oil Burner? Bathroom lights?

Bruthal

Intermittent trips are often caused by neutral earth shorts. When that happens, loads on circuits other than the one that has the fault can cause RCD trips. RCD circuits which go outside the house are another one that can cause problems with varying water ingress to sockets or lights.

But there are lots of potential causes of RCD trips.

meercat

have you a well or septic tank

its best if the pump is on a dedicated rcbo

Falcon L

So, nothing external could cause this. I think it's time to call the electrician that did the installation and ask him why it's happening.

Thanks for the info guys.

Colser

I know you said rural area but have you ever asked your nearest neighbour if they are having similar problems? Id be thinking this is an external problem.

Falcon L

Colser wrote: »

I know you said rural area but have you ever asked your nearest neighbour if they are having similar problems? Id be thinking this is an external problem.

Immediate neighbours don't have any problems. My sheds have no problems. Just the house RCD.

What kind of external problem do you think might cause this? The fact that the shed lights flicker when the house trips makes me think it's something in the supply causing the trip. Not being a sparks, I could be way off the mark though.

Bruthal

Anything wired on an rcd circuit internal or external can trip them. External circuits are more at risk of water getting in. External lights etc that are on the rcd are one example.

RCDs themselves can be faulty too.

One good way to find a non obvious problem is switching off every RCD controlled MCB and disconnecting all neutral from the RCD neutral bar, and testing each to the earth bar.

Another method is to split the RCD circuits over 2 RCDs.

woody1

just spent an hour figuring out that the pump in the septic tank was tripping mine.. have you a pump or any electrics outside..

Falcon L

OK, had the sparks here today. No faults on any of the circuits connected through the RCD. No wiring issues (misplaced neutrals??). Plugged everything in that we would ever use... no issues. The only thing on the RCD that is external is an outside socket under a carport. This was inspected and tested, bone dry and testing fine.

In short, clean bill of health.

electrichunter

did he do insulation resistance , i had job lately rcd tripping,. the continunity tester showed up nothing and i was using a low ohm on multifuntion . so done insulation and short showed between live and earth ,not enough to take out mcb only rcd. a link between last 2 sks why is it always the last ones if i started that end ha it would be at the first in circuit!!!!