Determining Ze at a sub CCU in a flat in a converted house

[zap]

Scenario: PME supply. House converted into flats. Main distribution board splits into five sub boards, one for each flat. Each flat has its own meter and CCU fed by twin and earth. The water pipes in each flat are bonded. (Water pipes are jointed by threaded horse-hair joints). There are no gas services.
Question: Can I or how do I obtain Ze at a flat's CCU assuming main services are bonded at the main distribution board (i.e. parallel paths).

 

[telectrix]

measure as normal at each flat's CU and record as Zdb. if you want a Ze, this must be taken at the main DB.

 

[zap]

Many thanks telectrix, can Zdb then be used to calculate Zs? i.e. Zs = Zdb + (R1 + R2)

 

[Chr!s]

Scenario: PME supply. House converted into flats. Main distribution board splits into five sub boards, one for each flat. Each flat has its own meter and CCU fed by twin and earth. The water pipes in each flat are bonded. (Water pipes are jointed by threaded horse-hair joints). There are no gas services.
Question: Can I or how do I obtain Ze at a flat's CCU assuming main services are bonded at the main distribution board (i.e. parallel paths).

When you do a Ze test on a terraced inevitably you will be measuring all the services connected in parallel on the distribution.

I would treat them as a electrical installation and use Ze.

Regards Chris

 

[telectrix]

you may find that the Zdb is not accurate as parallel paths may exist due to water bonding at main DB, i would calculate the Zs from Zdb and compare with an actual Zs reading, easily taken at a socket outlet. if you are unable to access the main DB and isolate it at source, there's not much more you can do. if it's a PIR you are doing, LIM or N/V will have to go in any boxes you can't get a reading for.

 

[zap]

Thanks for that telectrix, yes, I am going through the motions of a PIR as a practice. I will then compare my report(s) and certification with the 'real' ones when they are available. I understood your post and the logic makes sense so thanks again.
Thanks also to all other contributors...

 

[shovelhead]

Thanks for the post telectrix - I've just encountered exactly the same problem.