?
Wednesday, November 29, 2023
Question:
Hello CQD, what size grounding wire is required in each PVC for the following runs:
- 2-parallel runs of 4-750 MCM Aluminum conductors installed in a 4-inch PVC
- 4-parallel runs of 4-500 MCM Aluminum conductors in 4inch PVC
Also, how many ground rods are required at the building these feeders are supplying?
The electrical engineering said number #6 AWG equipment ground, and 2-ground rods. Thanks, Patrick Kunc
A
Answer:
Hi Patrick, thanks for participating in the CQD. The equipment grounding conductors for each of the parallel sets is required to be fully sized based on the overcurrent protection device as specified in Section 250.122(F) and Table 250.122. Based on the conductor sizes provided, the maximum ampacity and OCPD for each paralleled feeder would be:
- For the 2-sets of 750 MCM Aluminum conductor the ampacity would be 520A, protected by a 600A OCPD, requiring a 2/0 Aluminum equipment grounding conductor in each of the raceways in accordance with Section 250.122(F)
- For the 4-sets of 500 MCM Aluminum conductors the ampacity would be 560A, protected by a 600A OCPD, requiring a 2/0 Aluminum equipment grounding conductor in each of the raceways in accordance with Section 250.122(F).
The buildings supplied by these feeders would require a grounding electrode system in accordance with Sections 250.32, 250.50, and 250.52. If ground rods are used for part of the grounding electrode system, then 2-ground rods would be needed, unless a single rod complies with the Exception to Section 250.53(A)(2).