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Thread: Switch chassis earth

  1. #1
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    Switch chassis earth

    Hi all
    Your thoughts on the below questions would be appreciated
    This is an older installation maybe 30 years

    Question one
    I have a house that is wired so that all the steel boxes mounted in walls for switches are earthed with a lug and screw not bolted.The earth readings are fine.Is this in order or do I have to replace all screws with bolts .I have been taught earth must be bolted.The earth connection via screw is tight.

    Question two
    The switch chassis is not earthed.So when I loosen the switch off the box the switch chassi is not earthed .The box is the box mentioned in question 1 earthed with lug and screw. Should the switch chassis be earthed.The switch chassis does not have a earth terminal.All.parts are steel.

    Question three

    In the ceiling I have light boxes separated from the conduit that should be connected to the light boxes .With the result that the light circuit single core cables are exposed for about 15 mm.I am not sure there is any regs that disallows this under open wiring the 6.4.5. Or under 6.5 wireways.

    Thanks


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  2. #2
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    Hi Gtfast
    Question one
    I would say page 179 6.12 Earthing
    Note 2 the requirements for earthing arrangements are intended to provide a connection to earth that
    a) is reliable and suitable for the protective and functional requirements of the installation.
    b) can carry earth fault currents, protective conductor currents and leakage currents to earth with out danger from thermal , thermomechanical and electromechanical stresses and from electric shock that arise from these currents, and
    c) where relevant, is also suitable for functional requirements.
    yes i would say it is correct, as for being the best way to earth no.

    Question two
    I would say the switch chassis will be earthed through the screws that secure the cover to the chassis, when the cover is on. so when the cover is in place and the screws secured it is earthed. i would say that is fine so long as you get a acceptable reading back to the earth in the D/B, for the Resistance of earth continuity conductor test.

    Question three
    As for this one i would say the guy who did the job did not measure correctly, i would use a pvc coupling and ensure the conduit is connected to the light boxes, just going to take time to repair each light box. Would not leave the wires exposed.
    This one just comes down to poor workmanship.

    cheers
    Melvin

  3. Thanks given for this post:

    Gtfast (31-Mar-17)

  4. #3
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    Thank you .
    Melvin


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