Nuisance tripping when neighbour strims grass

[squarepeg77]

Hi,
I have a problem with nuisance tripping where my consumer unit trips when my neighbour strims her lawn. It doesn't happen every time and doesn't happen when she mows the lawn - only when she uses the strimmer. This has been going on (and off!) for the entire time I've been in the house - almost five years - but now it's got to the point where I really want to get the problem sorted.

At the advice of a neighbour who works for UK Power Networks, I bought her a new strimmer but the problem is still happening. She says she uses the new strimmer, but when I am away for the weekend I have no way to be sure... so I just have to take her word for it. She has had two electricians give her strimmer, RCD and CU the all-clear, but I don't know what tests have been done.

I have a Memera CU with an A100HE RCBO, 100A 30ma. A few years ago I borrowed an earth tester (? I can't remember exactly what it was) from my neighbour and my consumer unit RCBO seemed to operate as expected - tripped when it should, didn't when it shouldn't.

What should I do now? I have not yet had an electrician test any of my installation as from talking to several electicral folks we thought the best guess was that my neighbour's strimmer was putting noise on the ground and that a new strimmer was a likely fix. Well, that hasn't worked!

So what now? Can I just get the RCBO replaced, or do I have to go for a whole new consumer unit?

Cheers,
Jonathan

 

[westie101]

I investigated something similar many years ago, changing the RCD cured it, so you might be on the right track.

 

[EFLImpudence]

If the above is not a solution there could be a fault somewhere that an electrician with test instruments could find.

Meanwhile, just to clarify - is this RCCB (it's not a RCBO) also your main switch and therefore the only RCD in the installation?

Could you provide a picture of your consumer unit for us please?

If you have room perhaps a reconfiguration of the CU could alleviate the situation by sharing the loads with another device.

 

[JohnD]

you have an A100HE which is a 100A 30mA RCD (it is not an RCBO), I will guess it is used as a main switch or perhaps you have a split load.

This is not now considered best practice, as you are likely to have a bit of background leakage from all the appliances and all the circuits in your house (especially watery ones like CH boiler and pump; immersion heater; kettle; washing machine, shower) and although none of these leakages might be much, all of them together may be approachiong the trip current of your RCD, so it takes little extra to trip it.

If you have a modern Memera 2000 or 2000AD CU, it can be fitted with RCBOs, which means each circuit has its own RCD combined with its MCB, so there is no accumulation of leakage from multiple circuits. This can cost a bit though as they are usually about £30 each.

BTW if you have any of your own electrical circuits or metal water pipes outside the house, such as fountain, ground lamps or shed supply, try disconnecting it as this might be interacting with your neighbour's strimmer. Have a look at your installations earthing arrangements, and your neighbours too if you can, and post some pics.

 

[liam2010]

Is your earthing system a TT system an if so oes anyone think it coul be a problem between the two houses earthing systems being linkd

 

[EFLImpudence]

You're getting confused with 100mA RCD. This is 100A 30mA RCD.

 

[bernardgreen]

Is your house semi-detached or terraced with your neighbour's house ?

Where is the socket that the nieghbour uses for the strimmer ?

It might be one that was accidently wired into your installation. ( seen at least two incidents of sockets on party walls wired to cables on the other side of the wall and one was not accidental ).

But more info about the installations ( yours and hers ) is needed.

 

[IJWS15]

Does the strimmer stop when the RCD trips?

 

[bernardgreen]

Does the strimmer stop when the RCD trips?

Good thinking

 

[squarepeg77]

Thanks for all the responses!

The only external wiring I have is for a porch light and a floodlight, but they are wired just through the house walls (no long cable runs). There are no external water pipes.

I live in a cluster home - 3 houses 'stuck' together. The neighbour whose strimming causes the problems is not one of my direct neighbours, but our back gardens are next to each other.

When my consumer unit RCD trips, her strimmer is fine. She uses an internal socket and plugs the strimmer into a normal circuit breaker (which never trips).

My UK Power Networks neighbour told me it was protective multiple earthing system, which is what the big sticker on the company fuse says too.

Pictures attached.

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• squarepeg77
• 10 May 2011
• 1

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• squarepeg77
• 10 May 2011
• 1

 

[JohnW2]

Is your earthing system a TT system an if so oes anyone think it coul be a problem between the two houses earthing systems being linkd

It's very possible for two adjacent properties to have TT electrodes with overlapping resistance areas, particularly in the case of 'narrow' terraced houses. Although this results in some degree of 'linking' of the two earth systems, I really can't see how this could cause an RCD to operate.

Kind Regards, John.

 

[JohnW2]

Where is the socket that the nieghbour uses for the strimmer ?
It might be one that was accidently wired into your installation. ( seen at least two incidents of sockets on party walls wired to cables on the other side of the wall and one was not accidental ).

Indeed - but that, in itself, would presumably not normally result in RCD operation unless the strimmer was faulty, and we're told it happened with two different strimmers.

However, if, somehow, just the neutral (or just the L) had been 'shared' between the 'strimmer socket' and the adjacent property, then that would normally result in the behaviour described.

Kind Regards, John.

 

[JohnW2]

Hi,
I have a problem with nuisance tripping where my consumer unit trips when my neighbour strims her lawn. It doesn't happen every time and doesn't happen when she mows the lawn - only when she uses the strimmer. This has been going on (and off!) for the entire time I've been in the house - almost five years ...

I'm just starting to wonder how strong is the link between the strimming and the tripping...

• How common is it for your RCD to trip when your neighbour uses the strimmer. You say 'not every time', but roughly what proportion of times the strimmer is used - 90%, 50%, 10% or what?
  
  When it happens, does your RCD trip immediately she starts (or stops) strimming, or can it happen 'out of the blue' after she has been strimming for some time?
  
  Does the RCD ever trip when your neighbour is not using the strimmer?

Kind Regards, John.

 

[squarepeg77]

How common is it for your RCD to trip when your neighbour uses the strimmer. You say 'not every time', but roughly what proportion of times the strimmer is used - 90%, 50%, 10% or what?

I'd say there is a 50-75% of my RCD tripping when my neighbour strims the grass.

When it happens, does your RCD trip immediately she starts (or stops) strimming, or can it happen 'out of the blue' after she has been strimming for some time?

I am often away at the weekends, so I am not always able to monitor the situation. I'd say it doesn't trip immediately, but usually happens after a few minutes. Last October when I was actually at home, I remember my RCD tripping three times in about 5 minutes of strimming.

Does the RCD ever trip when your neighbour is not using the strimmer?

No.

 

[bernardgreen]

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• bernardgreen
• 10 May 2011
• 1

Is your consumer unit next to the meter ?

If so where do those wires go to ?

Looking at the incomer. Is it a thick cable with a thinner cable taped to it or is is two cables about the same size ? Could that cable be one of the network neutral earthing bonds to a rod in or close to the house.

Is there is a "deficiency" in the earthing of the neutral in the network ?

If yes then possibly the start up in-rush current of the motor in the strimmer could be bouncing the network neutral above ground and the bounce is affecting your RCD. But it would have to be a large motor to cause enough bounce to trip an RCD.