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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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    Mike M:



    I would say the single core green/yellow insulated equipotential bonding cables are generally considered safe to tough if disconnected at one end as they still provide basic protection as they are insulated but we are getting a bit side tracked here.


     



    Definitely not getting sidetracked - this is a safety concern. I was talking protective conductors in general - for example, if you disconnect a cpc of a circuit supplying, say, a washing machine from the DB, you might receive a perception-level shock sourced from the noise filter.


    However, the same holds true of bonding conductors. Disconnect a bonding cable in some installations, and you might have possibly even Amperes of current flowing through it - parallel paths - again sourced from LV.


    Telecomms engineers have occasionally been seriously hurt disconnecting bonding conductors. I was also shown many years ago an article from the far east on a particular case of a telcoms engineer who was killed by removing a bonding conductor whilst carrying out a repair - the recommended approach being to "croc-clip" across it.


    Granted in a small installation, such as a dwelling, this may well not be as big an issue, but I would really want to avoid removing bonding conductors if at all possible.


    Your premise of the conductor being insulated does not, unfortunately, hold - simply because the terminal or bare end of the wire is not insulated.

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    Mike M:



    I would say the single core green/yellow insulated equipotential bonding cables are generally considered safe to tough if disconnected at one end as they still provide basic protection as they are insulated but we are getting a bit side tracked here.


     



    Definitely not getting sidetracked - this is a safety concern. I was talking protective conductors in general - for example, if you disconnect a cpc of a circuit supplying, say, a washing machine from the DB, you might receive a perception-level shock sourced from the noise filter.


    However, the same holds true of bonding conductors. Disconnect a bonding cable in some installations, and you might have possibly even Amperes of current flowing through it - parallel paths - again sourced from LV.


    Telecomms engineers have occasionally been seriously hurt disconnecting bonding conductors. I was also shown many years ago an article from the far east on a particular case of a telcoms engineer who was killed by removing a bonding conductor whilst carrying out a repair - the recommended approach being to "croc-clip" across it.


    Granted in a small installation, such as a dwelling, this may well not be as big an issue, but I would really want to avoid removing bonding conductors if at all possible.


    Your premise of the conductor being insulated does not, unfortunately, hold - simply because the terminal or bare end of the wire is not insulated.

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