Isolated phase service entrance conductors

[sigmapsi]

We had a project where the utility required isolated phase construction for a 2500a, 480V service.

What they wanted was that the parallel 7 sets of conductors had to be run separated by each phase to the service disconnect.

I never heard of this, and had to research the NEC to verify that was even legal.

The utility rep really did not have a good answer when I questioned the purpose. (they stated this way all three phases may not be lost if one leg faults and melts the conductor).

Does anyone know why this would bw an advantage to the utility?

 

[REDDOG]

See: A) Article 300-20 induced currents in metal enclosure or raceways.
B) Article 310-4 parallel conductors.

Easier to terminate, cables do not cross each other.

If underground is it in PVC?
How is the system grounded?
How do you penatrate metal service equipment?

 

[sigmapsi]

yes, the requirement was to run PVC underground. there ia an artical in the nec for isolated phase conductors. penetrating the service gear enclosure required cutting sots between the conduit hole cutouts in the enclosure, or removing a square section if I remember correctly.