Here you go, help me understand this.
I have an installation that has me wondering why the code is the way it is. I am hoping you can shed some light on this to help me understand the code.
Customer owned primary service feeding a transformer outside and by using PVC they intend to bond the XO at both locations. The grounding electrode connection will be located at the service rated transfer switch inside the building. The transformer secondary output is 4,000 amperes at 277/480 volts. The phase and neutral conductor are 10 sets of 600 kcmil. Since we need to provide an equipment bonding jumper per 250.30(A)(2) it is to be sized based on 250.102(C) based on the derived phase conductors. In a parallel installation the conductor is based on the size of the conductors in each raceway. Which would be 1/0 in each raceway.
Here is what makes me feel strange.
A 4,000 amp feeder (10 Paralleled Sets using 600 kcmil conductors) protected at their ampacity by an overcurrent device, 250.122(F) would require a 500 kcmil conductor in each raceway for an equipment grounding conductor.
With the installation I have that has unprotected feeder conductors from the transformer the equipment bonding jumper only needs to be a 1/0 in each raceway.
