National Electrical Installation Standards

Standards as High as Your Own

Friday, May 27, 2022


Good Afternoon and thanks for your work in this forum. My application is a 480Y277 generator with an integral 2000/3-pole circuit breaker. There will be (11) sets of individual cables, #4/0 Type XHHW between the generator and transfer switch. The transfer switch will pick up the entire building load, i.e. premise and equipment. I am trying to determine the size and number of the ground conductor(s) required between the generator and the transfer switch. Can you help me out, please?

Pat Wolff



Hello Pat, thanks for participating. We'll answer the question based on the information provided. You use the term "ground conductor" and we will assume you mean "equipment grounding conductor." Session 250.122(F) requires where conductors are installed in parallel in multiple raceways, that the equipment grounding conductors shall be installed in parallel in each raceway. there are 11 raceways based on the question. Note the last sentence of 250.122(F)(1)(b) in the 2020 NEC, indicates that each equipment grounding conductor shall be sized in compliance with 250.122 based on the rating of the feeder overcurrent protective device. The equipment grounding conductor(s) required for this feeder installation in accordance with Table 250.122 (2000 amperes) is a minimum of 250 kcal copper.

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