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Gas bond in detached garage ?

aligarjon

Hi Guys.

I carried out an EICR earlier and am a little unsure of the bonding setup.  House built in 1982. Original wiring which is ok. 16mm tails/6mm earth. 6mm bonding conductors. 60 amp main fuse.

The gas meter is in the detached garage. About 2 meters from house. There is a 6mm gas bond in there at the gas meter that is clearly under sized as it has been taken from the 2.5mm supply cable for the garage power.

The gas pipe from the meter goes through a 4inch duct and pops up in the kitchen below the units next to the water pipe. Both are bonded there in 6mm. This area backs onto the garage so in reality 2 or 3 meters away if that is relevant. 

My question is is the bond by the gas meter actually required as it is outside anyway or will it potentially need upgrading.

My gut reaction is it is fine as it is. There is no water in the garage.

The supply pipe to the gas meter drops into the concrete floor and as far as I can chip the floor away looks steel, although I am only seeing threading nut connections before it is buried so may well be plastic.

Any guidance would be appreciated

Thanks.  Gary

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  • 0
    mapj1 said:
    Its not dangerous, but it may well not meet the letter of current regs.

    If it's PME, then diverted neutral currents is a possibility. The current is what it is, but with this arrangement, we can end up with voltages developing, so bonding in both places is really necessary ... DNO will be worrying about the bonding size back to the PME earthing terminal to help prevent overheating and control voltages ... I might not go as far as "not dangerous" if it is PME, although the danger will come from outside the installation, for example in the form of a broken PEN conductor.

  • 0 in reply to gkenyon

    My point is that  the gas pipe is the better conductor linking the two locations, by far.  Adding the still relatively high resistance of some 10mm or 16mm2 does not greatly reduce the fraction of the diverted neutral current in the gas pipe from the existing set up where the weedy parallel path includes the CPC of some 2,5mm, nor does it much alter the voltage drop across it or the 2.,5mm cpc.

    Mike.

  • 0 in reply to mapj1

    Agreed in one sense ... in another the additional bonding and remote location increases the chances that diverted neutral currents can lead to dangerous potentials in that installation ... especially if the pipe doesn't make contact with the mass of the earth between the garage and shed (possible if it's in a plastic outer).

  • 0 in reply to gkenyon
    gkenyon said:
    especially if the pipe doesn't make contact with the mass of the earth between the garage and shed (possible if it's in a plastic outer)

    I'll bet my bottom dollar that that pipe is not dry (most of the year).

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