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RCDs for both Fault & Additional Protection

PG
BS7671 states for Additional Protection [415.1.2] - "The use of RCDs is not recognised as a sole means of protection and does not obviate the need to apply one of the protective measures specified in Sections 411 to 414." - These methods being methods of protection against shock - ADS, Double Insulation, Separation & SELV/PELV.


531.3.6 states " - - - - - - -RCD - - --  - - -may provide fault protection and additional protection simultaneously."


This appears to be inconsistent. Is 531.3.6 meant to apply to only one type of neutral  earthing system?


Regards

Parents
  • 0
    It is trying, and perhaps not very clearly, to say that an RCD can be used to detect a fault current in the CPC, i.e. first fault is live to the correctly earthed case of some equipment, the RCD provides ADS. You only get  short duration shock, if you are unlucky enough to be touching it at the time the fault comes on.


    It should NOT be used to justify omitting that CPC, where the RCD relies on some poor b***** getting a shock to trip it, as when the fault comes on it keeps working with a live case and nothing trips until then.

    It may come as a surprise to UK readers who have not traveled outside the reach or IEC based rules,  but in some parts of the world such RCD and no earth installations are seen as OK - a sort of Class 0 + RCD.

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  • 0
    It is trying, and perhaps not very clearly, to say that an RCD can be used to detect a fault current in the CPC, i.e. first fault is live to the correctly earthed case of some equipment, the RCD provides ADS. You only get  short duration shock, if you are unlucky enough to be touching it at the time the fault comes on.


    It should NOT be used to justify omitting that CPC, where the RCD relies on some poor b***** getting a shock to trip it, as when the fault comes on it keeps working with a live case and nothing trips until then.

    It may come as a surprise to UK readers who have not traveled outside the reach or IEC based rules,  but in some parts of the world such RCD and no earth installations are seen as OK - a sort of Class 0 + RCD.

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