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461.2

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If an external high level air-con unit has a rotary isolator positioned next to it, is it good practice to wire the isolator so that it disconnects both L. and N. of the supply?

Z.

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    (b) possibly will be maintained by someone who may be accessing from outside the building (i.e. outside the influence of the main bonding) - and the risk of a potential difference between N and Earth (rather than PE / MET) is greater. The risk is

    So on TN, especially PME, systems, if we're isolating the N, should we be isolating the PE conductor too?

       - Andy.

  • 0 in reply to AJJewsbury

    plug and socket then if you want that, nothing like a 3ft contact gap.

    Mike

  • 0 in reply to AJJewsbury
    AJJewsbury said:
    So on TN, especially PME, systems, if we're isolating the N, should we be isolating the PE conductor too?

    I think that's another debate all together, although there are precedents of access equipment being bonded for various reasons, especially scaffolding.

    It's far more likely in many installations there will be a voltage on a Neutral conductor if the rest of the installation remains live - yes there's a chance of a voltage difference with PME .. and any other earthing system for that matter.

    Just a thought that removing PE on equipment in a system like HVAC might make things worse for you by removing a parallel path for current, because there may be fortuitous earthing via other means (pipework etc.)

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  • 0 in reply to AJJewsbury
    AJJewsbury said:
    So on TN, especially PME, systems, if we're isolating the N, should we be isolating the PE conductor too?

    I think that's another debate all together, although there are precedents of access equipment being bonded for various reasons, especially scaffolding.

    It's far more likely in many installations there will be a voltage on a Neutral conductor if the rest of the installation remains live - yes there's a chance of a voltage difference with PME .. and any other earthing system for that matter.

    Just a thought that removing PE on equipment in a system like HVAC might make things worse for you by removing a parallel path for current, because there may be fortuitous earthing via other means (pipework etc.)

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