Strange fault, some clarification needed..

[Lectrician]

Aren't you in effect doing a L-N impedance check of the supply when doing a Ze check anyway? The only difference is the meter tail vs the earthing conductor however the neutral meter tail shouldn't cause much voltage to be apparent on the MET.

If PME, i guess you could confuse matters by saying that, yes.

You want to measure a loop between the live and CNE conductor in the head - with NOTHING else connected. Remove earths from the service head (or the CU), and switch off the main switch so all you have is the L and the CNE. Check to see what the impedance is, and if it is stable.

Does that sound better?

If you get an OK reading, it could just be that pipework is providing a return path which is slightly lower than the neutral, and so current decides it may as well flow that way too.....The very reason why PME is not allowed in petrol stations - network circulating currents in the metal storage tanks and pipework is not good!

 

[Spark123]

The only difference I can see is a few pieces of wire, not that much that they will make any difference.
The Ze test is conducted with the installation isolated and the earthing conductor in isolation hence I'd expect to give similar results.

 

[Lectrician]

Whatever - but you are testing the loop externally between the L and CNE - who cares about the little bit of earth? Just make sure it is disconnected, I say from the head as you then know for sure there is parallel paths.

Make sure the L and N are also isolated.

Wheres the argument?

 

[Spark123]

I'm not arguing, just trying to understand the reasoning for doing a L-N loop when he has already done a Ze

 

[Lectrician]

Because I bet he did it with the main switch on for a start. And a very good chance he didn't disconnect the earth - many people are lazy.

 

[Spark123]

I hope not, but you can't help people who take short cuts like that. Given though his Zs reading was lower than his Ze which rings true with it being done in isolation.

 

[flyingsparks]

Because I bet he did it with the main switch on for a start. And a very good chance he didn't disconnect the earth - many people are lazy.

ACTUALLY... I did it with the main switch off and the main earth disconnected!!!! I do know how to do a Ze you know!!