Neighbour's power tools tripping my RCD?

[ceecjc1]

The electrician came this morning and it was indeed a different guy. He spent a couple of hours here testing everything and was very much more thorough than the last.

The 30mA RCDs are not bridged. Both function perfectly and he did a lot of tests from both the CU and various sockets to check. The 100mA RCD refused to trip no matter what he did, which is the opposite to what I expected and hoped to happen (because it would prove a fault if it tripped at a low current, for example).

He replaced the 100mA RCD anyway and could get the new one to trip, so perhaps the old one was somehow faulty.

The only other suspicious behaviour was the N-E resistance was high on every circuit apart from on the kitchen circuit which was 1.3MOhm - low but not low enough to be a problem. It sounds high to me but apparently it's only a problem if it's below 1. These tests were performed with everything unplugged apart from the fridge freezer, which is too heavy to move.

 

[JohnW2]

The electrician came this morning and it was indeed a different guy. He spent a couple of hours here testing everything and was very much more thorough than the last. The 30mA RCDs are not bridged. Both function perfectly and he did a lot of tests from both the CU and various sockets to check. The 100mA RCD refused to trip no matter what he did, which is the opposite to what I expected and hoped to happen (because it would prove a fault if it tripped at a low current, for example). He replaced the 100mA RCD anyway and could get the new one to trip, so perhaps the old one was somehow faulty.

Thanks for the update That's all very interesting. At least it sounds as if you probably had a competent electrician this time!

The only other suspicious behaviour was the N-E resistance was high on every circuit apart from on the kitchen circuit which was 1.3MOhm - low but not low enough to be a problem. It sounds high to me but apparently it's only a problem if it's below 1. These tests were performed with everything unplugged apart from the fridge freezer, which is too heavy to move.

Well, 1.3MΩ is pretty high in many senses, but low in terms of the 'hundreds of MΩ' one expects of intact wiring. However, if the FF was connected when he undertook that test, it might well explain the reading. Can you really not unplug the FF without moving it?

I guess you now have to sit back and wait, and/or encourage your neighbour to use some power tools!

Kind Regards, John

 

[ceecjc1]

Well, 1.3MΩ is pretty high in many senses, but low in terms of the 'hundreds of MΩ' one expects of intact wiring. However, if the FF was connected when he undertook that test, it might well explain the reading. Can you really not unplug the FF without moving it?

Yeah, he said it should be >200MΩ so 1.3MΩ is low but not low enough to need to fix.

The FF is a huge double door thing and the socket is right in the middle behind it.

He also reiterated, same as you guys, that the chances of the neighbour's drill affecting our RCD were vanishingly small.

 

[JohnW2]

The FF is a huge double door thing and the socket is right in the middle behind it.

Fair enough - although that would obviously not be too clever if 'anything' nasty every happened to it!

He also reiterated, same as you guys, that the chances of the neighbour's drill affecting our RCD were vanishingly small.

It terms of true 'fault paths', that's certainly true - some of the ideas which have been thrown about (admittedly 'in desperation') were pretty esoteric. However, particularly if the RCD concerned were 'faulty', it might have in some way been susceptible to 'spikes' in the supply. As ericmark suggested, and as the electrician has done, the sensible course was probably always going to be to replace the 100mA RCD, more-or-less regardless of what the testing revealed.

Kind Regards, John

 

[stillp]

- months ago, when I plugged my jigsaw into a certain socket, it would trip the RCD every time. After moving to a different socket the RCD stops tripping.

Has this stopped happening?

 

[ceecjc1]

- months ago, when I plugged my jigsaw into a certain socket, it would trip the RCD every time. After moving to a different socket the RCD stops tripping.

Has this stopped happening?

I haven't used my jigsaw in that socket since it kept tripping the RCD but the electrician suggested we test it just to see what would happen....and it didn't trip.

It's possible the jigsaw had a transient problem, loose connection or whatever, which resolved itself coincidentally when I moved it to a different socket. It was £9.99 from B&Q so it's possible the jigsaw was the problem. I've used it successfully many times since then though.