unable to measure Ze!

mini-si · Mar 8, 2011

Hi all, we are currently carrying out PIR's on resisdental properties/flats, but only the common areas,landlord supplies.My problem is that today i came across a landlords supply which share its supply with lots of flats and for various reasons i was unable to turn off supply, disconnect main earth and carry out Ze test. So my question is: for page three(main characteristics) do i just write lim down for Ze and PFC or maximum values? i.e for TNC-S 0.35ohms unsure of max PFC? kind regards simon

adslev · Mar 8, 2011

Enquiry is another option, by ringing the energy provider and asking them! PFC should be tested live so ......

Sintra · Mar 8, 2011

PFC can still be measured as the main bonds and earth are connected for this test. As for the Ze on a PIR that i could not isolate i would test with earth connected and note on cert that Zdb has been taken as Ze.

mini-si · Mar 8, 2011

okay no problem will take the measurement from landlords db as i cant pull main fuse to test pfc as im aware the main bonding/earth should be left connected due to parallel paths/worst case.

mart8235 · Mar 8, 2011

PIR certs have a very useful limitations section on the front page.
As long as you can reasonably justify your limitations, i.e. 'unable to test for Ze as not safe to remove main earth', then just put LIM in relevant box.

I often find that when I carry out a PIR in an occupied unit/property you just cant go disconnecting supplies, or isolate server circuits, or remove sensitive equipment to enable an IR test. there's always something stopping you carrying out all the tests, so you just go for a LIM and justify it. just don't take the ****!

IQ Electrical · Mar 8, 2011

mini-si said:
okay no problem will take the measurement from landlords db as i cant pull main fuse to test pfc as im aware the main bonding/earth should be left connected due to parallel paths/worst case.

Yes, I'd prefer to see a value in the Ze box and an explanation that the value was measured with all bonding etc. in place due to resident constraints.

Why would you 'pull the main fuse' to do PFC?