GFCI tripping every 2-3 hours

[myprivate]

Only the main incoming GFCI is tripping, the other CB are not. Tried isolating individual CB's and the problem does not seem to be linked to any particular circuit. I suspect the GFCI is faulty because I had one fail about 7 years ago. So here's the question, I switched the GFCI over to 'DIRECT' setting but it still tripped after about 2 hours, so does this indicate that it is the probably the GFCI that is faulty?

[Crossy]

If it's still tripping on "Direct" (which bypasses the RCD section) then yes, there's a good chance that it's failed

What is the current rating (Amps) of the unit and of your main breaker? What meter do you have? Is it going round like the clappers? (just to verify the RCBO isn't opening on over-current).

[myprivate]

GFCI and Main Breaker are both 50A. It trips normally I'd say, not unusually loud.

[myprivate]

Meter doesn't seem to be moving much

[myprivate]

After the Main Breaker there are 11 sub breakers ranging from 10 to 32 Amps. If there is over current wouldn't one of those trip first especially when the Market n GFCI is in direct mode.

[myprivate]

Some more potential clues....switched the GFCI to lowest setting (5mA) with all the sub breakers switched off. Slowly turn on the breakers one by one and the GFCI immediately trips after about 6 are on (don't have to wait 2-3 hours this method). Tried different combinations and sequences and it doesn't seem to be linked to any particular sub breaker.

[bankruatsteve]

Just for the hell of it... try turning off your RCD breaker then turn on/off the Square-D main breaker about 10 times.

Does the RCD trip when set to 30mA?

[myprivate]

Just for the hell of it... try turning off your RCD breaker then turn on/off the Square-D main breaker about 10 times.

Does the RCD trip when set to 30mA?

No, the RCD didn't trip.

I also tried it the other way around - with RCD on and all sub breakers on I flipped the Square D on/off about 10 times, the RCD didn't trip. So it doesn't seem to be an in-rush issue.

[bankruatsteve]

So, does it still trip if you repeat what you did before? I wasn't thinking over-current but perhaps something dodgy in the Square-D main breaker. Another just for the hell of it... remove the cover of the Square-D, power off, and give it a good vacuum.

The fact that your RCD tripped even when on direct (is that right?) is a bit mysterious though.

Edited June 19, 2016 by bankruatsteve

[myprivate]

Yep still trips fast at 5mA with about 6 of the 11 breakers on, now it is set at 25mA and back on the 2-3 hour trip cycles. I've tried turning off intermittent things like the water pump to try to isolate the problem but it makes no difference. The RCD trips on direct mode every 2-3 hours (in other words it makes no difference if set to 25mA or Direct), but none of the sub breakers tripped, this is what makes me think the RCD is faulty.

[bankruatsteve]

It sure seems that's the problem. That's where I take a hammer and bang on it. That actually works some times.

[Crossy]

Ah, the "engineer's thump" Steve, most effective, used it many times myself.

Unfortunately it's very difficult to test these things without specialist equipment (and even then it's not always conclusive).

Random tripping is usually diagnosed by substitution.

[myprivate]

Just for the hell of it... try turning off your RCD breaker then turn on/off the Square-D main breaker about 10 times.

Does the RCD trip when set to 30mA?

No, the RCD didn't trip.

I also tried it the other way around - with RCD on and all sub breakers on I flipped the Square D on/off about 10 times, the RCD didn't trip. So it doesn't seem to be an in-rush issue.

It has not tripped since I did this. Fingers crossed for an air conditioned night.

[bankruatsteve]

Just for the hell of it... try turning off your RCD breaker then turn on/off the Square-D main breaker about 10 times.

Does the RCD trip when set to 30mA?

No, the RCD didn't trip.

I also tried it the other way around - with RCD on and all sub breakers on I flipped the Square D on/off about 10 times, the RCD didn't trip. So it doesn't seem to be an in-rush issue.

It has not tripped since I did this. Fingers crossed for an air conditioned night.

So, you didn't have to use the hammer? In any case, the "fix" may have been simply dislodging <something> (ants, dust, gecko stuff) that provided a nebulous path for current to go where it should not. If you didn't give your boxes a vac, you still might consider doing that.

[myprivate]

No hammer, and no problems overnight. Hopefully whatever was causing the leakage has been dislodged. Thanks for that.