pvgreeze
Member
- Location
- Philadelphia
- Occupation
- Electrical Engineer
Hello everyone, I'm curious to know if anyone has any thoughts/experience with a rooftop community solar installation and interpreting the needs for a common grounding electrode system per NEC 250.58. I've come across a number of high level designs where a community solar project is proposed on an existing building with its own service, but the community solar is interconnected either on the low voltage bushings of the existing utility pad mounted transformer or via a completely separate service and new pad mounted transformer. Therefore, while the building itself is shared, the community solar and the building distribution exist as completely separate services.
I personally don't think there is much ambiguity in 250.58; the PV system inverters and combiner panel ("ac system") is located "in or on that building or structure;" therefore, a connection must be made between the PV equipment grounding electrode system and the existing grounding electrode system. 250.58 specifically calls out "Where separate services...are required to be connected to a grounding electrode(s), the same grounding electrode(s) shall be used." 250.58 contains the language both "in or at a building or structure" and "in or on that building or structure" which is confusing, especially "at" versus "on," but, beyond just the legalese of the NEC, I think the intention is quite clear regardless.
Lastly, assuming NEC 250.58 requires that a community solar PV system be connected to the existing building grounding electrode system, I'm curious thoughts on the installation requirements mandated by 250.64 for the GEC. This scenario would presumably follow under 250.64(D), and the installation would need to fall under 250.64(D)(1/2/3). I would interpret 250.64(D)(2)(2) as allowing the GEC to connect the existing grounding electrode system to the PV grounding electrode system via the use of the EGC/EG busbar at any point in the PV system circuit, and not specifically at the service disconnect (covered by 250.64(D)(2)(1)). I am interested in this use due to the fact that a project I am reviewing has the service disconnect located across a driveway from the building, and tying the PV grounding electrode to the AC combiner panel would be far more practical, as that panel is located on the building.
Any thoughts or feedback is appreciate. Thanks!
I personally don't think there is much ambiguity in 250.58; the PV system inverters and combiner panel ("ac system") is located "in or on that building or structure;" therefore, a connection must be made between the PV equipment grounding electrode system and the existing grounding electrode system. 250.58 specifically calls out "Where separate services...are required to be connected to a grounding electrode(s), the same grounding electrode(s) shall be used." 250.58 contains the language both "in or at a building or structure" and "in or on that building or structure" which is confusing, especially "at" versus "on," but, beyond just the legalese of the NEC, I think the intention is quite clear regardless.
Lastly, assuming NEC 250.58 requires that a community solar PV system be connected to the existing building grounding electrode system, I'm curious thoughts on the installation requirements mandated by 250.64 for the GEC. This scenario would presumably follow under 250.64(D), and the installation would need to fall under 250.64(D)(1/2/3). I would interpret 250.64(D)(2)(2) as allowing the GEC to connect the existing grounding electrode system to the PV grounding electrode system via the use of the EGC/EG busbar at any point in the PV system circuit, and not specifically at the service disconnect (covered by 250.64(D)(2)(1)). I am interested in this use due to the fact that a project I am reviewing has the service disconnect located across a driveway from the building, and tying the PV grounding electrode to the AC combiner panel would be far more practical, as that panel is located on the building.
Any thoughts or feedback is appreciate. Thanks!