Eddie asks this question about an electrical supply and earthing system to a metallic shed. It has been answered by the ECA (Theme - Distribution Equipment including Cable Management):
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Question: I need to install a three-phase supply to a large metal shed sized 20 x 10m.
The house supply is three-phase, 100A, and E.ON has installed new meterage and a three-phase isolator?. The earthing system is TNC-S.
The shed will have its own three-phase board, and I will install the earth rod and bond to the metalwork. I also intend to install an 80A three-phase MCB after the main isolator? - then to connect to SWA cable. The board in the shed will have a100mA RCD.
Is this arrangement acceptable?
Answer: As the shed is made of metal, I would recommend separating the TNC-S earth from the supply and earth the shed using a TT arrangement and RCD.
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