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Bonding District heating Pipework,

Toby Knox

Hi

Everyone's favourite topic Earthing and bonding, Some background information, We have insulated metallic pipes going under ground to several blocks of flats. Each block has an intake room where the pipe work enters from the ground to the energy centre 1 kilometre away. Each block is at a different stage of construction with some being occupied. After spending some time on site I am yet to see any bonding in place for any pipework. I'm aware of the test for extraneous-conductive-part but due to these being occupied the pipework has meters, probes ect which creates parallel paths and the buildings in early construction phase only have temporary power with no reliable MET to test with. 

So many question how can I determine if the existing pipe work requires bonding and how can I test the new pipework with no reliable earth?

Attached is an photo of the intake room pipe work in the early stage of Construction.

Thank-you for any help on the matter.

Parents
  • 0

    So what happens if somebody connects to the pipe in another building?  There's every chance that it could then become earthy in your building, because of what it's connected to in the other.

  • 0 in reply to Simon Barker

    That's probably fine most of the time. The far more serious problem is when a faulty piece of kit in one building makes it 'live' in all the others and then,due to a lack of bonding, or that the resistance is not low enough, the ADS fails to operate.

    The other source of  complication is that if the area covered is large enough to span the supply areas of a few substations, then you are inviting all sorts of excitement in terms of how fault currents and diverted neutral currents find their way home vie other houses wiring.

    Gas installations can have insulating joints to prevent such cases, and unless the heating fluid is especially conductive, there is an argument for a similar approach with plumbing.

    Mike

  • 0 in reply to mapj1

    The NICEIC advises that insulated fittings (couplings) on metallic pipework, especially in older designs, may be challenging to identify without proper tagging or marking. In cases of uncertainty, it is recommended to bond the pipework to the MET of the installation

    -Andrew

  • 0 in reply to AMK

    Which is a reasonable precautionary approach given that most recent installations relied on earthing for ADS, or were so old that it had been given no thought at all when originally installed.
    However, this is a new design, and like plastic gas pipes, there should be no difficulty in identification.

    background.

    https://electrical.theiet.org/media/1189/insulation-inserts-in-metallic-gas-service-pipes-to-consumers-premises.pdf

    M

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