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Extra Low Voltage (ELV)

Former Community Member
Former Community Member
Guys,


BS7671:2018 is classing cables extra low voltage (ELV) as an operating voltage not exceeding 50Vac or 120V ripple-free dc.


BS7671 goes on to further categorize ELV cables into SELV, PELV, FELV.


For single core green/yellow insulated equipotential bonding cables lets say originating from an earth bar and bonding some structural steel work, are these classed as FELV under BS7671:2018 ?
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    SELV circuits don’t require a CPC because the insulation within the transformer and other equipment  is good enough to provide complete separation between the ELV and SELV circuits, so you will not be at risk due to there being 240 volts on the SELV circuit.


    FELV circuits may require a CPC because the insulation within the transformer and other equipment  is not good enough to provide complete separation between the ELV and SELV circuits and there may be 240 volts on the FELV circuit and you are relying on the ELV circuit CPD to provide ADS and the RCD to provide supplementary protection, if there is one, for the FELV circuit.


    So the circuit protective conductor or any other protective conductor has to be capable of withstanding the voltage and current that may be placed on it, which in the case of a FELV circuit is generally 240 volts, even though the circuit is rated at say 24 Vdc.


    I am failing to see how you have strung this topic out for so long, this is stuff we learnt in the second year of  C&G 2360 course.


     Andy Betteridge 

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  • 0
    SELV circuits don’t require a CPC because the insulation within the transformer and other equipment  is good enough to provide complete separation between the ELV and SELV circuits, so you will not be at risk due to there being 240 volts on the SELV circuit.


    FELV circuits may require a CPC because the insulation within the transformer and other equipment  is not good enough to provide complete separation between the ELV and SELV circuits and there may be 240 volts on the FELV circuit and you are relying on the ELV circuit CPD to provide ADS and the RCD to provide supplementary protection, if there is one, for the FELV circuit.


    So the circuit protective conductor or any other protective conductor has to be capable of withstanding the voltage and current that may be placed on it, which in the case of a FELV circuit is generally 240 volts, even though the circuit is rated at say 24 Vdc.


    I am failing to see how you have strung this topic out for so long, this is stuff we learnt in the second year of  C&G 2360 course.


     Andy Betteridge 

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Community Rules & Guidelines