APPENDIX 15: Ring and Radial Final Circuit Arrangements, Regulation 433.1 (505) Flashcards
The load current in any part of a ring circuit should be unlikely to exceed for long
periods the current capacity of the cable, this can be achieved by (Appendix 15 p.505)
a) Locating sockets to provide reasonable sharing of the load around the ring
b) Supplying immersion heaters etc from the ring circuit near to the distribution board.
c) Connecting cooking appliances with a rated power exceeding 2Kw
d) Limited number of unfused spurs
a) Locating sockets to provide reasonable sharing of the load around the ring
Appendix 15, p.505
Fig 15A - Ring final circuit arrangements, Regulation 433.1.204
The load current in any part of the circuit should be unlikely to exceed for long periods the current-carrying capacity of the cable (Regulation 433.1.204 refers). This can generally be achieved by:
i) locating socket-outlets to provide reasonable sharing of the load around the ring
(ii) not supplying immersion heaters, comprehensive electric space heating or loads of a similar profile from the ring circuit
(iii) connecting cookers, ovens and hobs with a rated power exceeding 2 kW on their own dedicated radial circuit
(iv) taking account of the total floor area being served. (Historically, a limit of 100 m2 has been adopted.)
Unfused spur
An unfused spur should feed one single or one twin socket outlet only. An unfused spur may be connected to the origin of the circuit in the distribution board.
Spur using an Fused Connection Unit not connected directly to the ring. The number of sockets-outlets supplied from a fused connection unit is dependent upon the load characteristics, having taken diversity into account.
Spur using an Fused Connection Unit connected directly to the ring. The number of sockets-outlets supplied from a fused connection unit is dependent upon the load characteristics, having taken diversity into account.
Cables should, wherever practicable, be fixed in position such that they will not be covered by thermal insulation. Where a cable is partially or completely covered by thermal insulation, reference should be made to (523.9 p.153)
Fused connection unit (FCU) to BS-1363-4 Maximum fuse 13-A
Junction Box to BS EN 60670-22.
Junction boxes with screw terminals must be accessible for inspection, testing & maintenance or, alternately, use maintenance-free terminals/connections (526.3 p. 145-146)
Note Conductor sizes relate to BS 6004 ‘flat twin & earth’ cable and the minimum cross-sectional area for the live conductors on i.e. L&N. Reduced circuit protective conductor (CPC) size is permitted i.e. Live = 2.5 mm2, CPC = 1.5 mm2, Live = 1.5 mm2, CPC = 1.0 mm2
