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Using a UPS on mobile equipment

Andy May

Hi,

I have a client who requires the electrical installation to run a series of computers inside a fitted out van. The functional specification has stated the use of a UPS to feed the consumer unit. The supply to the van is via an on site plug and socket back the premises supply. My questions is how should I go about ensuring there is a path to earth for the protective devices if the connection to the site supply is lost (disconnected or cut through)?

Andy.

  • 0

    Section 717 may assist or confuse, and it has illustrations about Mobile or Transportable Units.

    Z.

  • 0

    Number of options, including IT or separated systems.

    If going for TN-S then the earth fault loop isn't an issue as it'll be all copper within the van. Often the vehicle chassis can be used as the 'Earth' reference.

    Small UPSs often don't have the 'ommph' to drive ADS - the output voltage collapsing before conventional protective devices can open anyway. The UPS manufacturer may have some advise.

      - Andy.

  • 0 in reply to AJJewsbury
    AJJewsbury said:
    Small UPSs often don't have the 'ommph' to drive ADS - the output voltage collapsing before conventional protective devices can open anyway. The UPS manufacturer may have some advise.

    If relying on 'voltage collapse' instead of traditional protective devices (Regulation 419.2), the UPS manufacturer will have to provide a method for the installer to conduct initial verification that the system is working, and any limitations on (R1+R2) values downstream of the UPS.

  • 0

    As I see it there are two distinct problems.

    1) The supply from which power is taken is poorly defined and may be off earth or reverse polarity, or indeed may fail completely without notice.

    2) The UPS may be designed to run all the time so that the mains is just filling the batteries, or only cut in when external supply fails.

    How many hours must the UPS work for. We have used mains conditioning modules in such cases that are in effect continuous running inverters but the batteries are only good for an hour or so.

    How big a load is all the kit in the van, and is the inverter NE bonded ?

    Mike.

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