diversity doesn't apply to individual circuits..
it applies to the overall demand of the installation, in this case the house..
you still have to install the cables and breakers to take the maximum load possible.. in this case 52A..
with diversity I can get a 10.4KW cooker on a 20A breaker with 1.5mm² T+E to feed it, but we all know that on sundays and at xmas the breaker won't hold and the cable will melt as the actual max load is 43A...
But all that is taken into account in the required relationship of Ib to In to Iz, and a cable with an Iz of 20 is OK on a breaker with an In of 20.according to the curves in the regs, a B20 breaker will take 40A for about 180 seconds before it blows..
a lot of damage can be done in 3 minutes at twice the rated current..
granted the copper won't melt ( and maybe I should choose my words more carefully in future ) but the insulation won't like it..
311 MAXIMUM DEMAND AND DIVERSITY
311.1 For economic and reliable design, the maximum demand of an installation shall be assessed. In determining the maximum demand of an installation or part thereof, diversity may be taken into account.
433.1.1 The operating characteristics of a device protecting a conductor against overload shall satisfy the following conditions:
(i) The rated current or current setting of the protective device (In) is not less than the design current (Ib) of the circuit, and
(ii) the rated current or current setting of the protective device (In) does not exceed the lowest of the current carrying capacities (Iz) of any of the conductors of the circuit, and
(iii) the current (I2) causing effective operation of the protective device does not exceed 1.45 times the lowest of the current carrying capacities (Iz) of any of the conductors of the circuit.
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