TRIPPING RCD diyer!!

Simo4567 · Aug 23, 2021

Hi all, I have a very random problem and wondering if anyone maybe able to shed some light on this issue.
When my next door neighbour uses his leaf blower it trips my main RCD! He uses it plugged into his garage and has a surge protection plug that it's plugged into. When he starts up the blower it immediately trips ours, but not his? Doesnt happen with the mower or pressure washer. And it doesn't happen every time, but more often than not. I had an electrician test our board and check everything was safe and working correctly and he confirmed it was, he was baffled and had no clue what could be wrong.

So what on earth could be happening here? I have no real knowledge of electrics so any technical terms will be lost on me!!
I guess I should change the main RCD? But if this was faulty I suppose it would trip more often?

Any ideas would be great. Thanks

James · Aug 23, 2021

Simo4567 said:
Hi all, I have a very random problem and wondering if anyone maybe able to shed some light on this issue.
When my next door neighbour uses his leaf blower it trips my main RCD! He uses it plugged into his garage and has a surge protection plug that it's plugged into. When he starts up the blower it immediately trips ours, but not his? Doesnt happen with the mower or pressure washer. And it doesn't happen every time, but more often than not. I had an electrician test our board and check everything was safe and working correctly and he confirmed it was, he was baffled and had no clue what could be wrong.

So what on earth could be happening here? I have no real knowledge of electrics so any technical terms will be lost on me!!
I guess I should change the main RCD? But if this was faulty I suppose it would trip more often?

Any ideas would be great. Thanks

This is an interesting problem,
a house i was renting some years ago had a similar issue.
next door would start there lawn mower and the house 2 doors away would have an rcd trip.

both property's were TT and as far as I could tell there were no interconnecting cables.

I never got to the bottom of it and it has been one of those strange occurrences that i have pondered on for some time.

I know a little bit about how Electricity and RCD's work but could not fathom where the fault was on that one and unfortunately, in my humble opinion, this problem of yours is going to take quite some time to figure out.

Dartlec · Aug 23, 2021

Is this one main RCD covering the whole house? Is it a 30mA?

Assuming your RCD is not faulty, then clearly it is detecting an imbalance of flow at the time next door's lead blower starts up.

Assuming that there isn't any interconnection between your actual cables, then it's likely to be some sort of issue with induced current or harmonics, which is well above my experience and knowledge.

Fortunately, there are some on here who likely will understand and hopefully give some clues...

If it is a whole house RCD, then it may well be that with all the circuits in your own house on, it might be quite close to its tripping current already - such that whatever is happening from next door is enough to put it 'over the top'.

You could try an experiment - turning off all the circuits on that RCD at the MCBS(Fuses) but leaving the RCD on, and then see if next door trips it.

If it does, then the solution is likely to put fewer circuits on that RCD by adding another one, or even better putting RCBOs on each circuit to minimise the amount of leakage on any one RCD/RCBO.

pc1966 · Aug 23, 2021

My first suspicion is a N-E fault in your property. That should be easy to check for by anyone with an IR tester (and knowledge of how to use it).

Other possibility is it is higher frequency noise, perhaps harmonics, perhaps commutator arcing, that is causing enough AC leakage to trip you RCD. I can't see that being down only to the leaf blower, but it might be that your house has enough cumulative leakage to be close to the RCD's trip point.

Again, someone with a MFT (to ramp-test the RCD) and a suitable clamp ammeter to measure your base-line leakage current out to be able to check that possible reason out.

Lucien Nunes · Aug 23, 2021

I agree that a neutral-earth fault in your wiring is a likely cause. If the electrician did a comprehensive test of your installation, it should have shown up, however you mention 'tested the board' so I am not sure what he tested.

This type of fault makes your RCD react to voltage between neutral and earth because any difference in potential drives current through the fault which the RCD (correctly) detects as an imbalance. Although the fault would be on a circuit protected by the RCD that trips, the cause of the voltage difference - typically a heavy load or one with a high startup current such as the blower - can be anywhere. If the supply to both properties is TN-S, i.e. the neutral and earth are separate conductors from the supply and not linked within the service head, then the load that drives the current through your neutral-earth fault could be next door.

There would be no reason to expect his RCD to trip if the fault is in your wiring. It is however suprising that other heavy loads like cookers and showers in your property, and the pressure washer next door, are not having a similar effect. But depending on where the fault is, these things can be very pattern-sensitive. You might find that if you switch on everything you have, it does trip. But the fact that the blower trips it specifically at startup, and because you say it does not always trip I infer that once the blower is running it can continue to run without tripping, that is a strong clue that it is high current load that is the trigger factor which is what you expect of an N-E fault.

I would definitely do an insulation resistance test on your wiring first, if only to rule this out.

OnlQQker · Aug 24, 2021

Does it still trip if he uses another leaf blower?

Kind of odd it only does it when he uses his leaf blower...

pc1966 · Aug 24, 2021

Lucien Nunes said:
I agree that a neutral-earth fault in your wiring is a likely cause. If the electrician did a comprehensive test of your installation, it should have shown up, however you mention 'tested the board' so I am not sure what he tested.

It is also possible they tested the fixed wiring with all stuff off / unplugged, but actually a N-E fault is present in some appliance and not the house wiring.

Simo4567 · Aug 24, 2021

OnlQQker said:
Does it still trip if he uses another leaf blower?

Kind of odd it only does it when he uses his leaf blower...

I have yet to try this. I did think about getting him one for Christmas! It's lucky we get on well and they have a key so if we are away and he uses it, he'll pop round and reset it.

Simo4567 · Aug 24, 2021

Dartlec said:
Is this one main RCD covering the whole house? Is it a 30mA?

Assuming your RCD is not faulty, then clearly it is detecting an imbalance of flow at the time next door's lead blower starts up.

Assuming that there isn't any interconnection between your actual cables, then it's likely to be some sort of issue with induced current or harmonics, which is well above my experience and knowledge.

Fortunately, there are some on here who likely will understand and hopefully give some clues...

If it is a whole house RCD, then it may well be that with all the circuits in your own house on, it might be quite close to its tripping current already - such that whatever is happening from next door is enough to put it 'over the top'.

You could try an experiment - turning off all the circuits on that RCD at the MCBS(Fuses) but leaving the RCD on, and then see if next door trips it.

If it does, then the solution is likely to put fewer circuits on that RCD by adding another one, or even better putting RCBOs on each circuit to minimise the amount of leakage on any one RCD/RCBO.

Thank you I will look into this with this advice. Here is the main rcd.

Simo4567 · Aug 24, 2021

Lucien Nunes said:
I agree that a neutral-earth fault in your wiring is a likely cause. If the electrician did a comprehensive test of your installation, it should have shown up, however you mention 'tested the board' so I am not sure what he tested.

This type of fault makes your RCD react to voltage between neutral and earth because any difference in potential drives current through the fault which the RCD (correctly) detects as an imbalance. Although the fault would be on a circuit protected by the RCD that trips, the cause of the voltage difference - typically a heavy load or one with a high startup current such as the blower - can be anywhere. If the supply to both properties is TN-S, i.e. the neutral and earth are separate conductors from the supply and not linked within the service head, then the load that drives the current through your neutral-earth fault could be next door.

There would be no reason to expect his RCD to trip if the fault is in your wiring. It is however suprising that other heavy loads like cookers and showers in your property, and the pressure washer next door, are not having a similar effect. But depending on where the fault is, these things can be very pattern-sensitive. You might find that if you switch on everything you have, it does trip. But the fact that the blower trips it specifically at startup, and because you say it does not always trip I infer that once the blower is running it can continue to run without tripping, that is a strong clue that it is high current load that is the trigger factor which is what you expect of an N-E fault.

I would definitely do an insulation resistance test on your wiring first, if only to rule this out.

Thank you. This will definitely be helpful.

Mikegh · Aug 24, 2021

Dartlec said:
Is this one main RCD covering the whole house? Is it a 30mA?

Assuming your RCD is not faulty, then clearly it is detecting an imbalance of flow at the time next door's lead blower starts up.

Assuming that there isn't any interconnection between your actual cables, then it's likely to be some sort of issue with induced current or harmonics, which is well above my experience and knowledge.

Fortunately, there are some on here who likely will understand and hopefully give some clues...

If it is a whole house RCD, then it may well be that with all the circuits in your own house on, it might be quite close to its tripping current already - such that whatever is happening from next door is enough to put it 'over the top'.

You could try an experiment - turning off all the circuits on that RCD at the MCBS(Fuses) but leaving the RCD on, and then see if next door trips it.

If it does, then the solution is likely to put fewer circuits on that RCD by adding another one, or even better putting RCBOs on each circuit to minimise the amount of leakage on any one RCD/RCBO.

I saw something related before where a luminaire on a non RCD protected way was tripping the RCD when you switched it off if I recall correctly

Anyway I couldn't make sense of it ,but my inspector said it was harmonics I think(above my pay grade these days)

Anyway he said try it without the capacitor and it stopped the nuisance

Dartlec · Aug 24, 2021

Simo4567 said:
Thank you I will look into this with this advice. Here is the main rcd.

This may or may not be related to the issue, but that's a cheap and not particularly nice brand of RCD and it may also have been overloaded at periods which could affect it's reliability.

It's rated to 63A but looking at the circuits you may well have more than that, although in practise you probably won't be using more than 63A for any length of time.

I assume when things were tested, that the RCD was checked to ensure it tripped within suitable times? And that it trips if you press the test button?

It does appear that you have everything on that one RCD, so with a few 'leaky' devices you may well be quite close to the tripping point most of the time, especially if that RCD is particularly sensitive.

That still shouldn't mean that next door should trip it, so worth checking for the Neutral to Earth fault as mentioned by others, but it may not be helping.