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AMD 4 DPC - new section 545 - functional earthing

AJJewsbury

Has anyone had a look at the proposed new section 545 (functional earthing) in AMD 4 DPC?

At first glance, it seems rather confusing (to little heads like mine at least). I can see the general point of trying to keep protective conductor currents (whether due to normal conditions or faults) from flowing along functional earthing conductors - so AFARP connect to the protective earthing system at one point only - at least for each "cluster" of interconnected equipment.  It seems to be rather prescriptive though - e.g. "If there are multiple functional bonding conductors present in the electrical installation, a separate main functional earthing terminal (MFET) shall be installed for ease of connection for these conductors. The main functional earthing terminal shall be connected to the main earthing terminal only once." - so if I had two clusters of equipment at opposite ends of a large installation, would this prevent me connecting each cluster independently to a local PE (say a nearby DB) but rather have to run all the functional earthing/bonding conductors back to one central MFET? It doesn't seem to be a good fit with the proposed 545.2 "The main functional earthing terminal MFET and the MET may be combined" nor the methods described in 444 (e.g. Fig A444.2).

Or have I missed something obvious? (again)....

   - Andy.

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  • Hi Andy. In my view, running all functional earthing conductors back to a central MFET could be more cumbersome and costly in most instances. The existing method in Figure A444.2, seems much easier to apply and clearer than the proposed methods in section 545.

    -Andrew

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  • Hi Andy. In my view, running all functional earthing conductors back to a central MFET could be more cumbersome and costly in most instances. The existing method in Figure A444.2, seems much easier to apply and clearer than the proposed methods in section 545.

    -Andrew

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