Oven and hob cable size and isolating switches

[johnmadbag]

Thanks for adding me to the forum.

I have done quite a bit of electrical work around the house adding sockets, and at our current house I put in some new ring mains and lighting circuits, all subject to third party certification and with the new consumer unit installed by a qualified electrician, which all passed with flying colours.

I have never had to think about oven and hob cables because the current house had a surplus 10mm cable sitting above the new kitchen, which I rerouted, and the third party cert company were quite happy.

I am about to start something similar with the new house, and I need to put in a new cable (or cables) for the cooking appliances. The kitchen is U shaped. There will be an oven, and a microwave/oven together in a tall unit against the wall. They are both rated at 3.6KW, 7.2KW in total. Cable run will be about 10m from CU to back of cabinet.

The ex display kitchen to be fitted has a large gas hob on the other side of the "U" in an island. If I don't like it I might want to replace a 5 ring induction hob of as yet unknown rating, so I plan to pre-wire round to the island. It's probably 8 metres cable run max round the island from the oven.

So what cable should I lay to the ovens, and what to the island hob?

Or should I take up two slots on the CU and lay two 6mm cables, one to each location? I have about 20m of leftover 4mm (some radial work I did), could I use that for one circuit if I went with two cables?

Finally, there is a mass of opinion online about oven and hob isolators. I have always preferred them on wall close to hob and oven, but in this case there is no wall near where the hob might go, and the oven housing is in the middle of a run of 5 full height units, so no wall there either. Is it OK to put them in a cupboard close by?

Thanks in advance

John

 

[Jamie']

I would personally run two 4mm radials on 20A double pole switch for the oven and oven/microwave. I would run a 10mm for the possible induction hob on a 45a isolator. Putting either in a cupboard near the grid switching for the appliances.

 

[Spoon]

Welcome to the forum mate.
I'd have a word with the electrician who is going to put their name on the cert. They should give you all the advice you need.

 

[A032701]

put the hob on a 10mm radial from a 40amp mcb and then put a 45amp cooker switch to isolate the hob if you need to.
the ovens and microwave you can use on 20 amp mcb rads using 4mm cable and then some 20amp switches to isolate the ovens if needed

 

[45140]

Finally, there is a mass of opinion online about oven and hob isolators. I have always preferred them on wall close to hob and oven, but in this case there is no wall near where the hob might go, and the oven housing is in the middle of a run of 5 full height units, so no wall there either. Is it OK to put them in a cupboard close by?

Therein lies the problem, speculation by the unknowing !

The answer to your questions lies in BS7671, and the Building Regulations which you should be using as your guidance rather than unknowing keyboard "experts" speculating an opinion.

The Building Regulations recommend that the cooker / hob switch/es are placed within 2m of the equipment.

Switches must be visible and must not be located in cupboards unless they are easily accessible. Not always the case when a cupboard is used;

By the way the Building Regulations also specify that an unqualified installer must notify Building Control of notifiable work before the work starts.