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Thread: IEC 60079.14 - Electrical Isolation Requirements

  1. #1
    Join Date
    Mar 2018

    IEC 60079.14 - Electrical Isolation Requirements

    Hi All,

    Would like to hear everyone's interpretation on the requirements for Electrical Isolation in IEC 60079.14 clause 8.2 which require that means for isolation shall be provided for all circuit conductors, including the neutral. My understanding of the requirement to isolate all conductors is to reduce the probability of an incendive spark occuring inside the area due to cases like common neutral wiring and potential rise in the earthed circuit conductors.

    1) For instrumentation supplied via PELV supply, i.e. earthed 0V ELV supply:

    a) Do you provide disconnect terminals for each conductor in the instrument loop? including 24V and 0V?, do you provide a 2 pole breaker on the load side of the DC power supply, or even a 2 pole breaker for each instrument?

    b) Do you also isolate earth conductors? For example, if an earth conductor was disconnected from an appliance, and simultaneously an earth fault occurred near the point where the earth conductor was bonded, this could create a spark at the end of the cable inside the hazardous area.

    2) For low voltage supplies:

    a) Do you provide means to isolate earth conductors for LV supplies for the same reason as item 1) b) above? Switching the earth conductor for an AC circuit would be against the wiring regulations where I am from.


  2. #2
    Join Date
    Apr 2004
    Mission Viejo, CA
    I note that you posited your question in another forum. That forum draws from a broader range of IEC experience than this one. We tend to operate within the bounds of US domestic (NEC) practices.

    With the exception of fuel dispensing facilities [See NEC Section 514.11], the NEC has no general requirement for disconnection or isolating grounded (earthed) current carrying, circuit conductors in Hazardous (Classified) Locations (or anywhere else for that matter). Conductors used for grounding (earthing) or bonding that do not carry current during normal operation are generally prohibited from being interrupted or isolated.
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

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