Cable size question

[Kalico]

I do not have my OSG to hand, but can anyone tell me what the minimum cable size is to run an oven rated at 3100W (I have the manual and it only says use 2.5mm and a 20A fuse) plus a hob for which I do not have the manual but it has a 30A rating.

Also, is there a type of cooker switch that can be used to supply both devices?

At present, it has the standard cooker switch with 13A socket alongside, supplied by a 6mm cable, with the oven being supplied through a 13A plug. I suspect the 6mm will not be sufficient but it could be close, depending on diversity etc.

TIA

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[Matt Beard]

Diversity for a domestic cooker is 10A + 30% of the difference so assuming a worst case of 50A (it should only be ~44A, but the oven says

20A so let's use that) we get 10A + 0.3 * 40A = 22A

Feed this into the calculator at

(after converting to 5060W) allows 6mm to be used no problem for lengths up to about 50m.

If you still include a 13A socket you should add an extra 5A, but that's still fine for about 45m.

• Normal disclaimers apply: Check the figures yourself, dig out the OSG before attempting to cook cables etc. etc.

[Kalico]

Thanks for that Matt. Now all I need to do is find some outlet that can supply the hob, unfused (since the 6mm cable is protected by a 32A MCB at the CU) plus something in the way of a 20A fuse/MCB to supply the oven.

There must be something out there, but I cannot find it. Any ideas?

Rob

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[Matt Beard]

As the oven is supplied with a 13A plug (not uncommon) you could either:

a) Run 6mm from the cooker switch to a 13A socket behind the oven and plug it in, or

b) Run 6mm to a switched spur with 13A fuse (above work surface) then

2.5mm down to either a socket or an outlet plate

But don't run 2.5mm before a 13A fuse - otherwise it is not correctly protected.

[Dave Plowman (News)]

Hmm. It's rated at 24 amps. You could use 1mm TW&E if protected by a 13 amp fuse.

[Matt Beard]

Ok, I get your point... but I meant don't connect 2.5mm twin & earth to a 32A rated circuit without a fuse. In this case he is planning to add a fuse for the oven and I suggested 13A as this gives more options. In this case it should be >=4mm until the fuse (I'd prefer 6mm as this is what the rest of the circuit uses) then 2.5mm after. Theoretically you could use