EFLI, you have become rather quiet since I replied to your question - what do you feel about my response?
Kind Regards, John
Neighbour's power tools tripping my RCD?
- Thread starter ceecjc1
- Start date
Kind Regards, John
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I'm still a bit confused, to be honest.
I may have missed something fundamental in the possible scenario where current on the neutral from outside could cause the 100mA RCD to trip (assuming the 30A is faulty) with a 500Ω leak.
Surely a fault between neutral and earth of 500Ω would cause it to trip during normal usage. 230V/500Ω = 460mA.
Is this not comparable with a person with 1,000Ω body resistance touching the neutral?
Would not the RCD trip?
I may have missed something fundamental in the possible scenario where current on the neutral from outside could cause the 100mA RCD to trip (assuming the 30A is faulty) with a 500Ω leak.
Surely a fault between neutral and earth of 500Ω would cause it to trip during normal usage. 230V/500Ω = 460mA.
Is this not comparable with a person with 1,000Ω body resistance touching the neutral?
Would not the RCD trip?
Forget about that for a moment. Although it's the underlying issue, the question you asked is more basic, and rather different (i.e. nothing to do with any 'current from outside' {of the installation} ).
Mr Ohm would be proud of you - but only if the potential difference between your neutral and earth were 230V - which I don't imagine is what you expect to see, is it?
I don't know about yours, but even with quite high loads operating, my neutral is rarely more than a volt or two above my installation's 'earth' potential (at origin of installation) - let's say 5V to be generous (indeed, if you have TN-C-S it's hopefully zero at the origin!). Per Mr Ohm again, a 500Ω N-E fault would therefore then result in a current of 10mA following through that fault, hence only a 10 mA imbalance in the RCD - not enough to trip it.
Even if you moved a long way from the origin, to the end of a final circuit loaded so as to produce the maximum permissible VD (5.75V in neutral), you still should only have that 5.75V N-E pd with TN-C-S, potentially a bit more with other earthing systems.
Just touching the neutral (and earth)? Definitely not, unless there was something very wrong with your installation. Per above, if one assumes a 5V N-E pd, only 5mA would pass through you to earth, far too little to trip a 30mA RCD. To get 30mA through you would obviously require an N-E pd of 30V - which is most unlikely to exist under normal circumstances.
... does the above make sense?
Kind Regards, John
I am either having a blonde moment (day) or ...
My point is that if the above fault situation causes the RCD to trip because of outside influences then it will cause the RCD to trip when the installation is being used normally.
(As you know) the RCD monitors residual current; it is not dependent on a potential between neutral and earth or CPC.
Any fault between neutral and earth less than 2,300Ω for a 100mA RCD or 7,666Ω for 30mA will/should cause it to trip.
Is that not correct?
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If there is no potential difference between neutral and earth then there can be be no fault current flowing from neutral to earth.
There will only be a fault current at those levels if the neutral potential is 230 volts above earth potential.EFLImpudence said:
Unless it's me who is, I think you probably are
No. If you introduce a fault (resistance) between N and E, per Mr Ohm's well-know law, what current flows through that fault/resistance will depend upon the voltage across it (i.e. the N-E voltage). As I said, under normal load conditions, you're unlikely to get more than a volt or two between N-E, hence very low current through that 500Ω resistance, not enough to trip the RCD. Bernard was postulating a 150A+ inrush current (far more than the 'normal load') into the neighbour's motor, increasing the N-E voltage (to both properties) enough for the current through fault to be large enough to create a sufficient imbalance for the RCD to trip.
Yes, but if you're talking about an N-E fault, then (per Mr Ohm) the current through that fault, hence the L-N current imbalance in the RCD will be dependent upon (directly proportional to) the magnitude of the N-E potential difference.
No - this seems to be the same 'blonde moment' you were having this afternoon. Your sums are assuming that there is 230V between N and E to drive those currents (100mA or 30mA) through the fault resistances you mention. As I've said, in practice, that will usually only be a volt or two - never anything like 230V. You appear to be thinking of L-E faults, not N-E ones - when, of course, there will be a full 230V to drive current through the fault resistance (and your sums would be correct).
Kind Regards, John
Hi guys,
Just following your very interesting discussion and thought I would update from my end. The electrician came round to visit but identified no problem and said that it was very unlikely the RCD tripping could be related to the neighbour's house in any way.
He also said that the 100mA RCD was "more sensitive than the 30mA ones" which is why they didn't trip. This didn't make sense to me but he's the expert, not me. He also suggested that the vibrations from the power tools could be affecting a faulty power connection outside his house, leading to our house, to cause an RCD trip.
The neighbour only bought the property at the start of October and that's around about when we started having RCD trips. Most interestingly, he started up a power drill this morning (not the floor sander as was the problem, last time) and our RCD tripped almost immediately. His drill kept going but he didn't drill for long and once reset the RCD hasn't gone off again. Our suspect dishwashwer was not on at the time, but the washing machine was.
Just to recap:
- the RCD trips frequently while the neighbour is using power tools. It can now be said that our washing machine has always been on when this happens, but I don't know if that is related.
- 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.
- the RCD hasn't otherwise tripped in over a week, with both washing machine and dishwasher on
- it is always the 100mA RCD which trips, never the 30mA.
The overhead power seems to go to my neighbour's house and then into mine, though he has a single cable and we have two (L/N). The earth is buried in the ground by the front door.
I'd go round to talk to the neighbour but I have no idea what to say to him, let alone what I expect him to do.
Thanks,
Chris
Just following your very interesting discussion and thought I would update from my end. The electrician came round to visit but identified no problem and said that it was very unlikely the RCD tripping could be related to the neighbour's house in any way.
He also said that the 100mA RCD was "more sensitive than the 30mA ones" which is why they didn't trip. This didn't make sense to me but he's the expert, not me. He also suggested that the vibrations from the power tools could be affecting a faulty power connection outside his house, leading to our house, to cause an RCD trip.
The neighbour only bought the property at the start of October and that's around about when we started having RCD trips. Most interestingly, he started up a power drill this morning (not the floor sander as was the problem, last time) and our RCD tripped almost immediately. His drill kept going but he didn't drill for long and once reset the RCD hasn't gone off again. Our suspect dishwashwer was not on at the time, but the washing machine was.
Just to recap:
- the RCD trips frequently while the neighbour is using power tools. It can now be said that our washing machine has always been on when this happens, but I don't know if that is related.
- 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.
- the RCD hasn't otherwise tripped in over a week, with both washing machine and dishwasher on
- it is always the 100mA RCD which trips, never the 30mA.
The overhead power seems to go to my neighbour's house and then into mine, though he has a single cable and we have two (L/N). The earth is buried in the ground by the front door.
I'd go round to talk to the neighbour but I have no idea what to say to him, let alone what I expect him to do.
Thanks,
Chris
Chris,
You could start by asking the neighbour if he is getting any bizarre RCD tripping.
Other than that, you need a better electrician (i.e. one wo is better at fault finding, and who knows that 100>30!), and you need him to find the reason why your jigsaw tripped the RCD when in some sockets but not in others.
You could start by asking the neighbour if he is getting any bizarre RCD tripping.
Other than that, you need a better electrician (i.e. one wo is better at fault finding, and who knows that 100>30!), and you need him to find the reason why your jigsaw tripped the RCD when in some sockets but not in others.
Do I take it that his investigations included testing both your RCDs? As discussed before, one of the more likely (and worrying) explanations for the 100mA one tripping when the 30mA didn't would be that the latter was faulty.
Other than being one way of stating the obvious (given that the 100mA trips when the 30mA one doesn't), it doesn't make any sense to me, either.
That does not make a lot of sense, either. Even if (seemingly pretty unlikely) you neighbour's power tools were vibrating faulty joints, that in itself should not cause your RCD to trip.
That's perhaps the most odd bit. If the primary fault causing the trip is within your installation (even if augmented/'aided and abetted' by happenings next door), then one would expect the 30mA, not 100mA to trip - partially because 100mA>30mA (but that's not foolproof) but primarily because your 100mA is deliberately 'time-delayed' to allow the 30mA one to trip without the 100mA one tripping. That's why I asked above if you are certain that he tested the 30mA one and found it to be working OK.
Whatever, it is clear that something is 'not right', so maybe you need an electrician who is 'more expert' than the one you've had?!
Kind Regards, John
He tested all the RCDs by pushing the test button a few times and making sure they tripped. Does this count? He also pulled out some wires from the consumer unit and tested, I think, the N-E connections for leakage.
The problem is this is a rented property and the landlord / managing agent supply the electrician so to get a different one I need to somehow argue that this guy wasn't "expert enough". Their current advice is to call the power supply company and get them to check the loose connection. This seems like a waste of time to me, but since I'm not the expert here it's hard for me to tell them to send a different guy back.
Cheers,
Chris
No - he should have tested them properly, with test equipment.
That sounds appropriate - although it obviously would not necessarily detect a N-E fault which was 'intermittent'.
That's a bit of a problem - although I suppose that the fact taht he has failed to diagnose the problem could be taken to indicate that he is not 'expert enough'! You could also cite (if you're sure) the fact that he didn't even test the RCDs properly - which seems like a pretty good indication of incompetence, given that the problem is all about RCDs tripping (or, in the case of the 30mA one, not tripping)!
Sounds like a waste of time to me, too - but if it serves to humour them, then maybe the thing is to go along with that, which will probably bring you back to square one - with it then being more difficult for them to argue that you don't need a 'better electrician'!
Kind Regards, John
I tried to get another visit from another electrician but no chance. The electrician says "it's definitely a loose connection" so I'll have to get Scottish&Southern on the case before I go back to the agents. Pity that will take 4-8 weeks according to their website!
That's a pity. It looks like you'll have to wait whilst you 'go through those motions', but next time you really need an electrician who doesn't think it likely, let alone 'definite', that a loose connection somewhere can cause an RCD to trip in someone else's house!
Kind Regards, John
Have followed with interest the RCD (etc) discussions and have no comments there due to my limited knowledge.
Assuming a
The OP's description of neighbour needs a bit more clarification. Is this a semi or terrace house? If so, is it possible that there has been a connection made between the two via, say, a loft light, aerial, outside light, cellar or through the dividing wall? There would still need to be a fault of course, but it could be simple to find (?)
When the electrician called did he look just at the OP's house or call at the neighbours?
Assuming a
The OP's description of neighbour needs a bit more clarification. Is this a semi or terrace house? If so, is it possible that there has been a connection made between the two via, say, a loft light, aerial, outside light, cellar or through the dividing wall? There would still need to be a fault of course, but it could be simple to find (?)
When the electrician called did he look just at the OP's house or call at the neighbours?
Have followed with interest the RCD (etc) discussions and have no comments there due to my limited knowledge.
Assuming a RCD problem can be sorted as being a faulty unit, then perhaps there is another way of looking at the original problem?
The OP's description of neighbour needs a bit more clarification. Is this a semi or terrace house? If so, is it possible that there has been a connection made between the two via, say, a loft light, aerial, outside light, cellar or through the dividing wall? There would still need to be a fault of course, but it could be simple to find (?)
When the electrician called did he look just at the OP's house or call at the neighbours?
Assuming a RCD problem can be sorted as being a faulty unit, then perhaps there is another way of looking at the original problem?
The OP's description of neighbour needs a bit more clarification. Is this a semi or terrace house? If so, is it possible that there has been a connection made between the two via, say, a loft light, aerial, outside light, cellar or through the dividing wall? There would still need to be a fault of course, but it could be simple to find (?)
When the electrician called did he look just at the OP's house or call at the neighbours?
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