Oven and hob circuits overrated?

23 Mar 2008
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United Kingdom
I am fitting a new kitchen and am replacing my exisiting ceramic hob(5.5Kw) and oven (2.5Kw) with an new hob (6.2 Kw) and oven (2.5kw). It seemed straight forward enough but I am unsure about the existing circuits as they seem over rated. Is this a problem? My existing connections are: Hob 45A CCU on a radial circuit protected by a 40A MCB. The oven is also on its own radial circuit using a seperate 45A CCU procteced by a 40A MCB. I believe that they both use 6mm² cable. Is this ok or should i get this changed?
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I'm afraid the answer to that question is maybe, maybe not.

There are a lot of factors involved, but if you can supply the following information we should be able to give you a definitive answer:

1. Is the cable run clipped directly to a wall, in conduit, or in insulation for any of its length?
2. How long is the cable run between the CU and the Hob/Oven?
3. Are the cables run separately or grouped together?

In fact the main question here is not the 6mm cable - your new hob only needs approx 27A which 6mm will take fine. The issue is whether the cable as it is currently run should be protected with a 40A MCB or not.

The table here shows that the cable rating might be anywhere from 32 to 46 A, depending on the factors above.

Running the new appliances will be very unlikely to cause danger, as they should not overload the cable in any case, but it would still be good practise to check the figures and downrate the MCBs if necessary.

Hope that helps

Thanks Gavin

The cables run seperately loosely behind plasterboard down underneath the floorboards where i would assume that that they run along the joists but without lifting them couldn't tell you for sure. The max cable run to the consumer unit would be approx 7m as its only a 2 bed flat.
ok, in that case you should be fine with the current setup, as long as there is no insulation covering the cable at any point.

I would probably have put a 32A breaker in, but your situation seems to comply and I would certainly not call it dangerous.

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The hob should be on a 32 amp MCB.

The oven should be on a 16 amp MCB AND/OR a 13 amp FCU fitted locally to the oven (perhaps in place of the CCU)

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