A standard domestic radial light circuit would be on a 6A or 10A MCB and run with 1 twin and earth cable. It would only be on a 32A MCB if the cable was a bigger cross section and it was supporting a larger load like a shower or cooker. Is a radial circuit on 32A breaker a fire risk? - MyBuilder Is this answer helpful?Thanks!Give more feedbackThanks!How can it be improved?How can the answer be improved?Tell us how Radial Circuit | Wiring a Radial Circuit | Electrical Although in almost all situations, certainly domestically, 2 twin and earth will be the wiring choice to go for for sockets circuits, the size of cable will be in some ways be dictated by the size of MCB in the consumer unit that the circuit will run from. For a radial socket circuit, the size of MCB used should be no more than 16 amps.New Wiring and Cable Colours · DIY Projects · Ring Main Cable sizing for radial circuits | Screwfix Community Forum communitywfix››Electricians' TalkNov 08, 2011Cable sizing for radial circuits. Text books talk about radial circuits using 4mm twin and earth, protected by a 32 amp breaker. However it seems to me that as soon as you bury such a cable in the wall, its current carrying capacity drops. If you regard sinking the cable into a plastered wall as reference method A, the current drops to 25 amps.