180volts on CPC

[JD Hogg]

Hi All,

I have just been checking out an installation in a 1970's house in prep for a CU change tomorrow, I noticed in one of the light switches the CPC has 180 volts to earth and 60 volts to live on it, obviously it is not earthed. Anyone any ideas what could cause this? Cheers

 

[Knobhead]

Try using an analogue meter to measure it. If it’s still high it’s not just a CU change.

 

[nickblake]

could well be an open circuit on the neutral back feeding down to the cutout fuse and back up the earth , that voltage is what you could get with this fault , it could well be induced voltage on a cpc that has not been connected ,what earthing arrangment is it TNCS TNS TT

 

[trev]

180+60=240. No problem.

 

[Octopus]

Hi All,

I have just been checking out an installation in a 1970's house in prep for a CU change tomorrow, I noticed in one of the light switches the CPC has 180 volts to earth and 60 volts to live on it, obviously it is not earthed. Anyone any ideas what could cause this? Cheers

Do you know this for sure?

 

[JD Hogg]

It's a TNCS system. I do know for sure that this particular CPC is not earthed it's about 4 M ohms to earth. It's just the one switch/CPC, everything else is fine.

 

[Octopus]

It's a TNCS system. I do know for sure that this particular CPC is not earthed it's about 4 M ohms to earth. It's just the one switch/CPC, everything else is fine.

Are you using a metrel tester. Mine can give "odd" results on T&E if the CPC isn't connected.

 

[nickblake]

it does sound like induced voltage to me , see if you can earth it properly that should cure the problem

 

[i=p/u]

start with your r1 and r2

 

[JD Hogg]

Yep I am thinking induced voltage as well so I will check this out tomorrow

 

[JD Hogg]

Just s a follow up to this. I changed the CU today and there is a fault on the downstairs lighting circuit N - E is 1.1 ohms, L - E and L - N is clear. So I've got a bit of fault finding to do tomorrow.

 

[i=p/u]

check link.....

 

[JD Hogg]

what link would that be?

 

[Farmelectrics]

Isolate circuit and see if you can trace cable