GWC Sparky
Member
Please could I have some opinions of a job I am looking at.
This is a commercial property, with multiple office suits on a 1st floor supplied by individual mains supplies from the DNO. individual meter cupboards at the back of the building supply each office.
One of the office suit supplies are as follows but all are supplied similarly:
The supply service head has a 60A main fuse and 16mm meter tails to the electricity meter and to a Switch Fuse SP+N isolator with 60A cartridge fuse protecting the 16mm squ TW&E sub-main cable that supplies the office suit DB on the 1st floor above the meter cupboard.
The CPC of the sub-main cable is 6mm squ. The Main Earthing Conductor from the service head to the Switch fuse MET is 10mm. in this case but some are 16mm.
The only Extraneous conductive parts that I believe require Main equipotential bonding in this office suit would be the gas central heating system in the kitchen of the office suit. However the gas meter for this boiler is located outside of the this office suit area in a communal toilet area. and is bonded to another office supplies earthing system MET.
My initial feeling is that the CPC of the TW&E cable is undersized for this situation with reference to Table54.7 and Table 54.8, however it could also be proved adequate buy calculation using the Adiabatic equation 543.1.3.
A constructive discussion would be gratefully received, thank you.
This is a commercial property, with multiple office suits on a 1st floor supplied by individual mains supplies from the DNO. individual meter cupboards at the back of the building supply each office.
One of the office suit supplies are as follows but all are supplied similarly:
The supply service head has a 60A main fuse and 16mm meter tails to the electricity meter and to a Switch Fuse SP+N isolator with 60A cartridge fuse protecting the 16mm squ TW&E sub-main cable that supplies the office suit DB on the 1st floor above the meter cupboard.
The CPC of the sub-main cable is 6mm squ. The Main Earthing Conductor from the service head to the Switch fuse MET is 10mm. in this case but some are 16mm.
The only Extraneous conductive parts that I believe require Main equipotential bonding in this office suit would be the gas central heating system in the kitchen of the office suit. However the gas meter for this boiler is located outside of the this office suit area in a communal toilet area. and is bonded to another office supplies earthing system MET.
My initial feeling is that the CPC of the TW&E cable is undersized for this situation with reference to Table54.7 and Table 54.8, however it could also be proved adequate buy calculation using the Adiabatic equation 543.1.3.
A constructive discussion would be gratefully received, thank you.