Confirming earth bonding continuity when cannot isolate supply

[ipf]

If you cannot access to test, use additional notes to explain.

For example:
SUPPLY CHARACTERISTICS AND EARTHING ARRANGEMENTS and PARTICULARS OF INSTALLATION AT THE ORIGIN.
These sections of the certificate have not been fully completed due to the lack of access and lack of information where required.

 

[Amusingold]

If you cannot access to test, use additional notes to explain.

For example:
SUPPLY CHARACTERISTICS AND EARTHING ARRANGEMENTS and PARTICULARS OF INSTALLATION AT THE ORIGIN.
These sections of the certificate have not been fully completed due to the lack of access and lack of information where required.

Good point thanks, but this wouldnt be acceptable on an initial verification, but yes could add a bit of detail on how supply characteristics ze pfc etc are enquired due to unable to isolate, I dont think zero value and a limitation would cut it wouldnt feel right claiming satisfactory without at least an enquired value for ze and pfc, and earthing tick boxes satisfied with visual, past test certs and annual service of transformers I feel is bags of proof of good earths.

Thank you everyone interesting and informative and backed up my thoughts and testing processes going forward. Good to hear everyones take on these certain scenarios they dont go into detail or cover at all in the classroom!

Peace !

 

[ipf]

Good point thanks, but this wouldnt be acceptable on an initial verification, but yes could add a bit of detail on how supply characteristics ze pfc etc are enquired due to unable to isolate, I dont think zero value and a limitation would cut it wouldnt feel right claiming satisfactory without at least an enquired value for ze and pfc, and earthing tick boxes satisfied with visual, past test certs and annual service of transformers I feel is bags of proof of good earths.

Thank you everyone interesting and informative and backed up my thoughts and testing processes going forward. Good to hear everyones take on these certain scenarios they dont go into detail or cover at all in the classroom!

Peace !

I'm talking along the lines of industrial or large commercial, really. You can only test what you CAN test, though, no matter what the installation.
I must admit, I have never done the example in a domestic situation. There's generally a way round it. If you cant get a Ze, at least you can get Zs at db and explain that in notes.

 

[loz2754]

The initial verification you are doing is only for the additional circuit you have installed, not the whole installation. Therefore, in my opinion, as long as the Zs at the DB it's installed from is ok and the R1+R2 etc are ok then you have done what is reasonably practicable to ensure ADS is met. With a note on the certificate to explain this.

 

[loz2754]

@ipf Why the dislike if you don't mind me asking?

 

[Amusingold]

The initial verification you are doing is only for the additional circuit you have installed, not the whole installation. Therefore, in my opinion, as long as the Zs at the DB it's installed from is ok and the R1+R2 etc are ok then you have done what is reasonably practicable to ensure ADS is met. With a note on the certificate to explain this.

Yes I accept that as good enough to tick the earthing boxes, but as for ze and pfc at origin if I couldnt isolate I would enquire, as putting as zs
at db value in as ze would be wrong in my eyes.

Again thanks for everyones input! Much appreciated guys

 

[loz2754]

Yes I accept that as good enough to tick the earthing boxes, but as for ze and pfc at origin if I couldnt isolate I would enquire, as putting as zs
at db value in as ze would be wrong in my eyes.

Again thanks for everyones input! Much appreciated guys

I'm not suggesting putting a Zs at DB in as Ze. That would indeed be incorrect. All I'm saying is that if your new circuit is fed from a sub DB, and it is impracticable to disconnect the earthing conductor at the origin, then you use the enquiry method for the Ze, measure Zs at the sub DB, also at the end of your new circuit. That is all you can do.

 

[loz2754]

Yes all this is correct , so I would have thought visual would be fine for earth connection tick box, and ze and pfc just put down enquired values? Or would you feel comfortable writing a zs at sub main value in the ze section? As enquiry is acceptable for ze and pfc I think I would just put enquired values, but obviously safe in the knowledge we have good earths from visual and like you say previous install test results. You have confirmed in similar thinking to me and dont think theres any other way around it. Thanks for everyones input!

PFC is measured with the earth conductor connected.

 

[Amusingold]

I'm not suggesting putting a Zs at DB in as Ze. That would indeed be incorrect. All I'm saying is that if your new circuit is fed from a sub DB, and it is impracticable to disconnect the earthing conductor at the origin, then you use the enquiry method for the Ze, measure Zs at the sub DB, also at the end of your new circuit. That is all you can do.

Ahh yes to satisfy the main earth conductor tick box, yes, totally agree, apologies, good to hear everyones opinion, like I said earlier they don't traxh these real world scenarios at in the class room! And even when the questions are raised the tutors seem to shrug them off as they have no real on the job experience!

Thanks again

 

[i=p/u]

Ahh yes to satisfy the main earth conductor tick box, yes, totally agree, apologies, good to hear everyones opinion, like I said earlier they don't traxh these real world scenarios at in the class room! And even when the questions are raised the tutors seem to shrug them off as they have no real on the job experience!

Thanks again

not like classroom. Ul find some meters willl give you same reading for zdb and ze, deoending on distance apart. Or even less. i.e
Ze =0.32.
Zdb 0.31

 

[pc1966]

Sadly none of the MFT do 4-wire Kelvin style measurements for Zs/PFC, so uncertainty of several 0.01R is just part of the game depending on just where and how hard the probes are in contact.

Only the very expensive high current loop testers do that it seems. It is a shame no MFT even offer it as an extra cost feature as I would have been happy to shell out and extra £50-100 for some Kelvin style crocodile leads (where each jaw has a separate cable, and one per clip is the test current and the other is observing the dolt drop, eleiminating the test cable's effect).

 

[ipf]

@ipf Why the dislike if you don't mind me asking?

Sorry mate. Complete accident and just seen........wiped. I see we can, that's good.?

As well....some of my comments in this thread are a bit over the top.......I didn't notice that the OP was talking MWC. My fault.?

 

[loz2754]

Sorry mate. Complete accident and just seen........wiped. I see we can, that's good.?

As well....some of my comments in this thread are a bit over the top.......I didn't notice that the OP was talking MWC. My fault.?

Cheers bud?