To expand on winston's "Yes" answer, as you may have gathered, this is all about what is called "diversity", which is a way of taking into account the fact that, since cooking devices constantly switch their elements {separately} on/off by thermostatic control, it will very rarely be the case (except very briefly if you switch everything on from cold simultaneously) that "everything is on" simultaneously - so the average expected current drawn over any appreciable period of time is much less that the theoretical maximum.The hob is rated at 11KW. ... I dont pretend to know how the technical side of it works i am just used to seeing fat cables to ovens and hobs in the past so was concerned they were undersized at 2.5mm. Am i ok to proceed?
Yes, that's all true (I presume you mean 2.5 mm^2 for each of the ovens, separately). If one considers diversity, then I would say that 10 mm^2 is pretty serious 'overkill' but, as you say, that's not really an issue other than in terms of cost (and slightly more difficult installation, with such a 'meaty'/stiff cable!).Thanks. I think i follow this. ... They plan to install 2.5mm for the 3 ovens and 10mm for the hob. So whilst the 10mm is overkill there is also no issue with it (bar a slight increase in the material cost).
It seems that many electricians have tended to over-size cables for cooker circuits for many years - presumably either because they don't believe in diversity or (much more likely) because they are doing what they have 'learned' (from courses or other electricians).It also means the spark does not know his stuff. One wonders what else he does not know!
Personally I’d rather go with what my electrician recommended which will definitely be suitable, rather than go with what some stranger on the internet, who by the way is not an electrician and never has been, reckons might be suitable but doesn’t have to deal with the consequences if it isn’t, but it’s entirely up to you.Should i suggest something smaller 6mm?
For the 2 options TLC prices work out at £5.89p/m and £6.14p/m so a 10m run will cost £2.50 less for my suggestion, Even the additional cost of 4mm² over 2.5mm² is only £18 for 10m. No brainer to me either way.It may very well be that 3x 4mm² and 1x 6mm² is cheaper than 3x 2.5mm² and 1x 10mm²
We often hear people talking in terms of 'future proofing', and there are some situations (e.g. supplying power to an outbuilding) when it makes a lot of sense. However, in terms of cooking (and heating) appliances, I would suspect that the current (and probably 'everlasting') interest in 'energy-saving' probably means that it is very unlikely that we will see such loads getting even greater in the future..... Some will say oversized/overkill but the small additional cost is insignificant in the overall cost of the kitchen refit but in a few years when refitted again you may breath a sigh of relief. ....
No I'm advocating not using 10mm², I would go for 6mm² for the hob which is good for the 48A full load.We often hear people talking in terms of 'future proofing', and there are some situations (e.g. supplying power to an outbuilding) when it makes a lot of sense. However, in terms of cooking (and heating) appliances, I would suspect that the current (and probably 'everlasting') interest in 'energy-saving' probably means that it is very unlikely that we will see such loads getting even greater in the future.
Having said that, I agree with you that it would seem less efficient (in terms of cables etc.) to have three separate 16A oven circuits, rather than one circuit serving all three. However, the total of the OP's three ovens is only 8.9 kW, hence around 18.7A after diversity, so theoretically OK with 2.5 mm^2 cable (not necessarily Method C) on a 20A MCB/RCBO, so I'm not quite sure why you are suggesting 10 mm^2 - don't you believe in diversity?
Kind Regards, John
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