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Reg 419.2 Applicable to VSD driven motor?

Steven WALKER

Good afternoon,

When using cable design software such as ElectricalOM, there is a check box within the "Earthing" tab / adiabatic check of CPC. It states Provision of  regs 419.2 & 419.3 are applicable. (BS7671)

If checked it will remove the warning regarding the earth fault / disconnection time (should a warning exist with the modelled install)

Can someone confirm with a degree of certainty that the checkbox would reg 419.2 be applicable to a motor supplied from a VSD drive? 

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  • 0

    Is the wiring between the VSD and the pump part of the fixed wiring where perhaps the pump or VSD may be change or bridged out  but the wiring not ?
    This will be something that is case specific.

    In general, if you are sure that the VSD is providing the ADS function, then the normal rules as set by upstream breakers etc do not apply to cables that are in effect protected by the VSD. In such a case, by all means set the software to ignore that accordingly, but there is an onus to confirm instead that the internal current limits / trips within  the VSD do actually keep the potential shock hazards to either a low enough voltage, or a short enough duration, to give an equivalent level of safety.  It is not just a case of 'its a VSD - out of scope no thoughts required' .

    Of course the regs are not that clear, but I'm pretty sure  that is the intent.

    Mike.

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  • 0

    Is the wiring between the VSD and the pump part of the fixed wiring where perhaps the pump or VSD may be change or bridged out  but the wiring not ?
    This will be something that is case specific.

    In general, if you are sure that the VSD is providing the ADS function, then the normal rules as set by upstream breakers etc do not apply to cables that are in effect protected by the VSD. In such a case, by all means set the software to ignore that accordingly, but there is an onus to confirm instead that the internal current limits / trips within  the VSD do actually keep the potential shock hazards to either a low enough voltage, or a short enough duration, to give an equivalent level of safety.  It is not just a case of 'its a VSD - out of scope no thoughts required' .

    Of course the regs are not that clear, but I'm pretty sure  that is the intent.

    Mike.

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