Wiring a Hob and Oven

Ya, C32 indicates its mcb rated at 32 amps. The wire twin and earth is 6mm. As said there should be two feeds from the fuse board - one for the hob and one for the cooker. The C32 mcb feed is for Hob with 6mm cable.

iba · 21-10-2023 10:26am

https://www.boards.ie/discussion/comment/121265106#Comment_121265106

Thanks for your input.

Cheers

Risteard81 · 21-10-2023 12:18pm

https://www.boards.ie/discussion/comment/121264703#Comment_121264703

I wouldn't agree with them ideally being separate circuits. A combined cooker circuit is perfectly normal and satisfactory.

Risteard81 · 21-10-2023 12:20pm

https://www.boards.ie/discussion/comment/121265106#Comment_121265106

One 32A cooker circuit is perfectly satisfactory for cooking loads nominally up to 15kW due to diversity. It's really not an issue at all. There is likely to be absolutely no benefit whatsoever to having them as two separate circuits.

kirk. · 21-10-2023 1:26pm

"The boost function allows you to cook elaborate dishes simultaneously, give you up to 50% more power for 5 minutes, whether you're boiling liquids or searing meats.

Total Power : 7200W Left Front Zone : 2000/2400W (boost) Left Rear Zone : 1600 / 2000W (boost)

Right Front Zone : 1600/2000W (boost) Right Rear Zone : 2000/2400W (boost)"

I assume the boost is full-on (no thermostatic control) for the 5 minutes

How many will boost simultaneously ?

And where's that 50% figure coming from ?

iba · 21-10-2023 3:02pm

https://www.boards.ie/discussion/comment/121266610#Comment_121266610

Thanks for your input.

So you are suggesting that I could just join the oven and the hob in the Dual connection plate?

iba · 21-10-2023 3:09pm

https://www.boards.ie/discussion/comment/121266852#Comment_121266852

Thanks for your input.

Difficult questions :

I assume the boost is full-on (no thermostatic control) for the 5 minutes = I dont know, will have to try and find out

How many will boost simultaneously? = probably only one for the foreseeable future, if even used at all.

And where's that 50% figure coming from ? = I see what you mean. I dont know. Ill try and find out.

Cheers

leinster93 · 21-10-2023 3:47pm

https://www.boards.ie/discussion/comment/121266610#Comment_121266610

Just curious - Let's say at Xmas everything is turned on on hob and everything on the cooker. total draw of power is 7200W + 3400. 10400 watts

÷ 220 volts gives 47 amps

With a single feed of 6mm cable and an mcb of 32 amps it will trip at 47 amps.

If there were two separate feeds, one for cooker and one for Hob then it would be fine.

Would Joining the hob and cooker onto single feed with 6mm cable and C32 mcb be wrong - ???

21-10-2023 4:05pm

6mm2 is inadequate for 47 amps. You'd need a separate circuit for the hob. If the fuse board is near by, it shouldn't be a big deal to do.

I'd also point out if you're in Ireland, it's basically illegal for you to install another circuit on the board yourself. You need an electrical contractor.

leinster93 · 21-10-2023 4:49pm

https://www.boards.ie/discussion/comment/121267539#Comment_121267539

Yes any tampering with fuse board unless registered electrical contactor is illegal. But on an educational note - 10mm cable with the correct rated mcb.

Risteard81 · 21-10-2023 5:07pm

https://www.boards.ie/discussion/comment/121267332#Comment_121267332

I haven't seen your installation, but assuming that it is a normal oven and hob setup with a cooker circuit then yes. (The isolator must be local to both appliances, but I assume that the hob is directly above the oven.)

Risteard81 · 21-10-2023 5:09pm

https://www.boards.ie/discussion/comment/121267481#Comment_121267481

Even with everything switched on that simply isn't true though. Quoted "total connected load" often cannot even be simultaneously energised. And the bits that can will thermostatically cycle. Try running it with a clamp-on ammeter sometime. I guarantee you will not be within an asses' roar of the 47A that you are imagining.

Risteard81 · 21-10-2023 5:10pm

https://www.boards.ie/discussion/comment/121267539#Comment_121267539

It's not 47A though. Diversity is key here, particularly with something like cooking loads.

leinster93 · 21-10-2023 5:13pm

https://www.boards.ie/discussion/comment/121267734#Comment_121267734

Yea, I think rating and absolute values are two different things but "ratings" put in place for protective measures where worst case scenario...

Risteard81 · 21-10-2023 5:15pm

https://www.boards.ie/discussion/comment/121267753#Comment_121267753

On cooking loads with "tcl" (total connected load) it isn't even worst case scenario. It's simply an attempt to make the appliance look more powerful. For example, it's not possible to simultaneously operate the oven and grill - but these ratings will have been added together.

kirk. · 21-10-2023 5:30pm

https://www.boards.ie/discussion/comment/121267734#Comment_121267734

Total connected load is 7200w for the 4 hob zones

Boost load is 400w extra each

I'm not clear how many boost you can operate simultaneously

Risteard81 · 21-10-2023 7:18pm

https://www.boards.ie/discussion/comment/121267799#Comment_121267799

With my induction hob as an example, you can boost one zone on each side (i.e. 2). But this is for a short duration as once the pan is boiling then the hob will automatically disengage boost and return to the original setting. Obviously, as mentioned previously, the zones will cycle on and off and will not simultaneously draw power for any real duration. Diversity with cooking appliances is long proven. Christmas Day will give no issues.

kirk. · 22-10-2023 10:31am

Never heard of issues with hob and single oven on 32A

I ran a 2.5 and 6 to a 47mm dual box to follow manufacturers instructors on the single ovens

I thought there was an issue with diversity and induction hobs but maybe not

iba · 22-10-2023 3:28pm

Thanks everyone for all your inputs

My understanding from reading everything, and maybe I'm reading wrong, is that the job can be done joining both oven and hob onto the 6mm cable to the 32 Fuse

But it would be preferable to have them on two circuits:

1) Put the oven on the current 6mm, cooker switch and 32 fuse

2) Put the hob on new 10mm cable, new isolator switch and a 45amp fuse

Taking the xmas dinner example above. I doubt very very much that the full load would ever be reached in the foreseeable future

With regards the fusebox. Yes I understand only qualified sparkys can alter it. I could though try and get the cable there and then the sparky just has to connect up.

But that's the problem. Getting a cable there. If I could do it, I would do it no problem. I'm just not seeing how I can get a cable there. But if there is a will there is a way.

Added some pics to answer some other questions:

1) cooker switch is on the opposite wall by the washing machine

2) oven is not under the hob, but by its side

3) the 3rd pic is the location of the fusebox. Its across the hall from the back of the hob and oven. And I cant get a cable there hidden behind the skirting boards because the front door is in the way. The only way Im seeing of getting a cable there atm, is up from the hob, under the floorboards and then down to the fusebox.

Cheers

IMG_20231022_150459.jpg

IMG_20231022_150434.jpg

IMG_20231022_150318.jpg

kirk. · 22-10-2023 3:40pm

The existing 6sq supply should be adequate for both connected together there as risteard was saying

If you ignore boost , hob total load is 7200w

Assume 2kw max total load for the single oven

That's 9.2 kw which is 40amp before diversity

So should be no problem with loading anyhow in reality

kirk. · 22-10-2023 3:56pm

Manufacturers instructions on fusing the oven could be a concern if it caused a warranty issue

In reality this is probably a minor issue

The internal wiring and appliance cord can't overload and in a short circuit a trip should occur without damaging wiring

22-10-2023 7:05pm

Just beware though that induction hobs and traditional hobs are very different beasts in terms of how they use electricity.

They're very efficient, but they pull massive amounts of energy when they're in rapid heat mode / boost.

They have interlocks in the control systems to prevent you exceeding the wattage on the rating plate. Some of them also configure themselves differently if they're connected to 230V vs 400V i.e. they'll split the zones across multiple phases and allow simultaneous use if that's available.

The boost however can be on for up to 3 or 4 mins in some cases and it is enough to trip breakers or cause overloading - I've seen it first hand.

We'd a wide Miele hob which pulls a full 11kW if you put it into certain configurations and those last for anything up to about 4 mins or so until it brings pots to the boil and it will absolutely overload things. Diversity applies to some degree, but just don't calculate it as if they are traditional radiant hobs.

7.6kW+ isn't unusual.

The other thing to bear in mind is they're not a resistive load. They don't behave like an AC electric motor either, as they're sitting behind system of rectifiers and inverters and other electronics that produce an output that's usually in the 40-50kHz range but anywhere from about 20-100kHz. Some also use variable frequency. They don't surge but they can drop the full load onto the circuit very suddenly compared to a resistance heater.

kirk. · 22-10-2023 7:35pm

You're probably right , you have to add-on for the boost

How would you calculate it though

iba · 23-10-2023 7:38pm

https://www.boards.ie/discussion/comment/121271757#Comment_121271757

Thanks very much for your detailed input

leinster93 · 23-10-2023 10:40pm

https://www.boards.ie/discussion/comment/121270983#Comment_121270983

Had a similar situation but difference was the kitchen hadn't been installed so made things a little easier. Floor board opened upstairs above kitchen to facilitate running cable from switches to fuse board for sparky to connect up.

iba · 24-10-2023 11:24pm

https://www.boards.ie/discussion/comment/121276518#Comment_121276518

I havent finished installing that side of the kitchen. Its not all screwed together and fitted in place permanetly. I can move it and get behind it.

I had an electric shower put in a few years ago and the guys that did it, did cut open the floorboards on the landing to get the cable to the fusebox

These cut boards are now screwed down, so Im going to open them up and see if its possible to get a cable that way

If that fails. Will also see if I can get a cable to go over the front door - maybe there is space above the plinth.

How much did the sparky charge to connect the fuse?

Wiring a Hob and Oven

Comments