Questions about a shared supply. A fault next door trips my ELCB.

[Katie Okeeffe]

The semi-detached house next to mine is being refurbished, including rewiring work. Our electricity meters, fuseboxes etc are back-to-back on the party wall. My ELCB has tripped a few times recently, and I eventually realised that it happens when someone is working next door. Last time it happened I went next door and spoke to a guy fitting pipes for a shower. We established that the ELCB had tripped next door too, and some circuits were off, however he still had some lights on, which must be fed from a different supply.

Is this a normal situation? Should a fault in the neighbouring property trip my ELCB? Is there a possibility that I am paying for some of their electricity?!?! I was told that the recent electrical work next door had been carried out by a competent electrician, who had tested and signed off the installation. But I also understand that the people carrying out the work on the house are friends of the house owner, doing favours for one another, so perhaps they are being a little lax about the formalities.

Thanks in advance for any light you can shed on this situation.

 

[Deleted member 26818]

ELCBs work by detecting voltage on the earth conductor (I believe around 6V).
As your earth conductor is most likely connected through bonding and metal pipework to next door's, any voltage on next door's will also be detected on your ELCB.
By rights, the workers next door, should not be working in a manner that could endanger anyone, or put anyone at risk.
It would appear that they are doing so, if what they are doing is causeing your ELCB to trip.
It may be an idea to contact the Health and Safety Executive and the Local Authority Building Control, to report your concerns.

 

[Marvo]

Is this a normal situation?

No.

Should a fault in the neighbouring property trip my ELCB?

There are unlikely scenarios where a fault on one property could cause the RCD (ELCB) next door to trip but the answer is basically 'No'.

Is there a possibility that I am paying for some of their electricity?!?!

Yes it's possible.

I was told that the recent electrical work next door had been carried out by a competent electrician, who had tested and signed off the installation. But I also understand that the people carrying out the work on the house are friends of the house owner, doing favours for one another, so perhaps they are being a little lax about the formalities.

Their electrician should have completed a full range of tests and highlighted any problems. It's possible he didn't complete all the tests or even that he 'did them a favour' but it's quite unlikely especially as you made inquiries about issues whilst he was there so I'm sure he would have realised it would be risky to do this.

It's not the kind of problem you or a friend can investigate properly. I would get a fully qualified and experienced electrician to come around and just do the appropriate tests for you. It could save you a lot of money in the long run and it will be peace of mind.

I'm sure if you give your location one of the experienced members here will be happy to oblige.

 

[Knobhead]

Is it an ELEC or RCD? If it is an ELCB it should be changed as they are potentially dangerous.

 

[Deleted member 26818]

Is it an ELEC or RCD? If it is an ELCB it should be changed as they are potentially dangerous.

We don't know what the earthing system is.

 

[Katie Okeeffe]

Their electrician should have completed a full range of tests and highlighted any problems. It's possible he didn't complete all the tests or even that he 'did them a favour' but it's quite unlikely especially as you made inquiries about issues whilst he was there so I'm sure he would have realised it would be risky to do this.

It's not the kind of problem you or a friend can investigate properly. I would get a fully qualified and experienced electrician to come around and just do the appropriate tests for you. It could save you a lot of money in the long run and it will be peace of mind.

I'm sure if you give your location one of the experienced members here will be happy to oblige.

Thank you Marvo. Just to keep the facts straight, the person I spoke to was not the electrician who did the wiring, and he told me that the electrician had already completed the tests.

 

[Katie Okeeffe]

Is it an ELEC or RCD? If it is an ELCB it should be changed as they are potentially dangerous.

It is marked as an ELCB. Tripping current 30 mA. Is this really the type you think is dangerous?

 

[Knobhead]

If it’s marked at 30mA it will be fairly recent one. Some from the 60’s and before were dodgy.

 

[oldtimer]

Other things to look out for is shared earths how so well I did a job for a guy and found he had no main earth but when I tested the fuseboard he had an earth hows that well it was a semi and next door had an earth and both houses had a mains earth on the Gas and water supplies so in effect he had a borrowed earth as for could next door be tapped in to your electrics easy switch your fuseboard off and ask next door if the have lost any power

 

[Katie Okeeffe]

Thanks Oldtimer. I think the chances that the old lady who used to live next door intentionally tapped into our supply are virtually zero, and she has sold/given the house to her daughter and son-in-law, and I don't think they would do something like that either. So I'm thinking it's probably a shared earth that is causing a problem.

I have tripped my ELCB myself a couple of times over the years, I wonder if next door's power went off then.

 

[Spazz]

Katie
It might not have been the old lady - it might have been a problem since they built the house. Instead of putting a separate earth for your house and next door they use the same earth connection purely to save time.

Like has been said get a qualified Electrician or post your location on here and Im sure someone will be happy to help.

 

[Katie Okeeffe]

Yes, thanks Nicholas, I understand that, I was making a distinction between the old lady next door nicking our electricity (unlikely), and the problem you describe where we share an earth (pretty likely).

Would the shared earth set-up be permitted nowadays? Given that the electrician has been doing a lot of rewiring next door, and is said to have certified the installation? I mean, could he properly certify an installation with a shared earth?

 

[Rockingit]

There are hardly any scenarios at a domestic level where a shared earth would be recommended, and as others have said it could potentially be dangerous.

It is however possible that the electrician testing the work in your neighbours may not have been aware, it depends on what type of supply is made to the houses from the energy suppliers ('grid') and how much looking with his eyes he did.

Don't anyone get me wrong - I'm not excusing the error, just saying that I can see how it could happen. Do a board change, see a TT wire in the cupboard, see one outside on a rod, do a Ze and get a reading......carry on.....

 

[monkeyhanger]

I recently tested an installation in a terraced house where the earth rod of the house I was testing and next doors earth rod were in pots outside vertually touching each other. When I was doing RCD tests the scumbag from next door banged on the window complaining that I must have turned his electric off. I had a quick look in and he had a voltage operated ELCB which had tripped. I reset it and sure enough it tripped again when I carried on tests.

When I was leaving the property this neighbour followed me to the van claiming that he was going to find out who I worked for etc. as he was claiming for the contents of his freezer and he'd lost work on his computer. Aren't some people nice.

Anyway I moved the rod as part of remedial works later. Problem solved, though maybe I should have left it where it was.

 

[oldtimer]

The shared earth scenario is more common than we thought I did a job for a customer who did not have an earth the DNO put one in for a charge but my customer ended up giving the guy downstairs an earth .

Also here is a better example