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Bonding of external tray support systems

Stuart Urban

I came across the below scenario and wondered what everyone thought of it.

An industrial site with multiple layers of tray running horizontally over external open ground. Different trays contain power and communications cables. Power cables are armoured. The tray and horizontal supports are bonded back to the MET, however, the metal vertical stanchions of the tray support system are not bonded but are electrically isolated from the tray work (by plastic washers) - I'm told this is a requirement of the communications engineer.  The stanchions are fixed to a concrete base.

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  • Not really possible to comment without seeing the installation. Noting that extraneous-conductive-parts only require bonding to conform to BS 7671 in buildings. In some circumstances, there may be safety and/or lightning protection implications ... and without further information, it's not possible to understand whether the communications engineer has considered those in their design.

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  • Not really possible to comment without seeing the installation. Noting that extraneous-conductive-parts only require bonding to conform to BS 7671 in buildings. In some circumstances, there may be safety and/or lightning protection implications ... and without further information, it's not possible to understand whether the communications engineer has considered those in their design.

Children
  • in reply to gkenyon

    Can you please explain the ref to "safety" in your response?

  • in reply to KDY
    KDY said:
    Can you please explain the ref to "safety" in your response?

    Circulating currents, causing heating, or EMC issues.

    What does the 'comms' do? In some installations, comms is essential for safety, and EMC becomes a safety issue.

    Without knowing more about the installation, it's like asking a question without a definitive answer.

    Could also be to prevent corrosion of the supports or their fixings due to various frequencies of "noise" on the earthing system ... or even DC.

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