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Connecting two earthing systems - PME on both - any implications of this?

Former Community Member
Former Community Member
Question out of theorotical interest, can you connect the earthing systems of two PME supplies to achieve equipotential bonding between the two electrical supoplies or devices they power?


What are the pro's and con's of this? I understand the implications of PEN faults which might make the earth have touch voltage but if there is equipotential bonding between two earth systems would the earth fault current (earth which now carries live voltage from neutral) not flow through to the earth of the other PME supply?


Appreciate your thoughts.
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    Usually requires the DNO's consent.


    Do you have enough information to permit compliance with Regulation 542.1.3.3? How would you propose to size the csa of the cable(s) used to connect the two?


    What happens if one installation at some time in the future becomes out of the control of the person responsible for the other one, and a supply is upgraded?


    Why is this different to bonding of extraneous-conductive-parts? BS 7671 has this covered with the sizing requirements of the main bonding, and the fact that those extraneous-conductive-parts are in contact with the ground, i.e. they are in themselves earth electrodes which help limit the effect of diverted neutral currents. An insulated cable between the two installations would not achieve the same thing.
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  • 0
    Usually requires the DNO's consent.


    Do you have enough information to permit compliance with Regulation 542.1.3.3? How would you propose to size the csa of the cable(s) used to connect the two?


    What happens if one installation at some time in the future becomes out of the control of the person responsible for the other one, and a supply is upgraded?


    Why is this different to bonding of extraneous-conductive-parts? BS 7671 has this covered with the sizing requirements of the main bonding, and the fact that those extraneous-conductive-parts are in contact with the ground, i.e. they are in themselves earth electrodes which help limit the effect of diverted neutral currents. An insulated cable between the two installations would not achieve the same thing.
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