ZE on a factory

[loz2754]

I did find this nugget in the Unite Electricians Guide to Inspection and Testing on page 74, Ze on existing installations; "On periodic inspections it is not necessary to disconnect the main earthing conductor whilst this test is performed". Presumably because you're mainly looking to confirm the presence of a reasonably low earth connection at the origin of the installation, be it TN or TT.

I do not agree with this. Perhaps Unite could have worded it more like "it's not always practicable to disconnect the main earthing conductor".
Wherever it IS practicable to do so, it should be disconnected for the Ze test. I have come across several installations that have somehow lost the connection to the suppliers earth, and the Ze reading was perfectly fine with the earthing conductor connected (due to parallel bonding connections). In fact I had one only yesterday. An upstairs flat that takes it's supply from a common service head in the downstairs flat. An electrician had done some work in the downstairs flat and had disconnected the earthing conductor for the upstairs flat for some reason. I had to reconnect it.
Of course I realise domestic is usually much simpler, and switching off the supply to conduct a proper Ze test is usually straightforward. But my point is, that the Unite statement is implying that it is ok on every periodic inspection to leave it connected. Hmm...

 

[Csparky]

Well I persisted with getting information from the job. Went back today and finally got hold of an indate EICR with the supply details on. Happy days.

Thanks for the suggestions and help.

 

[westward10]

Not sure I would rely on an old Report there are no assurances it is correct.