6mm cable max rating and rules of diversity


A friend asked me a question I thought I ought to know the answer to, but I confess I don't so wondered if anyone else could advise?
Their cooker is a slot-in dual oven + ceramic hob and it sounds like its rated at 12Kw max and fed off a standard 6mm cooker circuit. I'd have to assume the cable is cleated to the breeze block wall and joists. So that would seem to be OK.
However, they are looking to refit kitchen and go for separate components and the question was whether they could be fed off the same 6mm circuit given this lot ends up at nearly 14kw max rating.
i.e. Inducation Hob 7.2Kw/32A, Combi-microwave 3.24Kw 15A, single oven 3.3Kw 15A
I notice the kettle is plugged into the cooker O/L too which pushes it up a bit more.
So bearing in mind a new cable will have to be run to the hob anyway as it's on a separate wall + it isn't significantly more effort/cost to get a cable back to the distribution box, if it was me I'd probably put in a separate 6mm to the hob. Or would that be being too cautious (after all, it isn't my money!).
Also, the only spare slot on their consumer unit is RCD protected. Does this cause any issues for an induction hob? I'm not familiar with these things.
TIA, Midge.
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A general rule of thumb is that a 32A supply can power upto 15kW of domestic cooking appliances.
However in this case I would be temped to run a new supply for the hob. There are no problems running an induction hob from an RCD supply.
Adam
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Thanks for your advice Adam - I was searching around a little earlier and found a rule which mentioned 100% of the first 10A, 30% of the remainder + 5A for the socket for a domestic cooker.
So assuming I understand that correctly, it would work out at 10A + 30% of 52A + 5A = 30.6A, on as you say, a circuit likely to be rated at 32A with it being in a wall cavity etc.
Couple of other things spring to mind - we're talking about a keen cook here + I think there is only one dual outlet on the wall with the hob, so an extra one on another cooker outlet wouldn't go amiss.
I think that's compelling enough reasons to suggest a separate feed is the right thing to do.
Cheers, Midge.

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Midge
If you do the maths on the microwave you have 3.24kW at 15A. That suggests a 216V supply! Something is wrong.
Adam
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I'll recheck the blurb Adam but I copied the power/current figures straight out of there. Something to do with the type of load maybe?
Midge

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