Twin built-undr ovens and 5 burner induction hob - cabling

[mdr]

Hi,
I am fitting twin Siemens built-under ovens and a Siemens 5 burner induction hob. The ovens are rated at 3,200W and the Hob at 10,800W max.
The cooker circuit was wired 2 years ago with 6mm2 T&E and a 32A MCB. There is a 45A neon switch to the side of the oven housings above the worktop.
The question I have is, can I use the existing cabling to wire in the new appliances, as the total amperage is approaching 75(!) at max power (although it will rarely, if ever be at full load during normal usage)?
If I can use the cable, should I uprate the MCB, and if so, to what size - 40A, 50A and 63A are offered?
And finally, do I need two switches at the oven end - one for the ovens and separate one for the hob, spurred off the incoming cable before it reaches the switches?
I'm worried that I will need a separate cable run in, or at least, replace the 6mm2 with 10mm2. This will require a lot of carpet lifting, etc and the house has just been decorated!
Any help and advice gratefully received.
Thanks

 

[ericmark]

You can't use any bigger than 32A MCB with 6mm cable.

Most induction hobs have boost which diverts extra power to rings being used when other rings are idle. As a result diversity can't be used with induction hob it will nearly full 47A supply likely 45A will do so it will just get away with 10mm cable and standard 45A cooker isolator. Which will leave the old 32A supply which is ample for oven and would allow upgrade to double oven in future.

However although you can replace a cooker you will not be able to install a new supply without paying the LABC their fee about £100 plus vat so it would seem prudent to use a registered electrician who will be able to advise no best method.

Do be sure to tell him its a induction hob as with old types one could have got away with smaller supply with diversity but this option is not available for induction hobs.

 

[aptsys]

Which will leave the old 32A supply which is ample for oven and would allow upgrade to double oven in future.

Sounds to me like he will be installing two ovens, hence the ~74A if everything was drawing max current. But the 32A supply should be fine for two 3.2kW ovens.

 

[Steve]

I'm worried that I will need a separate cable run in, or at least, replace the 6mm2 with 10mm2. This will require a lot of carpet lifting, etc and the house has just been decorated!

Sorry about that!

Didn't mean to be the bearer of bad news . . .

 

[ericmark]

Care and repair from local council are to re-fit my mothers kitchen and because she has only one leg are fitting an induction hob.
They have visited the house many times. Sorting out what units will fit and be of a type she can use.
I know there are no spare ways and they have already fitted a henry block for stair lift.
Also a lot of imperial cable still in the house rubber covered.
Before the rules were changed on RCD's I tried to fit one and know I had to have it supply showers, under floor heating, and garage only. And I have been trying to get my dad to permit a re-wire for years and he says he doesn't want the mess.
So I am sure they will have problems and I will sit drinking tea and see how they sort it.
Maybe when someone else other than his son and grandson tell him he needs a rewire he will listen?
The kitchen planners seem to think a supply will by magic appear. My dad is still mobile and if a MCB trips he can reset it. But what happens if Mum is on stair lift and main incoming fuse blows I don't know! She keeps cordless phone at her side not much use in power cut.
I have that feeling they will try to run cables outside the house.

If it only meant lift and relaid carpet I would be very happy.

 

[mdr]

Hi guys
Thanks for the replies. Looks like I will need to have the additional circuit wired in! I will give the guys who rewired the house a call tomorrow.

 

[ban-all-sheds]

because she has only one leg are fitting an induction hob.

I've tried to work out the connection, but I can't....

 

[Steve]

because she has only one leg are fitting an induction hob.

I've tried to work out the connection, but I can't....

In case she tries to stand on the missing leg, and topples onto the hob. My guess.

 

[securespark]

Care and repair from local council are to re-fit my mothers kitchen and because she has only one leg are fitting an induction hob.

Surely a prosthetic limb would be better?

Eric, no offence meant!

 

[ColJack]

probably the whole "leaning on a worksurface to get around" thing.. induction hobs are cold to touch after a few seconds.. so if she forgets adn leans on it it won't burn her..

 

[securespark]

Even when switched on or recently switched off?

Plus, can the hob take her weight?

Surely it would be better to fit a grabrail to the edge of the worktop?

 

[ColJack]

induction hob only switch on when they sense a large metal object on it ( some even refuse to work if you put a pan on that's way to small for it. )

as they operate by electromagnetism creating eddy currents in the base of the pan then only absorbed heat from the pan is peresent on the hob surface with a large surface area and presumably fans in the hob itself to keep the electronics cool, then the surface cools quite rapidly once the pan is removed..