Is solar inverter output connection to a SUB-panel permitted?

[yeknom]

690.64 (B) (2008 NEC) permits connection "at any distribution equipment on the premises". Can this be a sub-panel. Consider a barn with panels on the roof, can I connect (assuming other code conditions are met) to a a breaker panel in the barn, or do I need to bring the PV generated power, via a separate feeder, back to the house where the utility service disconnecting means is located?

There seems to be some ambiguity in the code which speaks of the inverter output being "connected to the load side of the service disconnecting mean" but then that connection can be "at any distribution equipment on the premises" (with some additional conditions). What is the meaning of this phrase "at any distribution ......" and why is it put in the code?

Can panels on the roof of a 9 story building connect via inverters to a breaker sub-panel on the roof, presently used solely to distribute power to the elevator motor? (assuming, of course, that requirements 1-7 of 690.64(B) are met?)
That would be a dramatic saving in costs if a separate new riser for the PV system is not required.

 

[Flex]

Ive seen subpanels on a roof for the the PV. Id say its ok but would like to hear what others say.

 

[davedottcom]

The location of the panel isn't an issue.

The size of the PV Inverter as well as the Ampacity ratings of the panel & the conductors will determine if it's permitted or not. & yes 690.64(B) 1 through 7 apply

 

[davedottcom]

690.64 (B)

There seems to be some ambiguity in the code which speaks of the inverter output being "connected to the load side of the service disconnecting mean" but then that connection can be "at any distribution equipment on the premises" (with some additional conditions). What is the meaning of this phrase "at any distribution ......" and why is it put in the code?

.

It's basically saying you can backfeed in any panel you want to (After the service disconnect) as long as the conditions are met. All of the "sub-panels" or distribution equipment are already on the "Load side" of the service disconnect. I don't think it's ambiguous at all, I think they made a point to mention "any distribution equipment" to make it clear that the main panel was not the only option.

 

[yeknom]

Davedottcom,

So the meaning of my quoted parts of 690.64 is that the inverter output, that is ELECTRICALLY connected to the load side of the service disconnect, can be PHYSICALLY attached (connected) at any distribution equipment on the premises (if, of course, the other required conditions are met)?

 

[ty]

yes.......

 

[davedottcom]

You got it!

 

[szrom]

690.64(B)(2) connection

690.64(B)(2) connection

I am an engineer in the PV industry. We regularly make load side connections to downstream subpanels by backfeeding a circuit breaker (or fused switch). Just wanted to add a few insights.

The so-called 120% rule in 690.64(B)(2) must be applied to the subpanel you connect to but also to all panel buses and feeders upstream to the utility connection. In addition, any panels or switches upstream not related to the "PV to utility" path which are tapped off of feeders must also have main overcurrent protection. This is to ensure the full utility current + PV contribution does not overload a tap. These requirements involve a detailed analysis of the distribution system.

 

[yeknom]

szrom, ty, davedotcom,

Great feedback. I am very impressed with the quality of perception of the key elements of the question and the very informative and direct response. And Szrom, thanks for your additional comments about the panel buses and feeders upstream. This was something I was wondering about and it was very helpful to get confirmation that my sense about the necessity for this requirement is correct. Thanks again.

 

[BillK-AZ]

Do not overlook the often required Utility Disconnect

Do not overlook the often required Utility Disconnect

While it is true that you may be otherwise able to connect 'panels on the roof of a 9 story building via the inverter to a breaker sub-panel on the roof, presently used solely to distribute power to the elevator motor', often this is not practical because the local utility requires an accessible disconnect switch.

I have installed PV systems on school buildings in Arizona at some distance from the service entrance. The utility (APS) required a plaque at the service entrance directing utility crews to the building and the ground mounted disconnect switch. A lockbox with a key for fence locks was required and needed to be explained on the plaque.