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]

When you say the IR test confirms the earth issue do you mean you got a low reading phase/neutral cores to armour? If there is a low reading to the armouring that would suggest damage to the cable somewhere and I dont see that you can energise without sorting it.

EDIT...Sorry just noted you are getting the voltage on a core....still shouldnt happen if the core is isolated at both ends....sugests a damaged cable which again I wouldnt energise.

 

[Sav]

Hi wirepuller and thanks for the reply.

When you say the IR test confirms the earth issue do you mean you got a low reading phase/neutral cores to armour? If there is a low reading to the armouring that would suggest damage to the cable somewhere and I dont see that you can energise without sorting it.

EDIT...Sorry just noted you are getting the voltage on a core....still shouldnt happen if the core is isolated at both ends....sugests a damaged cable which again I wouldnt energise.

But as line to neutral ok, faulty earth islolated and new 16mm earth run, surely this is ok.

R1 + R2 checked on swa and ok, all tests carried out at consumer end and all ok. Another sparks I spoke to , who is a friend, said all is ok and he will call Elecsa tomorrow to confirm but should be fine.

Like I said, if I could run a new swa I would, but as its a terraced house, floors finished, there is no safe or good route.

Thanks again guys
Sav

 

[Deleted member 9648]

Is there a low IR to the armour or just the core used as an earth?

 

[Sav]

Is there a low IR to the armour or just the core used as an earth?

Just the core, the armour is fine ( thank god) !!!

Thanks wirepuller for helping out,

Sav

 

[Deleted member 9648]

Should be ok then....bit of a worry though.....just make sure you note that it was installed by others on the cert.

 

[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

 

[Deleted member 9648]

Could be but Sav says the IR to the armouring is ok which would kinda make that unlikely....seems strange tho that only an internal core is affected.

 

[Sav]

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

Hi Pennywise,
Thats the 1st thing I checked on both ends and all ok.

Best regards,
Sav

 

[cornburn]

Yes surely if there's only 40V showing up it's a nick somewhere, and is 99% likely to be at one end or the other at the terminations or where it was stripped? Probably worth pulling apart first to check as that would be easier to sort?

 

[pevvers]

This may be a silly question, but is the armour connected to earth sufficiently at the supply? You could be seeing an induced voltage on it if it's not connected....

 

[Sav]

This may be a silly question, but is the armour connected to earth sufficiently at the supply? You could be seeing an induced voltage on it if it's not connected....

Hi Pevvers,
Sorry for the late reply, I hope your not sleeping as could you explain this further. Reason is I am sure that I saw an earth not connected to the met (TN-S supply by the way).

Its a mess down there and space is limited. Is it possible that if the earth core was only terminated inside the metal clad isolator and then not connected again to the met, that an induced voltage could happen ???

Sav

 

[Deleted member 9648]

You did say in OP that there were IR issues though which would suggest damage of some kind.....

 

[pevvers]

You did say in OP that there were IR issues though which would suggest damage of some kind.....

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.

To the OP, from what points was the 40V measured from? Armour and third core, MET and third core?

To be honest, it sounds like a dodgy installation by a dodgy sparks, so nothing can be ruled out. What one of you guys would say "I can't connect it as it's got 40V IN the earth"? 40V still sounds like induced voltage to me....

 

[pevvers]

Is it possible that if the earth core was only terminated inside the metal clad isolator and then not connected again to the met, that an induced voltage could happen ???

It's very possible that this could be the case. I originally read it as the armour had the voltage on it, as this is normal practice for sparks who think that because it's not being used as a CPC it doesn't need to be connected to earth, and then you will find induced voltages, and get little belts off of them. But if it's the third core and it's not connected to earth, the same could happen.