Cable size for two ovens and a hob from extension CU with 6mm supply

[SJRSJR]

Hello

Later this year I plan to get a new kitchen. I currently have a gas oven and hob but was wondering about the viability of electric.

The kitchen is in an extension that has a bedroom/en suite above. There’s s a 6mm supply cable (max 20m) from the main consumer unit to another CU in the bedroom, to which the extension sockets, lighting and bathroom extractor fan are connected.

Ideally I’d like two electric ovens with the option for an induction hob. Could all that run off a 6mm cable from the bedroom CU?

Thanks.

 

[ETAF]

just as an aside, you may not like Electric hob , i know we didint like it when we moved in and had an electric hob, which i think had part induction - anyway we changed back to gas when i did my kitchen refit , ovens are great electric - just the hob we both didnt get on with
as i say just an aside

 

[EFLImpudence]

Ideally I’d like two electric ovens with the option for an induction hob. Could all that run off a 6mm cable from the bedroom CU?

Not unless you disconnect everything else.

 

[SJRSJR]

Thanks - could you elaborate? For example, does the 6mm supply in to the CU restrict everything out? Would that have to increase to 10mm before anything else?

 

[EFLImpudence]

does the 6mm supply in to the CU restrict everything out?

It might be possible to 'fiddle' the figures to make one 6mm² cable supply everything but it's not really big enough.

Would that have to increase to 10mm before anything else?

Possibly - or you need another 6mm² cable for the cooking appliances (possibly 4mm² depending on the cable run but just use 6mm²).

 

[SJRSJR]

Thanks. So it would be okay to run 2 x 6mm cables without increasing the feed in from 6 to 10?

 

[EFLImpudence]

So it would be okay to run 2 x 6mm cables without increasing the feed in from 6 to 10?

You need another 6mm² from the main CU to the cooking appliances.

 

[SJRSJR]

Oh dear, that's going to be a problem. Gas it is...

 

[EFLImpudence]

Oh dear, that's going to be a problem.

Surely no different than changing it to 10mm² would be.

 

[SJRSJR]

Running cable from the extension CU to the kitchen below would be relatively straightforward. Upgrading the current 6mm cable (or adding a second one) from where the main CU is to the extension CU would be tricky. (It’s not actually in the CU, it runs from a main switch below)

 

[JohnW2]

Not unless you disconnect everything else.

Is that necessarily the case?

It obviously depends a bit on what is meant by 'two ovens', but it may not be any worse than a (common) 'double oven' - maybe 5 kW total (about 13.6 A after diversity), and we know that inductions hobs can be limited to 13A (sometimes less), hence about 10.9 A after diversity, so a total after diversity of around 24.5 A. If all the 6mm cable is installed by Method C, that would be a CCC of 47A, hence leaving something like 22.5 A for 'everything else' supplied by the bedroom CU.

Certainly not ideal, but I'm not convinced it would necessarily be 'impossible', would it

 

[EFLImpudence]

Is that necessarily the case?

It obviously depends a bit on what is meant by 'two ovens',

and a hob.



I knew someone would say it.

That's why I said:

It might be possible to 'fiddle' the figures to make one 6mm² cable supply everything but it's not really big enough.

 

[SUNRAY]

Is that necessarily the case?

It obviously depends a bit on what is meant by 'two ovens', but it may not be any worse than a (common) 'double oven' - maybe 5 kW total (about 13.6 A after diversity), and we know that inductions hobs can be limited to 13A (sometimes less), hence about 10.9 A after diversity, so a total after diversity of around 24.5 A. If all the 6mm cable is installed by Method C, that would be a CCC of 47A, hence leaving something like 22.5 A for 'everything else' supplied by the bedroom CU.

Certainly not ideal, but I'm not convinced it would necessarily be 'impossible', would it

Whenever I've offered my doubts before there has been the chorus of a hob and an oven is no different to a cooker and the total power has diversity applied. On that basis 5KW = 22A + 13 = 35A, diversity comes out at ~18A not your 24.5A

I'm definitely not saying I'd be happy with a 2.5mm² and 20A OCPD though.
FWIW Dinner is cooking ATT on 3 rings and oven. For the last few minutes a clamp has shown 23 to 31A 11.5KW comes out at 22A I believe.

 

[EFLImpudence]

The kitchen is in an extension that has a bedroom/en suite above. There’s s a 6mm supply cable (max 20m) from the main consumer unit to another CU in the bedroom, to which the extension sockets, lighting and bathroom extractor fan are connected.

Running cable from the extension CU to the kitchen below would be relatively straightforward. Upgrading the current 6mm cable (or adding a second one) from where the main CU is to the extension CU would be tricky. (It’s not actually in the CU, it runs from a main switch below)

I'm confused about the origin of the supply cable.

 

[JohnW2]

I knew someone would say it. ... That's why I said:

You did, but I would not describe anything I wrote as being 'fiddling' - other than possibly in the eyes of someone (I don't think including yourself) who does not believe in the concept of diversity.