msheets
PE Electrical
- Location
- Salt Lake City, UT, USA
- Occupation
- Electrical Engineer
I am assisting with some design questions on a largish ground-mount system. A question has come up regarding the size of the GEC at each row. We are using NEC 2020.
The support structure is a single-axis tracker with driven piles with ~11' embedment. Most rows hold 72 modules with 10 piles per tracker row. The piles in each row are bonded so that the piles are electrically continuous, and each row is bonded to a neighboring row through a CAB messenger wire. They have #8 CU wire from the inverter to the array, but that PV output circuit combines multiple strings which may not all be on the same row.
The Engineer of Record originally specified that a ground rod be driven at each tracker row, with #6 CU bonding the tracker pile to the ground rod. The installer is questioning this since each driven pile is already a grounding electrode, complying with 250.52(2), making the ground rod superfluous.
Per 690.47(B), the GEC should be sized per 250.66, but I'm not sure exactly how to interpret that for this type of system. None of the conductors are truly parallel, so do we size it off a single #8 CU, making the GEC #8 CU (probably #6 since it's exposed)?
The support structure is a single-axis tracker with driven piles with ~11' embedment. Most rows hold 72 modules with 10 piles per tracker row. The piles in each row are bonded so that the piles are electrically continuous, and each row is bonded to a neighboring row through a CAB messenger wire. They have #8 CU wire from the inverter to the array, but that PV output circuit combines multiple strings which may not all be on the same row.
The Engineer of Record originally specified that a ground rod be driven at each tracker row, with #6 CU bonding the tracker pile to the ground rod. The installer is questioning this since each driven pile is already a grounding electrode, complying with 250.52(2), making the ground rod superfluous.
Per 690.47(B), the GEC should be sized per 250.66, but I'm not sure exactly how to interpret that for this type of system. None of the conductors are truly parallel, so do we size it off a single #8 CU, making the GEC #8 CU (probably #6 since it's exposed)?