Neutral to earth fault - lighting circuit

[daveb]

Hi folks,

so here was a new one I came across today. Was sent to put in a new bathroom fan today to an old Barrats house. Opened up the switch at the bathroom door to have a look - no neutrals. Ok I thought, neutrals obviously looped at the ceiling roses. Wanting to test the circuit first, I wanted to find out which neutral was feeding the circuit as they weren't in order. To cut a long story short, I removed every single neutral (bar the incomer) from the neutral bar, and the lights stayed on! After calling another spark, he recommends pulling the main earth and low and behold - the lights went off.

What are everyone's thoughts on this, and have you come across this before? Crossed neutral somewhere or have they used a cpc as a neutral somewhere along the line?

The house had an octopus box for the lights which I have never seen before, and never want to see again!

The fault was recorded on the test sheet and have advised that customer that they should have this looked at. A new feed was run to the bathroom light switch off of another lighting circuit through a local RCD. The faulty circuit is a shambles from the previous owner and have told the customer they may be quicker and cheaper having someone to quote for the affected rooms to be rewired.

Look forward to your responses.

 

[westward10]

Seen it lots on commercial premises, neutral is normally pinched to the conduit/trunking system.

 

[Octopus]

Hi folks,

so here was a new one I came across today. Was sent to put in a new bathroom fan today to an old Barrats house. Opened up the switch at the bathroom door to have a look - no neutrals. Ok I thought, neutrals obviously looped at the ceiling roses. Wanting to test the circuit first, I wanted to find out which neutral was feeding the circuit as they weren't in order. To cut a long story short, I removed every single neutral (bar the incomer) from the neutral bar, and the lights stayed on! After calling another spark, he recommends pulling the main earth and low and behold - the lights went off.

What are everyone's thoughts on this, and have you come across this before? Crossed neutral somewhere or have they used a cpc as a neutral somewhere along the line?

The house had an octopus box for the lights which I have never seen before, and never want to see again!

The fault was recorded on the test sheet and have advised that customer that they should have this looked at. A new feed was run to the bathroom light switch off of another lighting circuit through a local RCD. The faulty circuit is a shambles from the previous owner and have told the customer they may be quicker and cheaper having someone to quote for the affected rooms to be rewired.

Look forward to your responses.

I would start looking for a N-E fault - seen this before and had to track down the fault to sort it out too. Interesting stuff if you have the time and patience to do it.

every day is a learning day.

 

[davesparks]

I cannot believe I have just read that!
You disconnected every neutral conductor from the neutral bar and energised the installation, and then disconnected the earthing conductor and energised the installation!

Are you actively trying to kill someone?


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[daveb]

I cannot believe I have just read that!
You disconnected every neutral conductor from the neutral bar and energised the installation, and then disconnected the earthing conductor and energised the installation!

Are you actively trying to kill someone?


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Theres always at least one person on these forums that is the first to pick faults to make themselves look like the best, most amazing electrician. These people should try and remember they weren't on the job nor understand how things were done.

 

[davesparks]

Theres always at least one person on these forums that is the first to pick faults to make themselves look like the best, most amazing electrician. These people should try and remember they weren't on the job nor understand how things were done.

I wasn't there, nor did I see how it was done. But disconnecting the earthing conductor of a live installation, or energising an installation after disconnecting the earthing conductor is incredibly dangerous and downright stupid regardless.

 

[daveb]

I wasn't there, nor did I see how it was done. But disconnecting the earthing conductor of a live installation, or energising an installation after disconnecting the earthing conductor is incredibly dangerous and downright stupid regardless.

when all you have is an electrician in the house, at the mains board momentarily pulling the earth before reconnecting. Yes, that's downright dangerous and stupid. Comments like this help no one except make you look down right arrogant mate. Thanks but no thanks to those kinds of comments

 

[westward10]

Yeah it wasn't the best thing to do, by having the neutrals disconnected it could only have been following the earth path, maybe best not to listen to your sparky mate, but hey ho no one died, did they! Live and learn as Murdoch says.

 

[davesparks]

when all you have is an electrician in the house, at the mains board momentarily pulling the earth before reconnecting. Yes, that's downright dangerous and stupid. Comments like this help no one except make you look down right arrogant mate. Thanks but no thanks to those kinds of comments

It doesn't matter who is, or is not in the house, everything which is earthed or bonded within the house will have become live with reference to earth.
I don't care what you think of me, just stop placing your life at risk unnecessarily.

You knew that a N-E fault existed thanks to the previous test results, so why the hell didn't you investigate this using a normal and safe testing method? Why was it necessary to place yourself in danger?

 

[tomspark93]

Had this once on a dormer bungalow, it was an absolute nightmare to find but the neutral to a lighting circuit loop had been broken And one end had shorted to the CPC. So the lights were still on when I turned off the mcb.

 

[westward10]

Chill out Dave we have all done dumb things, he won't do it again.

 

[daveb]

Had this once on a dormer bungalow, it was an absolute nightmare to find but the neutral to a lighting circuit loop had been broken And one end had shorted to the CPC. So the lights were still on when I turned off the mcb.

That does sound like a nightmare indeed. It's difficult for us as our company specialises in kitchens and bathrooms so all we can do is advise if we cannot solve the problem. To rectify faults, our customers are probably charged a premium compared to firms out there who are just electricians. I would like to get in there to try and find the problem on my own, but you then worry that customers think you've placed the fault there to try and get extra work.


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[mattg4321]

Are you a kitchen fitter or exclusively an electrician who happens to work for a kitchen/bathroom firm?

Just a bit worrying that you don't mention any testing usual conventional methods eg. IR testing.

Why would you think the circuit should be rewired without properly testing first when it's most likely a simple n-e fault?

 

[SJD]

I once found the N and E crossed in a fluorescent light fitting while doing an EICR (so half the lighting circuit was using the CPC for N).

 

[daveb]

Are you a kitchen fitter or exclusively an electrician who happens to work for a kitchen/bathroom firm?

Just a bit worrying that you don't mention any testing usual conventional methods eg. IR testing.

Why would you think the circuit should be rewired without properly testing first when it's most likely a simple n-e fault?

Haha, no I'm not a kitchen fitter but the latter that you mention. I think it's safe to say that it is a N-E fault.

Re the rewire, it's a small bungalow that for some reason is split on two light circuits. The "bad" circuit is only doing the bedroom and kitchen hence the reason it would take little time to rewire these two rooms.




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[tomspark93]

Unfortunately that was a similar scenario for me. It was a kitchen refurb and the customer just didn't want to know. It just reinforces the fact that the first thing you should do is test the circuit before you work on it.

 

[Lucien Nunes]

Lifting the earth was a Very Bad Test (tm) for two reasons.

1: It's dangerous. Not only all the appliances and metalwork and everything in the house becomes live via the fault, but if there are any extraneous parts outside the house in contact with any circuit's CPC (water pipes connected via the boiler, shared service mains etc) then they could become live too and endanger someone in another property.

2: It's not guaranteed to give the right result: E.g. if the C/H system has metallic contact to an incoming water main your lighting load will still work, with the current returning to earth through the main. So you're no further forward with your testing. But a simple IR test would find it for certain, and without the danger.

IMHO it's like searching for a gas leak with a match.

 

[Sparkie30]

IMHO it's like searching for a gas leak with a match.

witnessed that aswell but with a blow torch. Could not believe it.

 

[davesparks]

Chill out Dave we have all done dumb things, he won't do it again.

How do you know he won't do it again? I won't be chilling out about a person placing their own, and other peoples, lives in danger any time soon.

 

[mattg4321]

To be fair, he should know. He's just spent all day and 6 pages arguing a point he's clearly wrong about! Doubt he'll make that mistake again.