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DNO TN-C-S supply to an industrial unit building which contains ATEX zones

Patrick Benson

Hi,

Could anyone offer any advice in relation to the earthing arrangement within ATEX zones please?

If a building (a large steel frame industrial unit) has a DNO TN-C-S supply, could it be acceptable for this earthing arrangement to enter ATEX zones? I'm considering a PEN conductor fault potentially representing an issue which should be avoided.

Is it reasonable to expect the ATEX zones required earthing arrangement to be defined in the project Hazardous Area Classification and DSEAR Risk Assessment and or project performance specification?

I appreciate BS EN 60079-14 may provide appropriate recommendations, which I intend to review a.s.a.p.

(Apologies if the above outline is too brief).

Thank you in advance for any responses.

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  • 0

    Patrick,

    I don't have my copy of BS EN 60079-14 with me at the moment, but I can tell you that the standard does state that where a TN earthing system is used it shall be TN-S with separate protective conductor and neutral in the explosive atmosphere.

    Hope this helps!

  • 0 in reply to Ross C

    Hi Ross,

    Thank you for your response.

    So that's the DNO supply to the building must be TN-S?

    Thanks again.

  • 0 in reply to Patrick Benson
    Patrick Benson said:
    So that's the DNO supply to the building must be TN-S?

    Or TT.

    If the supply to the building is TN-C-S, it cannot become TN-S unless you involve another transformer and make a new earthing system. The reason is that these designations apply to the whole system.

    In a building, typically you can't have more than one earthing system, because Regulation 411.3.1.1 requires that simultaneously-accessible exposed-conductive-parts to be connected to the same earthing system.

  • 0 in reply to gkenyon

    Hi,

    Thank you for your comments, much appreciated.

    So, a TN-C-S building supply earthing arrangement should not be used for the earthing arrangement in ATEX zones.

    I'll have a good read of BS EN 60079-14 a.s.a.p.

    Thanks again.

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  • 0 in reply to gkenyon

    Hi,

    Thank you for your comments, much appreciated.

    So, a TN-C-S building supply earthing arrangement should not be used for the earthing arrangement in ATEX zones.

    I'll have a good read of BS EN 60079-14 a.s.a.p.

    Thanks again.

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