Cable thickness

martin88 · 26 Oct 2020

Hi all,

I’m currently doing a new single storey extension which will become a kitchen.

We have a 6mm twin and earth cable from the board (on its own 32amp) would this provide the necessary power for the following

oven - 3.6 Kw
Induction hob 7.4 Kw
Combo oven - 3.6kw

can the oven and combi be hard wired into the same double socket?

thanks

winston1 · 26 Oct 2020

6mm cable is OK. None of those items can be used on a 13 amp socket.

whall3y · 26 Oct 2020

Presumably you have multiple 6mm² cables?

martin88 · 26 Oct 2020

Whall3y sorry I don’t understand.

whall3y · 26 Oct 2020

Total Load without diversity = 14600w / 240v = 60.8w

Even considering diversity that is about 11.5kw for each oven + 16.2kw for hob -- so just under 40kw total.

Or I guess you could calculate diversity on the combined figures which does put you under the 32A.

Personally I would have one cable for hob and another for the ovens.

securespark · 26 Oct 2020

Diversity is the first 10A then 30% of the remainder then add 5A if the cooker switch has a socket outlet.

martin88 · 26 Oct 2020

What does that mean.

I can I get away with the oven and hob on the same circuit?

I can sort the combi oven

JohnW2 · 26 Oct 2020

whall3y said:
Total Load without diversity = 14600w / 240v = 60.8w .... Even considering diversity that is about 11.5kw for each oven + 16.2kw for hob -- so just under 40kw total.

I'm not sure if that's what you intended to type, but what you've ended up typing is complete rubbish. How on earth could the "considering diversity" load be nearly three times the total load without diversity - it will obviously be LESS if you consider diversity than if you don't!

Kind Regards, John

securespark · 26 Oct 2020

What I mean is that diversity is calculated thus:

Take the first 10A of full load current.

FLC = 63.48A

First 10A = 10A

Add 30% of remainder (16.044A) = 26.04A

If your cooker switch has a socket outlet, add 5A = 31.04A.

securespark · 26 Oct 2020

With a single 6mm² cable protected by a 32A circuit breaker, you can run your cooking equipment.

whall3y · 27 Oct 2020

JohnW2 said:
I'm not sure if that's what you intended to type, but what you've ended up typing is complete rubbish. How on earth could the "considering diversity" load be nearly three times the total load without diversity - it will obviously be LESS if you consider diversity than if you don't!

Accepted

What I did men to say was ---

Total Load without diversity = 14600w / 240v = 60.8A

Even considering diversity that is about 11.5A for each oven + 16.2A for hob -- so just under 40A total.

Or I guess you could calculate diversity on the combined figures which does put you under the 32A.

Personally I would have one cable for hob and another for the ovens.

JohnW2 · 27 Oct 2020

whall3y said:
Accepted What I did men to say was ---

Fair enough!

whall3y said:
Or I guess you could calculate diversity on the combined figures which does put you under the 32A.

That is exactly what one would normally do (**) and, as both securespark and you have said, that keeps the total, after diversity, (just) below 32A.

** if one wanted to argue that one can't/shouldn't add together three cooking appliances in that way, one would presumably also have to use the same argument, and hence treat separately, for each ring on the hob, each element in the oven, etc., which would make the concept of diversity useless (i.e. since few individual bits' would be over 10A, diversity would not reduce the total at all)! In fact, it's largely because 'several things are being considered together' (with their thermostatic controls not 'in phase') that the concept of diversity is valid.

Kind Regards, John

EFLImpudence · 27 Oct 2020

whall3y said:
Or I guess you could calculate diversity on the combined figures which does put you under the 32A.

You could - because that is how it's done.

Have you ever worked out the reverse? That is, what amperage would, with diversity, be 32A.

Ignoring socket in switch:

32A - 10 = 22A
22A / 0.3 = 73.3A
77.3A + 10 = 83.3A @ 230V = 19,167W

Plus - 6mm² can carry 47A method C.

JohnW2 · 27 Oct 2020

EFLImpudence said:
You could - because that is how it's done.

Indeed so - and, as I've just explained, it's that very 'adding together' of multiple cooking loads (whether across several 'appliances' and/or within one appliance) that is actually the basis of the concept of diversity, and what makes it 'work'.

Kind Regards, John

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Cable thickness

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