if u dont understand diversity for cookers <SNIP> if u dont understand it dont do it
I do understand diversity, So your saying that the cooker itself won't allow all of it's elements to be on at the same time ? therefore limiting the maximum draw from the mains therefore it's safe to use a 2.5mm cable ?
Ok, then what size circuit breaker do you use then ?.
I know it's bad practice to quote yourself but ... What size circuit breaker would you use then ?
As far as the N conductor carrying 3 times the load as I think has been suggested, then if you look at a cooker as a resistive load, which it basically is then the vector sum of the 3 phase currents even at full load will not be the sum of the currents due to the "phase rotation" to put it in simple terms, that is the peak currents will be 120 degrees apart.
Yes, that makes sense, I'll bow to your superior knowledge.
Whilst the original issue of the cooker on the 2.5 is well off.
To size the supply for the new cooker, then there is a possibility that diversity can be applied, and, that the cooker will have inbuilt peak current limiting, perhaps simply by basic normally closed switches, that will only allow certain combinations of element to operate.
Perfect, so the cooker is in effect only a 5.5Kw device (240Volts x 23Amp) since that is the maximum it allows to be pulled off the mains at anyone time rather than the 9Kw that was originally quoted therefore a 2.5mm cable would be enough.
I hope I have got all that right.