Fair enough. Looking back, I see that's the case, I was (unnecessarily!) confused by ...No I'm advocating not using 10mm², I would go for 6mm² for the hob which is good for the 48A full load.
It may very well be that 3x 4mm² and 1x 6mm² is cheaper than 3x 2.5mm² and 1x 10mm²
Who knows, but, as I implied, I think there will be an "ever increasing" desire to reduce, not increase, the total energy consumption of all appliances in kitchens (and elsewhere)I agree with your comment about loads not increasing however the trend for ever increasing appliances in the kitchen seems to continue which is where I'd suggest increasing the size of the cables for the ovens.
... which seems to be saying that you do not believe in diversity (at least, per the current standard calculations), isn't it? It sounds as if you are probably being influenced by the fact that, 'as it so happens', we are talking about three physically separate 'appliances', and I suspect that you might think a little differently if the OP's total ('maximum') of 8.9 kW was all in 'one appliance' (quite credible for a hob, and certainly a 'cooker')?Don't I believe in diversity? Oooo... tricky... yes I do but... No way on earth would I ever put those three appliances on a single 20A circuit.
I'm not sure that is necessarily the case. Diversity calculations don't really have that much impact until one gets up to quite high total ('maximum') loads and, as above, whether the total ('maximum') load relates to 'one box' or 'several boxes' is irrelevant.My view is diversity has outlived its intended design purpose .... I'm not convinced diversity was originally intended to apply to multiple appliances in the way that some happily do without due consideration to their usage.
That ("fir 1/2 hour or so") actually rather surprises me but, even if I experienced that, it would not cause me any 'discomfort'. Don't forget that a cable suitable for protection by a 32A OPD is deemed to be able to carry 46.4A for at least an hour (and lower currents for longer periods) without coming to any harm.Our cooker is rated at 11KW and on a 32A RCBO, a clamp meter has read >40A for periods of 1/2 hour or so which I'm not that comfortable with ...
Although necessarily probabilistic (hence no certainties/'guarantees'), the concept of diversity nearly always works well. Were that not the case, then, for example, DNOs would be having constant problems with their LV distribution networks, with their cables 'melting' and their substation fuses blowing all the time
Kind Regards, John