Wiring an induction hob & electric oven

[Rogercranstoun]

The appliances will be on separate 6mm radials, so does 'diversity' apply as each will be run through separate MCBs from CU's RCB side.

Yes, I know.
I was only writing about the hob and its circuit.
The oven will definitely be alright.

The one clue I received from neff technical team was that the Oven is rated to pull 25A max.

Yes, not very helpful - 5700/230 = 24.78A
When diversity applied to oven:
10 + [( 24.78 - 10) x 0.3] = 14.43A

Does this change matters on the cooker or will 6mm through 20A MCB be OK for this appliance even with the insulating aspect?

No change.

For the hob, is 6mm 32A MCB OK

NO

or should I really change the cable to 10mm through 32A MCB? It might just be possible to pull the 6mm through the wall insulation, dragging 10mm behind it; and then connect to the 6mm in the ceiling void, repositing it on top of the mineral wool.

10 would be better but I doubt you will be able to drag it through.

Both appliances are to be operated through separate 45A cooker switches: I read somewhere that 10mm is to large to fit into these switches?

You will need the deepest back boxes.
50A cooker switch is the size of a double socket but vertical.

I have given you the figures that apply in your situation but you do not seem to have grasped it yet - no disrespect, it's not your job.

I still recommend you get an electrician - at least to have a look.

I'm slowly getting there...I think. The main issue is the insulation!!

If the 10mm won't pull through. I'm now OK with cutting into the plasterboard and removing the immediate insulation, I can replace the 6mm with 10mm for the hob. Would it then be OK to connect this 10mm to 6 mm in the ceiling void laid on top of the mineral wool back to the CU? If so, which MCB rating should be used.

Alternatively, I could cut back a wider strip of plasterboard, say 4 inches, and remove that width of insulation material. If so, am I OK to stay with 6mm all the way from the 45A cooker switch back to the CU through 32A?

Thanks for your forbearing so far!

 

[EFLImpudence]

The main issue is the insulation!!

If the 10mm won't pull through. I'm now OK with cutting into the plasterboard and removing the immediate insulation, I can replace the 6mm with 10mm for the hob. Would it then be OK to connect this 10mm to 6 mm in the ceiling void laid on top of the mineral wool back to the CU? If so, which MCB rating should be used.

This is getting to be a 'bodge'.

Either -
Remove the insulation - mind, you also said the wall was insulated - and leave the cable as it is and use 32A MCB
Or -
Replace with 10mm² for the complete run and leave the insulation as it is, and use 32A MCB.
Or -
As is with 20A MCB.

You also need one of these -

http://www.fluke.com/fluke/uken/installation-testers/fluke-1650b-series.htm?PID=56025

 

[Rogercranstoun]

The main issue is the insulation!!

If the 10mm won't pull through. I'm now OK with cutting into the plasterboard and removing the immediate insulation, I can replace the 6mm with 10mm for the hob. Would it then be OK to connect this 10mm to 6 mm in the ceiling void laid on top of the mineral wool back to the CU? If so, which MCB rating should be used.

This is getting to be a 'bodge'.

Either -
Remove the insulation - mind, you also said the wall was insulated - and leave the cable as it is and use 32A MCB
Or -
Replace with 10mm² for the complete run and leave the insulation as it is, and use 32A MCB.
Or -
As is with 20A MCB.

You also need one of these -

http://www.fluke.com/fluke/uken/installation-testers/fluke-1650b-series.htm?PID=56025

Many thanks for your patience and guidance.

At the least, I now have an idea of the alternatives the electrician is likely to propose and can plan other kitchen issues around these.