measuring zs in a multiple occupancy

[bearlyable]

I am to upgrade a shower circuit from 32amp to 40ampand am just checking the test procedure! The location is a private flat in a large house of four private flats, to measure ze I will have to turn the power off to all flats. my question is 'is there any other acceptable way of getting a ze figure without measuring in this way?....I hope this makes sense?

 

[acat]

I think Im reading you correctly (had a bad hair day myself) why not do a Ze + (R1+R2) to get your Zs or has my bad hair day just got worse.


Chris

 

[bearlyable]

I haven't got any hair for such a day and I wrote 'zs' meaning 'ze', so you hadn't missunderstood, Im just a muppet everyday so I have now corrected my question and can only apologise for the confusion that I hope I have corrected and thank you for your attention so far....Cheers

 

[calv68]

i take it all the flats are ran of a 3 phase board with one meter you could do your ze reading from the board in the flat and call it zdb if the result is acceptable just mark it down on your comments

 

[Davey101]

+1 to calv. We used to have this a lot when working in shops, offices etc. Its not possible to turn off the mains, so it isnt possible to dissconnect the main Earth. We just measured the earth loop and psc at the origin (or as close as we could get), and made a note on the test sheet that we could not dissconect the main earth. We still called it Ze though. I've heard a lot of lads on this forum call it Zdb, never heard of this myself, but it seems like a good idea.

Try to get as close to the mains as possible for your test's (not that it will make much difference) and do a visual inspection to at least make sure the earthing etc looks ok. You'll also have to note that continuity checks on the main earthing conductors and checks on overcurrent protective devices are visual only.

 

[bearlyable]

Re: measuring ze in a multiple occupancy

Thanks chaps 'zdb' can anyone expand on this? and regarding the supply yes its three phase and it goes to four meters but the earth is shared for all supplies.

 

[lj.l]

ZE is at the origin or as close to it as possible,
Zdb is at sub board fed from the main supply or panel board, although its still acceptable to call it ZE.
Thats my take on it anyway

 

[bearlyable]

I was partially under the impression that the ze test was not only to verify results but also to confirm the existence of an earth connection from the supplier??

 

[Spudnik]

It is and one could argue that everything is earthed via bonding and parrallel paths.

I personally would want to do a Ze at the origin.

 

[lj.l]

ZE is the external earth from the supplier or spike.
my post should have been ZS is the same as Zdb ,my mistake I've had a few.
Its Zdb on the the certificate for that db and Zs on the certificate for the panel suppyling that db.
ie.when you record the results for the cable suppling db1 on the panel boad cert its Zs ,when you come to record the results for db1 on a cert its Zdb at the top of the page.
It doesnt really matter what you call it ,its the same reading.