Cooker and Hob Power ratings

[tucker2969]

Hi,

I am looking to fit a new kitchen, and currently looking a a Bosch induction hob and seperate built in single oven. i have had a couple of quotes to move electrics, but split 50/50 as to whether i need a new consumer box. 2 have said i do and 2 have said i dont.

the current wiring is from about 1990, and is in OK condition. i currently have a 32amp cooker connection, which 2 of the sparkies have said they can run the cooker and the hob off, but will move it to the new location. the other 2 have said i cant and i need a new consumer box as they dont make the trip switches any more.

the hob is 4.6Kw and the Oven is 3.5KW. The two electricians who have said i can run it off a two point cooker circuit have said these will be ok on a 30amp circuit. is this right?

the reason i question, is because two other electricians have said i should change the consumer unit, but im not sure if they just want money for old rope - the 2nd reason is that on one of the cooker reviews, the comment from someone says that as the cooker is 3.5Kw that it can pull up to 15amps, which is half of the circuit.

so....my question is, can i put a hob at 4.6kw and an oven at 3.5kw on a 30amp circuit??

Thanks
Alan

 

[ban-all-sheds]

Yes you can - see Table 6.2.

8.1kW comes to a diversified load of 17.6A, or 22.6A if the cooker control unit has a socket.

Ask the 2 who've said "no" what their reasons are. It is quite possible that the manufacturers instructions for the oven specify that it should be on a 16A circuit, in which case they are right, it'll be one circuit for the hob and one for the oven. This is a common "problem" with makes like Bosch, Siemens etc - in mainland Europe 16A socket circuits, and sockets which handle 16A are the norm, so they make ovens which can just be plugged in. Over here our sockets max out at 13A, so the ovens can't be plugged in, and if the maker says use a 16A circuit you can't use a 32A cooker one.

Also do you have RCD protection? That's now effectively mandated by the Wiring Regulations for concealed cables.

But you wouldn't need to replace your CU, just have an additional one for the oven circuit. If you think that at some time you'll be replacing your existing CU, e.g. to get RCD protection or better RCD granularity, or RCBOs, or extra circuits, then if you've got the space have a full-sized CU installed, the extra cost of a bigger mostly empty plastic box will be trivial.

 

[ericmark]

Before getting an induction hob I read the spec and it refers to a boost and because it can power share I considered that the diversity factors normally used did not work. However when I got one myself (Belling stand alone) I noted the manufacture still recommended a 32A supply even when with the oven able to draw around 6kW (Three elements top, bottom and back fan) and grill another 3kW (double element) and two hobs being 3kW and 3.7kW on boost can be run together in theory one could hit the 18kW mark. I don't know if Belling have included some method to stop the overload but it has never taken out the B32 amp MCB so clearly they were right in saying 32A.

After using the induction hob I quickly realised except with water alone the boost was really too much. It boils that much quicker than even gas to use the boost in most cases means something will stick on the pan. It is easy with knobs to turn the heat down you don't any longer have to lift a pan to stop it boiling (unless you have silly touch controls) so unlike the old hot plates where the heat is on even when not required you only use what is needed. So the room is cooler and you use less power on average. So although it can give more power in real terms it uses a lot less.

However I only realised this after using one so I can understand any electrician being a little apprehensive when connecting up a hob with so much power being at the turn of a knob.

So the only problem is the oven which is over 3kW so can't go on a FCU but is under the 16A used in Europe as may stipulate a 16A supply. A garage or bathroom mini consumer unit could be used to reduce the supply to the oven but this would depend on design of house.

I took easy way out. I bought British and yes it's designed for a British kitchen with British power supply.

 

[tucker2969]

Hi,

thanks for the advice. the tech specs are here:

Hob:

http://www.bosch-home.co.uk/our-products/cooking/hobs/hobs-range/PIA611T16E.html

Oven:

http://www.bosch-home.co.uk/our-products/cooking/ovens/ovens-range/HBA43B250B.html

both are bosch which is typical!!

 

[ericmark]

OK for oven manufactures instructions must have a local isolator or must be plugged in with a plug that remains accessible.
They say it needs a 16A supply but nothing as to maximum supply.
The hob it seems is programmable although reading instructions would not want to be the guy to do it and although it says 4.6kW which equals 20A it also says the programs can be set for 10A, 13A, or 16A supply.
So with the information available seems both will run without problem from a 32A supply.
It seems you can set max power for each heat area down to 1kW, 1.5kW, or 2kW however it would seem to be defeating the whole idea of having an induction hob if you then limit the power it can run on.
I would not say either set of electricians were wrong. The installation instructions are some what lacking leaving it to the electrician or as the manual puts it "licensed expert" to decide.
I hate phrases like licensed or authorized as to mean anything they need to state by whom. So I would say it must mean a "Bosch licensed expert" I know according to BS7671 we have to follow manufactures instructions but I don't read German and the English version is somewhat lacking.