Richie asks this question, which is about fixed equipment on a ring final circuit in student accommodation. It has been answered by the NICEIC (Theme – Distribution Equipment including Cable Management):
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Question: Having recently taken over the design of a student accommodation, I've noticed that the ring final circuits within the studios supply a combination oven / grill / microwave (which has a maximum load of 14A), as well as general sockets and ventilation.
Because of the load of the combination unit exceeding 13A, this cannot be connected to the ring circuit via a fused connection unit and will be connected via a 20A isolator.
I’m aware that Appendix 15 Fig. 15A - Ring final circuit arrangements, Regulation 433.1.204 advises: "The load in any part of the circuit should be unlikely to exceed for long periods the current carrying capacity of the cable. This can be achieved by: (iii) connecting cookers, ovens and hobs with a rated power exceeding 2kW on their own dedicated radial circuit".
However, if we carry out an assessment of the likely load at all parts of the ring circuit, and establish that the current-carrying capacity of the cable will not be exceeded, can you please advise whether you foresee any problem with us proceeding with installing the combination unit on the ring circuit?
Answer: The current in any particular leg of a ring final circuit may not always be equal because of the load placement on the circuit.
It is always advisable to have the heaviest loaded appliances as near as practical to the mid-point of the ring final circuit. As you have already noted, Regulation 433.1.204 takes this into consideration.
Provided that your circuit ‘under its intended conditions of use, the load current in any part of the circuit is unlikely to exceed for long periods the current capacity of the cable’, the circuit is deemed to meet the requirements of 433.1.1.
Appendix 15(informative) takes this into consideration to meet compliance with 433.1.1. However, as the appendices are informative, the final configuration of the ring final circuit is the responsibility of the designer of the circuit.
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