BS 7671 Section 521.8.3

Moesebnew: 
 

Section 521.8.3 of BS7671 states: Where two or more circuits are terminated in a single junction box this shall comply with BS EN 60670-22. My question is what if several circuits will terminate in a single wiring device back box which are usually  manufactured to comply with   BS EN 60670-1.

BS 7671 doesn't define “junction box”.

Given the definition of circuit, however, we might conclude that it must be possible to terminate two circuits into one accessory fitted to an accessory backbox not complying with BS EN 60670-22, otherwise it would be impossible to use a fused connection unit to supply a fused spur as shown in the diagrams of Appendix 15 of BS 7671.

Reasoning: There are strictly two circuits present … the incoming supply circuit, say 32 A ring final circuit or 20 A radial circuit, and the outgoing spur with lower cross-sectional area conductors. The spur must be a different circuit (as defined in Part 2 of BS 7671, because it is not protected by the same overcurrent by the same protective device as the supply circuit .

Moesebnew: 
 

Section 521.8.3 of BS7671 states: Where two or more circuits are terminated in a single junction box this shall comply with BS EN 60670-22. My question is what if several circuits will terminate in a single wiring device back box which are usually  manufactured to comply with   BS EN 60670-1.

BS 7671 doesn't define “junction box”.

Given the definition of circuit, however, we might conclude that it must be possible to terminate two circuits into one accessory fitted to an accessory backbox not complying with BS EN 60670-22, otherwise it would be impossible to use a fused connection unit to supply a fused spur as shown in the diagrams of Appendix 15 of BS 7671.

Reasoning: There are strictly two circuits present … the incoming supply circuit, say 32 A ring final circuit or 20 A radial circuit, and the outgoing spur with lower cross-sectional area conductors. The spur must be a different circuit (as defined in Part 2 of BS 7671, because it is not protected by the same overcurrent by the same protective device as the supply circuit .