oven and hob.. too much for 30A?

adiwill · 6 Oct 2006

Hi all,

Fitting a new kitchen. We've currently got a 30A standard control switch and the terminal box..

I need to fit a double under oven rated at 4.2kw, and an induction hob which is stated on the website as being "Total electrical connected load (kW): 7.2 ".

now, from what i understand i need to connect the hob to the 30A supply on its own, and i can run a fused spur off the 30A suplpy to run the oven.. is this right? Or can i wire in BOTH the hob and oven into the 30A outlet terminal?

Any help appreciated..

JohnD · 6 Oct 2006

Start by taking the kW loads for each appliance and divide by (say) 230v... this will give you the amperage rating.

Now compare each of those amperages to the 30A cooker supply you already have, and the 13A that you can put through a plug and socket, or through a fused spur, both of which have max. 13A fuses in them.

Will they fit?

Steve · 6 Oct 2006

JohnD said:
Start by taking the kW loads for each appliance and divide by (say) 230v... this will give you the amperage rating.

No it wont.

7.2 / 230 = 0.0313~ amps.

However, if i take the pure wattage, the sums start to make sense!

7200 / 230 = 31.3 amps!

JohnD · 6 Oct 2006

adiwill · 6 Oct 2006

okay, so lets sum up..

I think what youre both saying is that the hob alone will command the 30A supply.. So, what can i do with the oven?

Additionally, isnt there this whole thing about diversity or something ie nothing will ever be at full pelt at the same time as everything else.. in which case i could get away with both wired in to the 30A outlet (providing the wires fitted of course )?

ta..

JohnD · 6 Oct 2006

adiwill said:
I think what youre both saying is that the hob alone will command the 30A supply.. So, what can i do with the oven?

I think you need two 30A supplies in 6mm cable. You can have a 20A MCB fitted to the one for the oven.

Although people talk about diversity, on Christmas day you will be boiling sprouts, peas, gravy and pudding on four rings; you will have the turkey in the main oven, and either potatoes and parsnips roasting or the mince pies and canapes warming in the second oven. Your MCB will trip. The moment you reset it all elements (having cooled) will draw max current and it will trip again.

adiwill · 6 Oct 2006

nah it'll be fine, we go round the inlaws for christmas

Seriously though, can i not just plumb them both in to the existing 30? WE dont use the hob much anyway..
Can i have a definite "NO, NOW STOP GOING ON ABOUT IT !" , before i resign myself to the fact i dont want the hassle and just do it anyway?
Lifes very difficult you know..

JohnD · 6 Oct 2006

No, fit a second circuit. Or buy a single oven that you can plug into a socket.

Or, BEST OF ALL, buy a Gas Hob. Quicker and more responsive, too.

You may have to get a new wife if your existing one was brought up by a mum with an electric cooker.

adiwill · 6 Oct 2006

bah.. okay.. now, onto the next question then..

Theres a 45amp supply which used to go to a stairlift for the previous owners, and its next to the consumer unit.. could i utilise that?
And thirdly, can i do it myself or do i need a sparky? I was a wireman for a few years so wont bodge it, but are unsure of theory etc.

Edit: yes, but gas hobs are fugly.. whereas my nice new induction unit melts seamlessly into the black worksurfaces

, and theyre terribly efficient dont you know..

JohnD · 6 Oct 2006

It is in a kitchen, so if you (or some electricians) do it you will have to inform your local authority and have it inspected for compliance with building regulations, for a fee. If it is done by an electrician who is a member of one of the approved self-certification schemes he will take care of this and prove the necessary Certificate. (look at the Wiki on Part P and stuff, it will help you sleep.)

If you have an used MCB way in your consumer unit then it can very likely be used for the new circuit.

adiwill · 6 Oct 2006

hmm the problem there is that its not an MCB consumer unit, its an old style fuse box (house and wiring is twenty years old)... and i think that an electrician will now not work on house electrics unless they are converted to an MCB system. Is this right?

JohnD · 6 Oct 2006

No, but anyway, 50p says you have got a Wylex Standard, and MCBs are readily available to retrofit to them.

Something like this,

Steve · 6 Oct 2006

adiwill said:
Theres a 45amp supply which used to go to a stairlift for the previous owners

adiwill · 9 Oct 2006

the 45A supply... wasn't.. in fact it was a 45A box with a 15A fuse in it..

Anyway, cheers for the replies all

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oven and hob.. too much for 30A?

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