Have a major problem

[Octopus]

Ok. This is based on real fault finding.

Rcd tripping. Socket circuit was the cause. A nail had clipped the live core, the damp , very newly plastered wall was allowing a path to the metal back box which was connected to earth. Disconnect earth to back box and rcd would hold.

The nail was about 9 inches from the back box.

 

[westward10]

As I said a metal back box may provide a return for the wet plaster but we have no idea if metal back boxes in the OPs case are employed.

 

[Ian1981]

I’ve had a low insulation resistance reading between live and earth on a new build however it’s between the mains fed switch (permanent live in) and the metal back box buried in block work wall.
A reading of 1.75Mohms and that’s when all cpcs are removed from the back box and I’m just testing between live at the switch and an un earthed back box.
Oh and there’s no earthing conductor connected to the source as no meter fitted.

 

[james stas]

 

[james stas]

he says its going back to the substation and bypassing the rcd, he metered the wall to a nearby socket earth and got 177 volts. says all readings were above 299 megohms. he got really nasy when i asked for a report and said how insulting it was. im a terrible human for nearly killing people and now i question his honesty and integrity. i only asked for a report in a polite manner

 

[james stas]

this is all with a brand new board. so it is possible to fit a light, test, leave and the whole wall is live?

 

[westward10]

I think you have to accept some kind of joint responsibility. He didn't fit the capping correctly, you refitted it damaging the cable. Should his testing have picked up the fault well you will not know unless you recreate the circumstances at the time.

 

[james stas]

my nail was making the capping live i am told and there was no imbalance between neutral and live because it was going back to the substation.,,....

 

[Ian1981]

That is a strange cable brown, blue and black conductors.

It’s grey man not blue and your a spark

 

[westward10]

It’s grey man not blue and your a spark

I know I took a closer look and deleted it