Cooker Load in New Build

andyh · Sep 22, 2010

Installing first fix wiring in a new build and the kitchen will have a range cooker. There is no mains gas and bottled gas is not desirable. The cooker will therefore be all electric with an induction hob. The manufacturers website (Rangemaster) have a MAX load on the cooker of 17.4KW (around 75A). I have discussed this with their technical department and they have advised that as it's a domestic premises, you can apply diversity and therefore the working load is around 30A. They recommend putting the cooker on it's own dedicated 45A breaker with a 10mm2 cable. They have also stated these have been installed in a number of domestic premises without issue using the above recommendations.

Any thoughts on the above?

malcolmsanford · Sep 22, 2010

well diversity for a cooker is normally 10a + 30% of full load + another 5amp if there is a socket on the control unit

So it would be 10a + 30% of the FL as you say 75amp so would be 32,5amps + the 5amp if it as a socket.

Your 45amp could be a 40amp and stick with the !0mm^ but make sure that the 10mm^ will be enough if there are any de-rating factors.

Baal · Sep 22, 2010

I can't see a problem here, don't bother with the socket, but check that your consumer unit is up to the task (I think some old wylex units had a max of 60A total load) especially if you have an electric shower etc etc.
Contactor switching is often used in this situation but doesn't really comply with requirements for isolation.

andyh · Sep 22, 2010

It's a brand new Wylex CU rated at 100A. No intention of putting a socket on it. No electric showers either.

I was going to run the cooker off a contactor controlled via a grid switch. The contactor would have normally open contacts but when the grid switch was on, the cooker would be powered. Any problems with this arrangement?

malcolmsanford · Sep 22, 2010

Does the installation guide recommend the installation of a contactor?

andyh · Sep 22, 2010

No it doesn't. The point is I don't want an ugly cooker isolation switch and would rather control all the appliances from one grid switch. The grid switch ratings only go to 20A but utilising one of these through a contactor mounted either within the CU or next to it would allow control of the cooker via the grid switch.