In this picture the two banks of 4" towards the back are utility secondaries. I am taking the picture at about the corner of where the transformer will be. Obvious is the difference in length of the two duct banks. One of the requirements for this utility on a service of this size is a six foot separation between ductbanks. The reason is for heat dissipation. I initially had the conduits running together because it is such a short run it was impractical to obtain the required 6ft separation but was made to do this by the big boss at the engineering Dept. Maybe they don't understand how parallel conductors operate. (Granted they will probably only pull conductors in three of them anyway) Do other utilities have this requirement around the country? They must not have problems with it or they wouldn't keep up this practice.
"Where run in separate raceways or cables, the raceways or cables shall have the same physical characteristics.
Conductors of one phase, neutral, or grounded circuit conductor shall not be required to have the same physical characteristics as those of another phase, neutral, or grounded circuit conductor to achieve balance."
Joe Tedesco, NEC Consultant
Re: Parallel Conductors#15492 10/19/0210:30 AM10/19/0210:30 AM
All phases are not required to be all of the same length, for example, All of Phase A can be 15 feet, all of Phase B can be 17 feet, all of Phase C can be 19 feet, and all of the neutrals can be 23 feet.
Lengths for these SEC's all depends on the overall length of the run --- to the service point at the overhead or lateral.