Minor works - Zdb & R1R2 tests

[tomodo]

Hi all, when completing a minor works there are two tests that i am unsure the best way to go about, example extension of circuit and new lighting point installed. Fed from industrial 3P board unable to isolate due to plant running. Do not wish to open live board even just for testing purposes for safety reasons. ( don't want to be putting hands in there with single insulated cables etc and some board are very old )

All other tests can be completed its just the Zdb and R1R2

1. Could Zdb be took from enquiry ( a recent ECIR ) ?
2. Can R1R2 be calculated from ZS minus ZDB? Leave a note measuring r1r2 on just the new length of cable installed only as this can be completed dead.
3. Tick box on part 2 - Presence of adequate main protective conductor? - Is the only way to tick this to remove the cover and visually check?

Would this be acceptable?

 

[westward10]

1. No.
2. No because you haven't done 1.
3. Main protective conductor is your earthing conductor at source.

 

[tomodo]

Thanks for the reply if a zdb test were to be measured would it then be acceptable to do point 2?