Cooker Cable (again - sorry)

In planning my new kitchen I need to decide if I am going to move the cooker location or not. I have come to the conclusion that if the existing wire is suitable I will leave the new appliances in the same location, if the cable is not suitable then I will get a new one run to a different location in the new kitchen. I have read with interest the various discussions on how relavent diversity is (which i understand, although clearly i am not an electrician or i wouldnt be asking the questions) and would welcome any comments in that area also.

The info is as follows: existing cooker 10.8kw, new cooker and hob 12.4kw combined. Cooker isolation switch does not have a built in socket so there is no additional load. Cable run from CU to isolation switch 12m, cooker circuit in CU has 40amp MCB.

Now the hard part, I can't identify what the existing cable is, there is nothing useful on it and i am also worried about it, as the previous house owner was a bit of a diy electrical botcher (i.e. the cable/MCB combination may not have been correct in the first place). I have had a look inside the cooker isolation switch at the cable and each core of the cable is made up of 7 smaller strands that look to me to be about 0.9mm in diameter. Does this imply 6mm cable? This is the bit I don't understand, in 6mm cable does that indicate the size of each cores or the two cores together? So I guess the answer to that question could also mean that it is 10mm cable currently installed?

I also found different ratings for different cable sizes. The general opinion seems to be 6mm max 37amps - 10mm max 50 amps - well at full load my cooker and hob potentially could pull 51.7 amps?? (which is why i ask the diversity question).

So in short can anyone help me identify what cable I currently have, and what cable I am likely to need?

(i suppose the other alternative is to use the existing cable for the hob and run a new one for the oven and have two isolation switches - problem there is that there are no spare spaces for an additional MCBs in my CU, 2x6mm cables into the same 40amp MCB - could that work?)

Many many thanks for any responses up front!

Alix

If you end up replacing the cable then this is notifiable work so inform your BCO before you start. Part P etc...

Regarding diversity, your new oven/hob is good for 6mm^2 cable and assuming the cable is either clipped directly to the wall or is buried in plaster and no other correction factors (running through insulation, bunched together with other cables, run in conduit etc) apply you are ok on a 40A MCB.

Sizes of T&E (including outer sheath)
6mm² 13.5mm x 7mm
10mm² 17.1mm x 10mm

If you want the capacity for close to full load then 10mm^2 cable on a 50A MCB is ok assuming same situations as above.

Davy

But if it's 4mm²...

Thanks for the prompt replies. I can confirm the entire cable run is either clipped to the wall or burried in the plaster and it is definately a 6mm cable. Looks like the applicances are staying where they are!

Secondary question though - the existing 6mm cable runs to the isolator switch that i now know is OK; is it acceptable to run two 4mm cables, one to each appliance, from the switched side of the isolator? (each appliance is pretty much half the total 12.4kw combined load).

Just thinking it would be much easier to get 2 4mm cables than 2 6mm cables into the switched side of the isolator?

Thanks again guys

You must use the same size cable.

4mm² is not rated to 40A.

of course - if i use 4mm I would have two short runs of cable that were rated below the MCB - thinking about it it was a daft question.

Thanks for all your help guys.