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Bonding

Northern Spark

I need to install bonding to the gas services in a flat above a shop that has two electrical supplies and two gas supplies. The flat was two separate flats that have had a door put in between them, essentially making them one flat. Half of the flat is supplied from a single phase supply and consumer unit located in the flat, the other half is supplied from one phase of the shop's three phase supply, located in the shop. There are two boilers in the flat, one with gas supplied from a meter located in the flat, the other boiler supplied from a gas meter located on an external wall. (I think they have a common water supply, but haven't been able to confirm this yet. There is a 10mm bonding connection to the water supply). I presume this all needs bonding together? I am not sure on the best approach. Can I run a 10mm bond from the consumer unit to the two gas pipes and another from the 3 phase board to both the gas pipes? Or one bonding conductor from the consumer unit, to both the gas pipes, and then to the 3 phase board?

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  • 0
    Northern Spark said:
    The flat was two separate flats that have had a door put in between them, essentially making them one flat.

    Can it remain as two separate installations? If not I foresee some serious re-wiring and "gas plumbing" ?

    We wouldn't want (if that is a risk) PEN faults (or similar) using the two (formerly separate) gas installations as an electrical path for diverted neutral currents or fault currents that are not expected?

    It's not possible to simply bond two electricity supplies together without having a conversation with the DNO. There's a Reg for it (believe it or not) that makes the 'designer' (person who decides to bond them together I guess) responsible: see Regulation 542.1.3.3. At the same time, don't forget Regulation 411.3.1.1 ...

  • 0 in reply to gkenyon

    Both supplies are PME. Diverted neutral currents is a main concern. Doesn't keeping them separate pose the risk of touch voltages above 50V occurring as some of the extraneous parts will not rise in voltage under fault conditions?

  • 0 in reply to Northern Spark
    Northern Spark said:
    Doesn't keeping them separate pose the risk of touch voltages above 50V occurring as some of the extraneous parts will not rise in voltage under fault conditions?

    Yes, quite simply, that is not permitted by Regulation 411.3.1.1

    But because of diverted neutral currents, and Regulation 542.1.3.3, you will need the DNO's permission to bond them, and know how to choose an appropriately sized conductor.

    It may well be that the flat needs to be converted to a single supply, or one or both supplies converting to TT.

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  • 0 in reply to Northern Spark
    Northern Spark said:
    Doesn't keeping them separate pose the risk of touch voltages above 50V occurring as some of the extraneous parts will not rise in voltage under fault conditions?

    Yes, quite simply, that is not permitted by Regulation 411.3.1.1

    But because of diverted neutral currents, and Regulation 542.1.3.3, you will need the DNO's permission to bond them, and know how to choose an appropriately sized conductor.

    It may well be that the flat needs to be converted to a single supply, or one or both supplies converting to TT.

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