Commercial premesis

[sparks1234]

In a commercial building that is owned by a landlord and then each office area has its own water supply and distribution board.
The sub-main comes from a panel from the main installation in the basement so the sub-main is a TN-S but main incomer is usually a TNCS.
When form filling you are asked what type of supply at the origin, I take it this means the main incomer where it enters the building, when asked for the Ze, what do you put in? is it a limitation as you cant turn the supply off to disconnect the earth.
As for the bonding, are they enquiring as to the bonding for the main building or your particular zone?

 

[Guest123]

Hi.

When it isn't possible to measure Ze and PFC, then you are permitted to use the value obtained from the DNO by enquiry. For a TN-C-S they'll just tell youit should be less than 0.35 and tell you to calculate PFC from that.

Is there a main water incommer in the basement where the supply is branched off to each unit??? If so then the water should be bonded here back to the MET at the main intake and, point of entry to each unit.

 

[sparks1234]

Hi.

When it isn't possible to measure Ze and PFC, then you are permitted to use the value obtained from the DNO by enquiry. For a TN-C-S they'll just tell youit should be less than 0.35 and tell you to calculate PFC from that.

Is there a main water incommer in the basement where the supply is branched off to each unit??? If so then the water should be bonded here back to the MET at the main intake and, point of entry to each unit.

The water comes into the building and rises up through the risers and spurs off to each office. So I am assuming that you would need to be satisfied that bonds are in place in the basement and at entry to the office to satisfy the cert. Assuming that the pipe to the office is copper not plastic

 

[Guest123]

Agreed, only for the unit you are working on though.

 

[sparks1234]

Cheers Len