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Extra Low Voltage (ELV)

Former Community Member over 4 years ago

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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0 Former Community Member over 4 years ago

Sparkingchip:

Mike M:

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.

I am not sure you have grasped the distinction between the three categories.

The main distinguishing feature is the quality of the insulation used in the transformer and connected equipment. The note to 411.7.1 describes FELV as insufficiently insulated with respect to circuits at higher voltage.

The earthing of ELV equipment is to make up for weaknesses in basic insulation, good quality SELV equipment is sufficiently insulated from circuits at higher voltages and earth.

Now what was your question?

Andy Betteridge

I am not sure you have grasped my question. SELV,PELV,FELV are already very well defined in BS7671:2018. My question was BS7671:2018 is classing cables extra low voltage (ELV) as an operating voltage not exceeding 50Vac or 120V ripple-free dc, 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 ?

If you read BS7671:2018 you will see that FELV does not need to meet the isolation requirements imposed on SELV and PELV.
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0 Former Community Member over 4 years ago

Sparkingchip:

Mike M:

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.

I am not sure you have grasped the distinction between the three categories.

The main distinguishing feature is the quality of the insulation used in the transformer and connected equipment. The note to 411.7.1 describes FELV as insufficiently insulated with respect to circuits at higher voltage.

The earthing of ELV equipment is to make up for weaknesses in basic insulation, good quality SELV equipment is sufficiently insulated from circuits at higher voltages and earth.

Now what was your question?

Andy Betteridge

I am not sure you have grasped my question. SELV,PELV,FELV are already very well defined in BS7671:2018. My question was BS7671:2018 is classing cables extra low voltage (ELV) as an operating voltage not exceeding 50Vac or 120V ripple-free dc, 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 ?

If you read BS7671:2018 you will see that FELV does not need to meet the isolation requirements imposed on SELV and PELV.
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Extra Low Voltage (ELV)

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