hi something strange came up on todays elecsa assessment. my job had a garage suply fed via a spare way in the consumer unit which fed a 5 way garage consumer unit. Now the CPC was sized using the adiabatic equation correctly. He mentioned that as the supply circuit was feeding a C.U with more than 2 ways the cpc in the supply cable was classed as a main earthing conductor and may be undersized, shock horror how can this be,. i then told him how its size had been calculated and he said no more and that it was fine. didnt really understand why the cu having more than 2 ways would make any difference, as the fault current would be dependent on the zs of the supply cable, and we size cpc's and main earthing conductors either by ref to table or via calculation. cant find anything in section 54 bs7671 with reguards to what he was talking about . anyone heard of this ??