Recommended power provision for hob and oven

[MJNewton]

The design of our new kitchen for our open-plan extension is slowly maturing and, having decided what induction hob and double built-under oven we want, I would be grateful for opinions on what power supply(/ies) to run to them. The specs are:

 

Hob: AEG IKB64401FB, Total Loading 7350W (/230V = 32A)

Oven: AEG DUB331110M, Total Loading 5300W (/230V = 23A)

 

The route from the CU to the hob+oven is pretty straightforward: Up 1m inside an uninsulated stud wall, across 5m inside an uninsulated ceiling and down 1.5m behind uninsulated plasterboard.

 

Taking the IET OSG guidance on diversity for cooking appliances, the total supply requirements would be:

 

First 10A + 30% of remainder = 10 + ( ((32+23)-10) x 0.3) = 10 + 13.5 = 23.5A

 

If my understanding and calculations are correct a single 6mm2 going to a single 45A DP switch (a rare white one!) and dual appliance outlet plate should suffice. This would be adequately protected by a 32A MCB.

 

However, for future proofing (and better/safer? operation) should I put two 6mm2 cables in instead, each with there own 32A MCB? Or perhaps a single 10mm2 with a 40A MCB? Running cable is easy at the moment as the ceiling is down and I have open access to the rear of the CU (which, whilst a bit tight for wiring, does have some spare ways).

 

Note that this open-plan extension is being done under building control and so, with the hob+oven being a new circuit and therefore notifiable, I plan to get an electrician in to do the work (and, more importantly, give me the necessary certificate for sign-off) however I wanted to give some thought myself to what we should do in advance of asking them (whoever that might be).

 

 

[ProDave]

I would have done the sum as 10 + 22*0.3   + 10 + 13 * 0.3

 

= 30.5

 

i.e done the 10 + 30% of the remainder for the oven and the hob seperately then add them together.

 

Result to practical purposes is the same.

 

I would still be inclined to fit 10mm because you never know what you might want in the future.

[MJNewton]

18 minutes ago, ProDave said:

i.e done the 10 + 30% of the remainder for the oven and the hob seperately then add them together.

 

I did wonder about that, but was picturing things as if I had a combined hob and oven (a 'cooker'), but I suppose that's not what I have so probably shouldn't!

 

I also wondered that, if leaving diversity aside, if the hob and oven are both turned on running flat out (all rings, both cavities - Christmas dinner sort of thing) until the stats open they'd be drawing 55A which is surely pushing a 6mm2 cable towards sweating a bit.

Edited November 2, 2019 by MJNewton

[MJNewton]

On 02/11/2019 at 22:25, ProDave said:

I would still be inclined to fit 10mm because you never know what you might want in the future.

 

Thinking about this further, I am assuming I would have to run a 10mm tail to the hob (and the oven) given that the MCB would be rated for a 10mm cable and nothing smaller? I haven't wired up a hob or oven for a long time, but would they take a 10mm cable?

[ProDave]

Fit 10mm from CU to isolator to Cooker Connection Unit.

 

You can then use a 6mm tail from there to hob and oven with 32A mcb.  the purpose of the thicker cable is "in case"

[MJNewton]

Ah, yes, that makes sense. Tails for a future appliance would then of course be something to consider then. I was assuming a larger cable would've also meant a larger MCB from the outset.

[ProDave]

Not at all.  I have a 10mm cable to our island, currently fed from a 16A MCB just feeding a 3 gang pop up socket.  The large cable is there in case we change the gas hob for an induction hob.