Earth in swa has 40v !!!!

[Sav]

Hi everyone and a happy Easter to you all.

Got a call today to install a consumer unit for a customer into their brand new garage.

They had an electrician who run a swa from an isolator to the new garage board, but could not finish the job as "the earth has voltage guv and its illegal to connect up". Thats what he told the lady.

He has now gone out of business and is abroad ( so he told them).

Anyway, I checked the earth and true there is 40v present at the earth. I did insulation resistance which also confirmed the earth issue.

The thing is, the floor is now tiled over and flooring laid in the hallway ( the isloator is in a small kind of cellar, not very deep though ). I have run a 16mm earth from the isolator (just about got it through behind kitchen units but no way can you get swa there at all), along the garden wall, its in plastic conduit now and into the consumer unit. ZS,R1+R2 ok on the swa and also PFC and ZE ok from the consumer unit as well as sockets and lights (complete test carried out) .

Is this ok in your view, or is there anything else that I must or should do. ??? Even though all looks ok, I have left the isolator off and removed the fuse until feedback from you guys.

Setup is as follows:

60amp d/pole isolator BS1361
16mm swa
original 16mm earth now is safely terminated into a block with brown tape and a note in front of isolator explaining situation (same at consumer unit).

Thanks and regards,
Sav

 

[Deleted member 9648]

But I can't understand how only 40V is being shown at it. If it was an insulation fault I would think it would show the whole voltage, or nothing at all.

Depends on the actual resistance....remember a zero ohms reading on a 500v IR test can still be a fairly high resistance.
I would only expect an induced voltage on a VERY long run of swa....unlikey in a domestic situation.

 

[pevvers]

Depends on the actual resistance....remember a zero ohms reading on a 500v IR test can still be a fairly high resistance.
I would only expect an induced voltage on a VERY long run of swa....unlikey in a domestic situation.

But if the earth is floating, then you can get all sorts of odd readings. I've seen it readings before of 70 odd volts in domestic lighting where there has been a break in the CPC due to dodgy DIY work.... Just one more thing to look for and check really.

Still can't see how only 40V would be showing on it, and also would like to know where this voltage is referenced from....

 

[Deleted member 9648]

'tis an odd one pevvers.....as a new separate cpc has been installed and tested ok I guess we will never know.

 

[UNG]

Had similar thing many years ago and turned out the meter being used was a cheap digital meter with a low ohms/volt and didn't load the circuit sufficiently to pull down the voltage present

When all else fails there is no substitute for the old analogue meter for resolving problems

 

[Sav]

Hi guys,
sorry for the late reply.
IT WAS INDUCED VOLTAGE !!!!

There must of been 3 or 4 earths lying around!! So i started right from the begining with just the swa not connected at either end.
Basically, I stripped everything back, put new glands with banjos, re-earthed the swa correctly both ends, removed my additional 16mm earth, put in a new 60amp isolator (previous one looked rusty and gruby). Now all is ok, finally.

Like I said its a small cellar and I suspect the previous "sparks" just wanted out rather than do things properly.

The other earths were just clipped along a joist and hanging loose at the far end of the cellar, I crawlled and pulled them out.

I learnt a valuble lesson....Dont try to finish off someone else's crap work, start from the begining, take your time and above all ......ASK THE GUYS AT THE FORUM FOR HELP AND ADVICE !!!!

Thank you guys for all your help with this,
Sav

 

[Deleted member 9648]

Well done pevvers who was correct all along,
What happened about the low IR to the core though Sav?

 

[Sav]

Well done pevvers who was correct all along,
What happened about the low IR to the core though Sav?

Hi wirepuller

The earth core had nicks in it which you could only see properly once the gland was removed.

I'm just glad its sorted out and thanks again for yours and everyones help and advice.

The customer didn't really want to pay the extra charge that I charged them due to having to sort the mess out, as they understandably feel cheated by the first "sparks".

But once I explained to them what he had done and what I had to do to sort it out they paid me.

Rightly so I say,
Sav

 

[pennywise]

So it isn't a problem with where the last guy has terminated the armored badly and scored the cores and they are touching the gland ? seems a little strange for and armored to get pranged in a domestic, but hay anythings possible right

Have I got a shout for the guess

 

[Sav]

big shout to pennywise
​

 

[pennywise]

Nice one, good job on finding it

 

[pevvers]

IT WAS INDUCED VOLTAGE !!!!

Glad I could be of help,

But I think that everyone helped in their own way, the great joy about forums,