Art. 690.64 (solar photovoltaic point of connection)

[rsparks]

Art. 690.64 requires, among other things, that load center busbars be protected at their ampacity (or at 120% of their ampacity for a dwelling unit), taking into consideration that total available current = panel main or feeder rating plus "back-fed" solar system over-current device rating. In the case of a single load center, the requirements are clear. Ambiguity arises when a photovoltaic system is connected at a subpanel. There is an argument in print contending that, for example, a 15A back-fed solar circuit in a 100A sub panel makes the 100A feeder to that panel a 100A back-fed circuit to the next panel back towards the service. I would argue that compliance with art. 690.64(B)(2) at the "point of connection" satisfies the requirements of the article, without consideration to "upstream" circuit components. Any thoughts?[/url][/code][/quote]

 

[George Stolz]

Re: Art. 690.64 (solar photovoltaic point of connection)

There is an argument in print contending that, for example, a 15A back-fed solar circuit in a 100A sub panel makes the 100A feeder to that panel a 100A back-fed circuit to the next panel back towards the service.

Can you post a link to this argument? What exactly is the argument? A subpanel is likely to be smaller (or the same size of) the panel supplying it. Why would someone worry that the subpanel is fine, but the panel supplying that panel might be undersized? That doesn't make sense.

In terms of grounding and bonding, I would imagine the subpanel approach would be more cumbersome than having the two systems interact at the utility service, where grounding electrode conductors are already present. But difficult doesn't entail "illegal."