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Spurious RCD trips

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I'm having a problem with my RCD 'Safe-T-Cut' spuriously tripping. This happens at random times, seemingly uncorrelated with any activity - morning, afternoon, evening, night, completely unpredictable. This happens every few days - the RCD trips and can be immediately reset. OK for several days before tripping again. The fault - if indeed there is a fault - is obviously transient in nature.

The usual advice is to isolate various circuits and turn off appliances to try to isolate the cause but this is obviously impractical when the trip only happens infrequently. I can hardly just disconnect the fridge/freezer for a week to see what happens - and this would not prove anything anyway!

i am wondering if the RCD unit itself is developing a fault or is just oversensitive to mains spikes or general voltage instability? It's only a minor inconvenience - unless in the middle of the night - but I would like to get it sorted out.

Anyone out there experienced any similar behaviour? Any suggestions?

The house has no ground circuit, if this is relevant.

You should probably sort out a ground for your Class-1 appliances, but that's unlikely to be your issue.

Is the Safe-T-Cut one of the adjustable ones? What is it set to?

Do you have any test gear, a multimeter, neon driver etc?

Start by popping off your outlets and switches and check for wildlife and/or dampness inside.

"I don't want to know why you can't. I want to know how you can!"

  • Author
14 minutes ago, Crossy said:

You should probably sort out a ground for your Class-1 appliances, but that's unlikely to be your issue.

Is the Safe-T-Cut one of the adjustable ones? What is it set to?

Do you have any test gear, a multimeter, neon driver etc?

Start by popping off your outlets and switches and check for wildlife and/or dampness inside.

Set to 30mA

I have a clamp meter and have tested everything that I have access to for leakage currents. Nothing untoward shows up.

No wildlife - ants or whatever - found in switches or sockets.

The real mystery is why this happens only infrequently.

I'll bet you have a Neutral - Earth (the actual earth since you're not wired for grounds) fault somewhere, they can be an absolute dog to locate even with the correct test gear, you stand no chance with a regular multimeter.

One thing, have you verified the polarity of your incoming supply (live really is live)? It wouldn't be the first time that odd problems have been traced to swapped incoming supply.

"I don't want to know why you can't. I want to know how you can!"

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