Following a report from a well respected Contributor here, I've been tasked with sorting out a few problems in a house.
One of them is a good lesson in diversity for cooking appliances.
A 45 amp circuit breaker, 6mm T+E cable, running in some patches of insulation, so a nominal 34 amps current carrying capacity. Probably a little more, as the insulation is not continuous, and is patchy in the void the cable runs through.
This cable supplies 6 appliances. Oven 3.6kW, hob 6.2kW,frying plate 2.4kW, large microwave 2.6kW, Steamer 5.6kW and a warming drawer at 0.7kW. A total nominal rating of 94kW.
With the current diversity guidance in the OSG, this install complies (forgetting about the overloaded cable) with the hob at 10 amps, and the rest at 30% of their rating, giving a total of 32 amps but it just doesn't feel right. To get a little better control, and fault reduction, I had intended to put 2 extra new supplies in, to divide them up, I've since put one supply in, but the second one is getting rather difficult to install without taking apart the kitchen.
The oven (16amp) was on a plugtop, with no signs of overheating, or reports of problems from the householder. A 20 amp DP switch, which supplied the steamer, microwave and drawer did show a little heat damage, though that could well have been a loose connection.
So it goes back to the pragmatic view, how much can a small family cook at the same time, and there we have the diversity. They say there are 2 hob rings they never use, the fryer is rarely used etc. So the typical load is less than 3kW once the oven has warmed up.
Even with the Christmas day dinner cooking, I cannot see much more than 30 amps being pulled for a short period, hence no overheating of the cable, and no tripping of the circuit.
The circuit breakers are now 32 amps.
I heard a whisper that guidance on Diversity is changing, has anyone else heard what may be changing?
