FELV providing both basic protection and fault protection

[John Lundrigan]

Hi All,
Regulation 411.7.1 states that the provisions described for Regulations 411.7.2 and 411.7.3 are applied for a nominal voltage not exceeding 50 V ac or 120 V dc then this combination is known as FELV.

Does that mean then that if and installation is defined as FELV then it IS protected for both basic (direct contact) and fault conditions.

Sorry to write it like this but I want to know if FELV automatically means that both protections.

Thanks

Jonel

 

[Richard Burns]

If the installation meets all the requirements for a FELV system then the installation has both basic and fault protection. Just because it is extra low voltage and earthed does not mean it has both basic and fault protection. It requires the basic insulation, simple separation of the FELV supply and ADS on the supplying circuit. It is not a protective measure in and of itself, the protection is still ADS it is just safer because of the voltage.

However this is the same as saying that a standard radial circuit that has all the requirements for basic and fault protection has basic and fault protection.

 

[John Lundrigan]

Thank you Richard. This is the way I understood it from BS 7671 - If it WAS FELV then it did have both basic and fault protection.

Thanks

 

[John Lundrigan]

So SELV also, by regulation 414.2 also has basic and fault protection as far as I interpret thyese rules?

Jonel

 

[Richard Burns]

SELV is a protective measure in its own right; in that a properly designed SELV system that meets the criteria in the regulations does not pose a (significant) risk of electric shock, either whilst in use or during a fault, i.e. it has both basic and fault protection provided by the SELV installation.

 

[John Lundrigan]

Thanks Richard

 

[John Lundrigan]

So with SELV and FELV it is really the separation element that provides the fault protection, the removal of any return path when touched under fault conditions.