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.

 

[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.