Hob and double oven

Hi folks just a quick question..

I have a new kitchen coming in and the hob total output is 6.7 kw.

The double oven total output is 4.2 kw.

Will the existing 6mm cable on a 32amp Mcb from the fuse board be enough. The board is very close to the cooker switch it’s only a 10metre run.

It wouldn’t be handy to get another 6mm cable to feed the oven seperately but if it needs done.

Combining them both is probably ok but if you can get a 2nd circuit in easily it wouldn’t harm

proper testing etc needs to be completed

10.9kw in total is 47A @230v you will need a second circuit.

awarner said:

10.9kw in total is 47A @230v you will need a second circuit.

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er no.

apply diversity CORRECTLY to such appliances before misleading people please

Diversity rule is (unless its changed): first 10a plus 30% of remainder.
so, 10a then 30% of 37 is 11 add the 10
total load 21a

Diversity rule makes the assumption that you will never use all the rings and both ovens/ grill at once. so a 32A circuit using 6mm cable will be more than adequate for connecting oven and hob.

Addis1988 said:

Hi folks just a quick question..

I have a new kitchen coming in and the hob total output is 6.7 kw.

The double oven total output is 4.2 kw.

Will the existing 6mm cable on a 32amp Mcb from the fuse board be enough. The board is very close to the cooker switch it’s only a 10metre run.

It wouldn’t be handy to get another 6mm cable to feed the oven separately but if it needs done.

Click to expand...

More than enough. In fact the cable could be 4mm.

Thanks for your replies.

Just another question on the same topic..

The new double oven is being positioned a few meters (4m in total) away from the hob not directly below it. Is it an option for me to get a dual connection outlet plate and take both supplies from this or what other options would I have?

cant see why not. seems best option.

Diversity is fine, but I also use the Christmas Day rule !

mort2376 said:

Diversity is fine, but I also use the Christmas Day rule !

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I think I would be with you there, especially if it's only a case of a few extra metres of cable whilst work is going on anyway. Separate circuits would also give the advantage of redundancy in case of a fault. i.e. you wouldn't lose everything at the same time.

Addis1988 said:

Hi folks just a quick question..

I have a new kitchen coming in and the hob total output is 6.7 kw.

The double oven total output is 4.2 kw.

Will the existing 6mm cable on a 32amp Mcb from the fuse board be enough. The board is very close to the cooker switch it’s only a 10metre run.

It wouldn’t be handy to get another 6mm cable to feed the oven seperately but if it needs done.

Click to expand...

First just to confirm some of the math's stuff... Power(Watts)=Volts x Current(Amps)
so Current(Amps) = Power(Watts) / Voltage..

or in your case.. where 6.7kw is 6700watts and 4.2kw is 4200watts... Grand total of 10.9kw (10900watts)
So 10900watts / voltage = current..

BUT.. you would need to double check what voltage the manufactures spec is referencing to...?

As some manufactures, (especially with electric showers), quote power ratings ref 240v..
Not the 230v nominal values used by BS7671` wiring regs..

e.g.
10900w / 230v = 47.39amps
or
10900w / 240v = 45.41amps

This is ASSUMING EVERYTHING could be turned on simultaneously!
Which is where the Diversity calculation mentioned earlier comes in..

BUT diversity is NOT a fixed set of 'one-size-fits-all' rules..
It is guidance to be used by a competent person familiar with the specific installation requirements and expected usage..
And it is possible that actual level of diversity may be higher, lower or not applicable at all!

Also a thing called the installation method will affect how much current a specific cable can safely carry, without potential heat damage..
Dependant upon installation method a 6.0mm CSA T&E cable can be good for 45amps +/- a few percent tollerance..

And I know of several 10.5kwatt showers running happily off a 6.0mm cable via a 45a MCB..
Which would suggest your Oven/Hob arrangement would not be a problem on a 6.0mm cable, but may need a larger MCB?

HOWEVER!............

If you are investing your hard earned time and money into a new kitchen...
I think its generally best to also invest a bit into any possible electrical upgrades improvement's at the same time..
(while an extra supply may not be essential, it could be very beneficial.)

If its just an appliance that's been replaced then you often have to make do with what supply is already in place and work around that!

So to summarise my evaluation..

The existing supply may be OK..
But adding a second supply would be my personal preference unless costa are really astronomically prohibitive!

It could be worthwhile getting an electrician round to asses exactly what's feasible and the costs..

hope that helps?

BorisJ said:

More than enough. In fact the cable could be 4mm.

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Or maybe not.....
Installation method possible implications???

To the OP, stop faffing around (technical term) if you can get another circuit in without too much trouble go ahead and do it, if you can't without ripping the kitchen to bits then use the existing circuit, but upgrade the MCB.

Mike.J said:

To the OP, stop faffing around (technical term) if you can get another circuit in without too much trouble go ahead and do it, if you can't without ripping the kitchen to bits then use the existing circuit, but upgrade the MCB.

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I would suggest that advice is inappropriate as you do not know the installation method for the installed cable.

I do know the installed method - the fuse board is in the kitchen and the 6mm twin and earth has been pulled through wooden joists and then down into a 20mm conduit into a 35mm steel box. The cable run from the board is no more than 8metres long. Yeah it’s hassle getting a new circuit in to be honest.

Addis1988 said:

I do know the installed method - the fuse board is in the kitchen and the 6mm twin and earth has been pulled through wooden joists and then down into a 20mm conduit into a 35mm steel box. The cable run from the board is no more than 8metres long. Yeah it’s hassle getting a new circuit in to be honest.

Click to expand...

Running in a 20mm conduit will de-rate the cables capacity.. (reducing the max current capacity.)

Is there an isolator switch somewhere in this arrangement..? As a 47mm is a far better selection for this purpose than a 35mm back box..

Yes there is a 45A doubled pole Switch and then it goes down to a cooker outlet plate….

SPECIAL LOCATION said:

Running in a 20mm conduit will de-rate the cables capacity.. (reducing the max current capacity.)

Click to expand...

Maybe, but as the cable is over rated anyway (4mm will do) I doubt it is a problem. Remember the appliances will never draw (even on Christmas day) their full rated current as the various elements cycle on and off on their thermostats.