New Wiring for separate Hob & Double Oven

[Stu1H]

Hi all, this is my 1st post to the forum and would really appreciate it if someone could give me some advice on the wiring for a new hob & double oven.

My current circuit is 40amp MCB at the consumer unit with 10mm2 cable to 45 amp CCU (with socket), then 10mm2 cable to terminal outlet box and our current appliance is a freestanding double oven rated 9.8 to 10.7kw.

I plan to order a new built in double oven and hob with the following max ratings - Oven 5.3kw - Hob 7.2kw and have the following questions:-

1. I plan to replace the 10mm wiring between CCU and Terminal Outlet box with 6mm2 (i'm assuming 6mm cable is sufficient as everything i've read suggests it is?) but am unsure whether to have one outlet box (connecting both oven and hob to the one outlet) or run two separate 6mm cables from CCU to two outlet boxes. What is the best option? (the hob will be directly over the oven and less than 2 metres away from the CCU).
2. Is the current MCB (40amp) ok?
3. Will I have to replace the CCU to one without a socket?
4. The installation book for the oven indicates that if the outlet box is behind the oven the top of it should be no more than 130mm above floor level - is this correct?

Any advice on the above would be great as I want to be in compliance with the regs as will want to get this and the new ring main i've put in certificated once all is done.

Thanks.

 

[ColJack]

this is a windup right?

why the hell would you want to put a smaller cable in than the one that's already in?

leave it alone..

put a dual cooker unit on where the single one is..

View media item 11376 View media item 11377
job done..

and BTW..

12.5KW = 52A... so have fun with the breaker..

ideally you need a seperate supply for the oven all the way back to the CU..

this work is notifiable under Part P of the building regs

you won't get anything certified "once it's put in" if you haven't already told the LABC that you are doing electrics in the kitchen and they do the testing..

 

[Taylortwocities]

ColJack speaks wise words Kemosabe.

BTW re your

4. The installation book for the oven indicates that if the outlet box is behind the oven the top of it should be no more than 130mm above floor level - is this correct?

Probably there is a recessed area at the bottom of the oven to provide clearance for the electric connections. And/or the back of the oven gets hot above 130mm and you dont want melty cables up there.
The rules are to follow the maufacturer's instructions. Otherwise its your fault if it goes wrong.

 

[Stu1H]

Thanks ColJack.

Can you point me in the direction of a double CCU, I can only find singles!

With the MCB assume this can be changed from 40 to 50 Amp? If so i can run both the oven and hob off the circuit providing the total wattage doesn't exceed 11.5kw.

With regards replacing with 6mm cable, i'm only referring to that between the CCU and outlet (not between consumer and CCU) as what's there at the minute isn't long enough and I have a roll of 6mm in the shed. As i understand it 6mm cable is rated to 32amp therefore can use an appliance up to 7.3kw without any issues.

 

[ColJack]

that's not the point... you must protect the cable with the breaker..
if it's a 40A breaker, you must fit cable capable of taking at least 40A..

the total wattage does exceed 11.5KW though.. I've already said it's 12.5KW..

as I've said, you'd be best off putting a seperate feed in for the oven..
that way you don't have breakers at almost twice the appliance rating protecting it..

 

[Stu1H]

Putting a separate circuit in isn't an option now as bedroom upstairs has new floorbaords / skirting / carpet etc. and kitchen ceiling just been skimmed. The Oven/Hob i was looking at (not ordered yet was 12.5kw), what i'm saying is, if i put a 50amp MCB in I can then run a hob and oven off the one circuit up to a max of 11.5kw and I'll choos appropriate appliances so 11.5kw isn't exceeded.

Would this be considered safe / in compliance with regs etc.??

Also what about the double CCU's? I cant find any on internet, they're all singles?

Cheers.

 

[ColJack]

it would depend on how and where the 10mm was run..
is it in any insulation at any point?
if it's not then it's good for 64A

http://www.alertelectrical.com/Wiri...asyfit-Dual-Appliance-Outlet-Plate-PRW217.asp

 

[ban-all-sheds]

Putting a separate circuit in isn't an option now as bedroom upstairs has new floorbaords / skirting / carpet etc. and kitchen ceiling just been skimmed.

A bit odd to have done things in that order, no?

 

[Steve]

Putting a separate circuit in isn't an option now as bedroom upstairs has new floorbaords / skirting / carpet etc. and kitchen ceiling just been skimmed.

A bit odd to have done things in that order, no?

Odd, no. Illogical but very common, yes, as you well know Ban.

 

[ban-all-sheds]

Sorry - I didn't mean "odd" as in "unusual"....

 

[Stu1H]

Cable is run straight through joist with no insulation.

Slightly illogical with the way i'm doing things, but my missus is the one who wears the trousers and our bedroom was a wreck and kitchen ceiling skimmed last week as didn't think i was going to run into any probs with the cooker circuit.

 

[holmslaw]

..

 

[ColJack]

diversity doesn't apply to individual circuits..
it applies to the overall demand of the installation, in this case the house..

you still have to install the cables and breakers to take the maximum load possible.. in this case 52A..

with diversity I can get a 10.4KW cooker on a 20A breaker with 1.5mm² T+E to feed it, but we all know that on sundays and at xmas the breaker won't hold and the cable will melt as the actual max load is 43A...

 

[holmslaw]

..

 

[ban-all-sheds]

the breaker won't hold and the cable will melt as the actual max load is 43A...

You should not be able to melt a Method C 1.5mm² with the amount of current you can get through a 20A breaker...