Domestic 2 phase system and additional single phase supply.

Hi everyone, a domestic refurb has an existing 2phase supply. The DNO cut-out is arranged like a standard PME system. Is it reasonable to use the same earth terminal for both phases. I guess this is the same as what would be standard for a 3phase system, only in this instance 2phases. Additionally our client has applied for another single phase supply that is to enter site at another location, therefore 2 supplies onto one site. The DNO seem happy with this though I find it unusual as commercial projects do not seem to like two PME supplies onto one site?

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  • Thank for the reply Sparkingchip,

    We've not checked the voltage across the two phases yet, when we do I'll let you know.

    Whilst the service head supply side of the ISU has 2 phases, the current building is wired on one phase. 

    We will need the second phase for the additional load.

    We originally advised to make a new 3phase application, though have been advised there is no 3phase available on the local network for 200m, which would involve high costs for new connection, civils costs and navigating local streams / becks.

    Steve

  • We originally advised to make a new 3phase application, though have been advised there is no 3phase available on the local network for 200m, which would involve high costs for new connection, civils costs and navigating local streams / becks.

    Seems most likely you have a split-phase setup then (460/230V).

      - Andy.

  • likely you have a split-phase setup then (460/230V).

    I agree, and if that is so you will need to either install 2 single phase consumer units for 230V, or convince yourself that one intended for 3 phase 230/400 is in fact no risk at all with 460v between phases .
    In practice it will always be fine but not all designs are actually rated for split phase  by their makers. The phase to phase PSSC is slightly higher than the equivalent phase to phase on 3 phase for the same single phase loop test readings.

    Mike.