RCD tripping on mains outage.

Yeah, I had thought of wiring a separate circuit for the freezer, as it happens there's an easy route from the fuse board. In previous times I'd have run this myself, but now I'd get a RECI. If all else fails that's what I'll do, as we're regularly away, from spring onwards.

However, I'd still lose remote access to cameras, lights and heating and the heating itself, so not ideal.

I'd really like to get to the bottom of this but I no longer have access to test equipment - hence my post here. I suspect there may be power surges from heavy duty farming equipment, but I've no way of checking.

The RCD was not tested AFAIK - I wasn't standing over his shoulder. The electrician told me he did an insulation test on the wiring and verified the earthing was ok.

The RCD resets under load, I've checked this many times. I've also used a clamp meter to check for leakage, which is negligible. The issue appears to be directly related to the quality of the mains - I've been in the house when the mains was briefly interrupted and the RCD tripped, likewise for mains outages.

Anyway,, I'll get the RCD replaced, as suggested; and the freezer on a dedicated circuit.

Thanks guys, that's exactly the type of response I was hoping for. I don't believe for a second that the existing RCD is faulty but the scenario you outline above sounds very plausible. I can't think of any other one. Before going away I unplugged everything but the fridge and freezer, both of which are new. The immersion and cookers/hob were isolated at their switches as were the showers. It still tripped, on a power outage. at other times it has worked for a number of months, without issue.

I don't see any real advantage in replacing the current unit with a random unit that the electrician has handy. How common are circuit-based RCD's and how can they be identified? I'm prepared to source one myself, if necessary. If this works I'll also add one to the circuit for the freezer.

I too had wondered whether surge protection would be of any benefit. I'm not too worried about lightening, as the final feed to the house is underground. However I suppose it could provide some protection against power surges. It's a road I'd rather avoid, if possible. For maximum effectiveness the earthing requirements are pretty onerous, and not so easy to implement.

I'm not sure what your point is, electrocution in any domestic setting in Ireland is extremely rare. However, even one death is too much, if it is easily preventable.

In my previous house I installed separate RCDs for the shower, fridge/freezer, lights and external socket in the boiler house. With a young family, I erred on the side of caution. Might seem excessive but my sister in law's husband was electrocuted, when I was a teenager. It was not his fault, there were multiple installation failures by professionals; at a house where he was working. He left behind a widow and a young family.

I measured for phase neutral imbalance at each individual circuit, under load, with all loads on other circuits removed. I also checked for earth leakage on each individual circuit and at bonding to exposed metalwork. Maybe my methodology was flawed and I'm open to suggestions - I'm retired, so plenty time on my hands. :)

The RCD only trips when there is a mains outage, even if this is momentarily. Even then it doesn't always trip. I would love to move to multiple RCBO's, as you suggest. However, getting an electrician to do this, at reasonable cost, is unlikely in the current climate.