Oven and Hob cabling

[flyinghaddock]

We are wiring in a new double oven (4kW) and hob (7.4kW). this equates to a maximum theoretical current of 47.5 although in practice the current drawn would be lower.
We have consulted our local recommended electrician who recommended a 50A radial and said a single 6mm cable from the consumer unit would be sufficient to supply both oven and hob. i am not convinced, but then i am not an electrician!
What is the safest and most convenient way to wire these appliances in?
- A 6mm for the hob and a 4 mm for the oven, each with their own circuit? I would rather not run 2 cables from the consumer unit but will if i have to.
- An even larger cable than the 6mm (10mm??) from the consumer unit to serve both oven and hob (as long as the oven has its won separate fused unit).

To further complicate matters, it is 20 metres from the kitchen to the consumer unit (via the loft, no alternative).

All advice gratefully received.

 

[RMS]

A 6mm cable to carry a 50A load is a no no!

A 6mm cable will carry 47amps clipped direct and even less enclosed in a wall or trunkin.

Your sugestion of a 6mm for the hob and 4mm for the cooker would be fine providing de-rating factors are acounted for and calcs for design current and volt drop are fully compliant with the regs.

I would maybe consult another electrician and make he or she fully aware of your concerns.

RMS

 

[Adam_151]

6mm² on a 50A breaker is a definite no-no, its not rated that high on any installation method.

The current drawn by them would be less than 47.5A yes, its called diversity and assumes that not everything is on together, and the rings cycle in and out on thermostats etc. You could probably get away with a 32A circuit for them both, but it just sounds a little too low for me, I think I'd probably go for a 40A circuit, in some situations 6mm² will be appropiate, but I'd use 10mm² especially taking into account the length of the run with volt drop. (though you'd have to do the calculations, but off the top of my head, it sounds like it'll be ok)

Two separate cicruits is another way out of it, but I don't think its strictly neccessary in this case

 

[securespark]

If you use 10, you can keep the 50A breaker if you wish.

Diversity is often applied. However, more and more folk design the circuit to take flc, to cope with scenarios like Christmas etc..

I would do as you suggest and fit two circuits. That way, if one goes down, you have the other. A 40A on 6mm2 for the hob, and a 20A on 4mm2 for the oven.

 

[flyinghaddock]

sorry it took so long for me to reply but THANK YOU. Have consulted another electrician after running our own cables (this involved me crawling around the loft while my "claustrophobic" husband shouted up through the hatch "think of the money we're saving"!!!) new electrican confirmed the wires are fine.
Great site. I could spend all night reading about disasters (a bit sad!)