Neighbour's power tools tripping my RCD?

[ceecjc1]

Hi folks,

I've had a read through the forum and the answer to my question seems to be "yes", but I thought I'd ask to be sure.

The RCD in my house tripped repeatedly today (4-5 times per session) when the neighbour was sanding his floors using some kind of power tool. Is it possible that his power tools are causing my RCD to trip? I know his RCD isn't tripping because his sanding continues uninterrupted. I have a jigsaw myself which has tripped my RCD in the past but only when connected to a certain socket.

The RCD had been tripping occasionally (once or twice a week) over the last few weeks while the dishwasher was on and I was beginning to suspect a dodgy looking dishwasher element but due to the frequency of the trips today I'm now suspecting my neighbour.

My house was rewired a few years ago (not sure how recently exactly, it was done before I moved here). The house has overhead power and TT earth (which is buried into the ground next to the front door).

I've attached a picture of the consumer unit showing the 30mA RCDs for each of circuit A and B, as well as the 100mA RCD for the full house. Note that the 30mA RCDs do not trip and it's the 100mA one which always needs reset.

So, my question to all of you experts is: could the neighbour be tripping my RCD and does this mean I have a dodgy RCD? Is it odd that the 100mA trips but the 30mA doesn't?

Thanks,
Chris

Untitled

• ceecjc1
• 20 Oct 2013
• 1

 

[JohnW2]

So, my question to all of you experts is: could the neighbour be tripping my RCD and does this mean I have a dodgy RCD? Is it odd that the 100mA trips but the 30mA doesn't?

Whether your neighbour's power tools have got anything to do with it or not, it certainly sounds as if your 100mA RCD has become 'trigger happy' (i.e. 'dodgy'). If anything within your house's electrical installation was resulting in a leakage which could cause an RCD to trip, one of the 30mA ones really ought to go first (I presume that the 100mA one is 'time delayed').

Kind Regards, John

 

[PrenticeBoyofDerry]

it certainly sounds as if your 100mA RCD has become 'trigger happy' (i.e. 'dodgy'). If anything within your house's electrical installation was resulting in a leakage which could cause an RCD to trip, one of the 30mA ones really ought to go first

Unless the 30mA RCCB is faulty, therefore you could expect the 100mA to trip on excessive earth leakage.

(I presume that the 100mA one is 'time delayed').

It is
I would be looking at sorting out faulty socket outlet and repairing any fault that the dishwasher may have.

 

[WellKnownSid]

There are usually one or two components inside an RCD which help prevent nuisance tripping - these can sometimes fail (or they forget to fit them on the production line ) which results in the fault you describe...

However... RCD tolerances are quite wide - it's theoretically possible that you have leakages across the two 30mA protected circuits high enough to trip the 100mA device but not the others. RCDs also respond to upstream effects as well as downstream ones, which could be causing the 100mA device to respond in preference.

Any safety device which is suddenly tripping warrants further investigation regardless as to whether it's the device at fault or not, an electrician will be able to figure out what's going on...

 

[RF Lighting]

Yes it's a type S (time delayed) RCD, but there's no need for it to be there at all.

I'd get an electrician to give your installation a quick going over and make sure everything looks ok, ensure the 30mA devices are working correctly, and remove the 100mA RCD.

It's vanishingly improbably that your neighbours sander is causing your problem, especially as you say it's tripped when he hasn't been sanding!

 

[RF Lighting]

There are usually one or two components inside an RCD which help prevent nuisance tripping - these can sometimes fail (or they forget to fit them on the production line ) which results in the fault you describe...

Are there? What are they then?

 

[JohnW2]

it certainly sounds as if your 100mA RCD has become 'trigger happy' (i.e. 'dodgy'). If anything within your house's electrical installation was resulting in a leakage which could cause an RCD to trip, one of the 30mA ones really ought to go first

Unless the 30mA RCCB is faulty, therefore you could expect the 100mA to trip on excessive earth leakage.

True - but, as you say, it would probably have to be quite a substantial (i.e. probably 'real', rather then 'nuisance' trip) for a 100mA one to trip.

(I presume that the 100mA one is 'time delayed').

It is

Indeed it is

I would be looking at sorting out faulty socket outlet and repairing any fault that the dishwasher may have.

TBH, I'd probably test the RCDs first - but, after that, as you say.

Kind Regards, John

 

[JohnW2]

There are usually one or two components inside an RCD which help prevent nuisance tripping - these can sometimes fail (or they forget to fit them on the production line ) which results in the fault you describe...

Are there? What are they then?

Filtering capacitors, for a start - assuming that it's an electrically-triggered RCD.

Kind Regards, John

 

[PrenticeBoyofDerry]

TBH, I'd probably test the RCDs first - but, after that, as you say.

Yes priority would be to diagnose any fault to RCD.
As RFL has already mentioned there is no real need for the 100mA unit, but maybe on this occasion, if one or both 30mA units are faulty, it would have offered some form of secondary protection.

 

[JohnW2]

Yes it's a type S (time delayed) RCD, but there's no need for it to be there at all. I'd get an electrician to give your installation a quick going over and make sure everything looks ok, ensure the 30mA devices are working correctly, and remove the 100mA RCD.

As you say, the 100mA RCD is theoretically 'unnecessary'. However, if PBoD's theory is correct, and a genuine intermittent fault resulting in >100mA earth leakage is failing to cause a (faulty) 30mA RCD to operate, this surely is an example of the 'value' of having 'belt and braces' RCDs, isn't it?

So long as both the 30mA RCDs are functioning correctly, the Type S will (theoretically!!) never operate, so it's presence really has no true downsides. Hence, if it were me, and the 100mA Type S were already there, I would certainly leave it there, just to cover the (albeit rare) eventualities such as the OP may currently be experiencing! What would be gained by removing it?

Kind Regards, John

 

[Spark123]

Could be a N-E fault somewhere too, best get an electrician in to check it out.

 

[JohnW2]

As RFL has already mentioned there is no real need for the 100mA unit, but maybe on this occasion, if one or both 30mA units are faulty, it would have offered some form of secondary protection.

I typed a bit too slowly but, as you will see, I've just made that point as well!

Kind Regards, John

 

[EFLImpudence]

Is there an official definition of 'nuisance tripping' as opposed to 'real'?

 

[JohnW2]

Could be a N-E fault somewhere too, best get an electrician in to check it out.

I don't think there's any doubt that the OP needs an electrician. For a start, the RCDs need checking, as does the dishwasher/supply ... and whatever else arises by following one's nose thereafter!

Kind Regards, John

 

[PrenticeBoyofDerry]

I typed a bit too slowly but, as you will see, I've just made that point as well!

Maybe it would be a better solution to have a 30mA time delayed RCD, rather than 100mA unit