Point of Interconnection 690.64

[solarama]

We installed a small (30 module) system on a commercial building, to supply power to the parking garage, whose bill is paid by the owner. An existing 100 amp load center serves the garage and is supplied by a 40 amp main, and has its own meter. We brought the source feeder from the roof to a 30 amp fused disconnect (with 20 amp fuses), located adjacent the load center, and with a splice can between them. We brought #2 copper in a new conduit from the service main to the splice can. We resupplied the load center with #2, and made a #6 tap to the fused disconnect with 4 feet of wire. In my opinion this conforms with the requirement in 690.64 that "each source be interconnected at a dedicated circuit breaker or fusible disconnect". The inspector took exception, claiming the "point of interconnection" is the tap, not the fused disconnect, and wants instead for us to provide another panel subfed from the existing to provide space for a circuit breaker to land our source circuit. My position is that the tapped disconnect is simply a way of extending the bussing of the load center, and is no different from what he wants. I believe the key word is "dedicated", meaning that one should not combine more than one source at a splice or tap, before landing them at the disconnecting means. Think of it this way: If one had a gutter, with 100 amp rated conductors, and three fused disconnects serving three loads, each tapped from the gutter, then added our source circuit from our disconnect at a tap in the gutter, would this not comply with the code?

 

[jaggedben]

I agree with you.

The key word is 'dedicated', and the point of that section is that there should not be loads connected to the same branch circuit, or different kinds of power generation equipment. The purpose of the section is not to get semantic about where the connection point is.

Your best argument might be to point out that he is requiring you to use a circuit breaker when the code explicitly mentions that you can use a fusible disconnect. Also point out that the title of that little subsection is "Dedicated Overcurrent and Disconnect" (not "Point of Connection" and that your fusible disconnect supplies both. Appeal to higher authority if possible (contact John Wiles, or Bill Brooks, or SolarPro mag).

Good luck.

(BTW, the term 'source circuit' has a very specific definition in the NEC, referring to DC PV circuits. I would get out of the habit of using 'source circuit' when 'inverter output' better describes what you mean.)