First proper test and inspect today. Confusion.

[067256]

Hi there,
Done a fuseboard change today, but getting a bit confused with the Ze and Zs tests
Where are these tests done? At the DB main tails incomer, at the origin (sweated earth on incoming cable)
It is a TN-S supply and i have a 3 lead L-N-E megger loop tester.
Getting a bit confused aswell with what bonding is disconnected too.
Any help would be appreciated. Thanks.

 

[Guest123]

Do you have a copy of GN3 or the OSG???

 

[067256]

awaiting OSG from amazon...due to balls up from my college.

 

[trev]

The installation should not be energised till all tests are completed but just in case, Turn off, prove dead, disconnect main earth hook that up to your earth croc. Put neutral probe on neutral terminal and live probe on live then press the button the result given is Ze.
Zs is done at each point of utilisation in a similar manner with the highest reading being the one you record.

 

[067256]

on the certifiacte it says Ze at origin which you have explained.
then it says on the test results page zs at db....is this a different test.

 

[Farmelectrics]

Ze is done at db your zs is your live test at sockets light fittings etc

 

[nickblake]

YEs this is a test of the circuit loop impedance which is carried out at the last point of the circuit or the mid point of the ring it is also carried out after the r1r2 test which on a lighting / radial circuit should be carried out at every point to confirm polarity at each point

 

[trev]

Zs at a db is referred to as Zdb. Only applies when there are submains

 

[Edd]

is the db at the origin of the insulation? sometimes the DB can be at a diffrent point to the incoming service, this is probbely what its asking.

 

[067256]

thanks guys....that really helps me out.

 

[GLENNSPARK]

dont forget here as well 067256......that you will need to test twice for a single phase supply.....once for line-earth...a Ze..this will give you your PEFC at the origin of supply...and another for line-neutral...this will give you your PSC at the origin of supply and it is the HIGHEST of these two measurements that will be your PFC that you record......

 

[mhar]

Don't 3 lead mft's do both tests at once and only display the highest reading? Mine does but don't know about the megger. OP said he was doing a 3 lead test.