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Undersized Main Earth Conductor

Former Community Member
Former Community Member
Hi Folks,

I was carrying out an EICR on a domestic property with a PME supply.

The Main earth conductor is 10mm, the water and gas bonding is also 10mm connected to the earth terminal in the consumer unit.

Would you give this a C3 or C2?


I know there's an equation knocking about for checking main earth conductors however, I'm under the impression that this only works if the bonding conductors are terminated at the MET and not the consumer unit.


Any suggestions will be welcome.


Thanks
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    Using Table 54.7 is fine but if the earthing conductor is a smaller CSA than 54.7 requires then you need to do the calculation in accordance with Regulation 543.1.3 which will highly likely come up with a smaller CSA.


    However if the installation is PME Regulation 542.3.1 requires the earthing conductor to have a minimum CSA in accordance with Table 54.8.



    So a 10mm Earthing Conductor in this case is probably going to meet the requirements of BS 7671 but you must do the adiabatic equation to verify it.
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  • 0
    Using Table 54.7 is fine but if the earthing conductor is a smaller CSA than 54.7 requires then you need to do the calculation in accordance with Regulation 543.1.3 which will highly likely come up with a smaller CSA.


    However if the installation is PME Regulation 542.3.1 requires the earthing conductor to have a minimum CSA in accordance with Table 54.8.



    So a 10mm Earthing Conductor in this case is probably going to meet the requirements of BS 7671 but you must do the adiabatic equation to verify it.
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