Oven and Hob supply

[CadmannUK]

Hi All,

I need some advice quite quickly about cable sizes etc for a new oven and hob that is being fitted into my girlfriends house.

New Twin Electric Oven. Power rating 4.4kW
New Induction Hob. Power rating 7.4kW.

The hob and the oven are being fitted away from each other, the twin oven in a tall storage unit and the hob on an adjacent worktop, but about 2m away.

The electrician has rewired the kitchen and has put in a new supply to the oven in what I think is 4 or 6 mm twin and earth. (it has a single earth core) and we have got a 45A DP switch for it.

The problem is they missed the supply for the hob which is a 7.4kW max load.

They will need to come back and address this, but I want to make sure that they do it correctly.

Some other supporting information.

Length from CU with RCB to the oven is about 13.5m max allowing for the cable rise up to hob and back down again. Cable are clipped horizontally along the wall behind the new kitchen units, but are covered when they go up past worktop level behind the plaster.

From my browsing on the net and allowing for volt drops. I think it needs to be fed by a single 10mm cable, with a current rating of 64A. Appliances can draw 51.3A on MAX load.

Is this correct?

Also, as I understand it. 10 mm T&E has a multi-cored earth ALL the time, so I should be able to tell if they say its already 10 mm installed. Like I said I don't think it is, so the whole length needs changing?

Also, they want to fit the hob isolater in one of the units, screwed to the back panel is that OK. Can you fit 10mm into switches OK.

The other thing I need to know is that the hob manufactirer (AEG) say to use this type of cable. H05BB-F Tmax 90degC. What is that as I've not heard of it and can't see any cables like that in the DIY warehouses.

I know they might say that it should be OK with the cable they have fitted, but at Christmas and East you will probably have both ovens and hob going full tilt, so will be using the MAX load of 11.8kW.

I'm not being stupid am I. I see it as its better to be safe than sorry.

Thanks
CAD

 

[EFLImpudence]

If it is protected by a 32A mcb then 4mm² cable is sufficient.

This is less than the total amperage you have calculated because of what is called 'diversity' because ovens/hobs/cookers do not have all the elements drawing maximum current all the time.

Normally cooker circuits are 32A mcb and 6mm² cable.
This is good for up to 15kW.

 

[PrenticeBoyofDerry]

It is possible to connect both appliances to to the same outlet plate.
Although your maximum output values are 4.4kW and 7.4 kW totalling 11.8kW.
It is very unlikely this demand would ever be possible, even if both units were on at full tilt at the same time.
We are allowed to use a diversity factor for output which would allow 15kW of power on cooking appliances to need no more than 32A protective device, so it is then feasible to have the circuit in 4.00mm T&E although always recommend 6.00mm T&E. (voltage drop and method installation permitting)

10mm T&E cable does not have multi-core earths, it will have stranded cables as will 4.00 and 6.00mm T&E.

The H05BB-F is heat resistant flex which would connect to the appliance via the outlet plate.