On 08/11/17 22:00, pamela wrote:

36A is a lot. Wouldn't that melt the insulation on the wires?


No. The current carrying capacity of a cable is determined by (mostly)
how hot it gets.

A ring final circuit is designed to run forever at 32A with a max of 20A
in any part of the cabling.

This is based on PVC cable having a max operating temp of 70C.

In practise:

1) A few degrees over won't do much;

2) There's loads of padding built into the numbers;

3) If you overload a cable to say twice its rating and the MCB takes say
15-20 minutes to trip, the cable has not instantlo y heated up to
beyond 70C - it's gradually overheating and the Type B curve is designed
to reflect that.