A/C Wiring after the Inverter Must Be Outside?

Z

zemingduan

Senior Member
Location
Philadelphia,PA
Occupation
Electrical Designer
It is a 4-story multi-family building with solar panels and inverters on the roof. The PV system A/C disconnect will be located on the exterior wall next to the building electrical service equipment/disconnect and utility meters. After the PV A/C disconnect, the A/C wiring will run inside the building to the indoor house panel and interconnect with the system at the house panel.

My question is that, does NEC requires the A/C wiring between the inverter to the PV system A/C disconnect to run outside the building? Can you run it inside? If yes, do you need additional disconnect at the entrance point?

Thanks!
 
zemingduan said:
My question is that, does NEC requires the A/C wiring between the inverter to the PV system A/C disconnect to run outside the building?
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I think its important to define what these conductors are,
In the code the article 690 kinda ends at the inverter and article 705 takes over as it covers one or more electric power production sources operating in parallel, so the PV part I dont think matters after the inverter. Those conductors are either feeder conductors or service conductors depending on how the installation is done under article 705. And it has some variations based on code cycle. Generally speaking there is no hard and fast rule that those conductors must be outside, but if/when they happen to be service conductors, the all the rules for service conductors apply.
 
There is no requirement for PV system conductors to be outside, and never has been. There's no requirement for a disconnect at point of entrance for AC conductors.

There are some wiring method restrictions for DC conductors run inside. It used to make a difference to those requirements if you had a disconnect, but that rule was taken out. Anyway, that never applied to AC.

As tortuga said, if conductors happen to also count as service conductors, there are some restrictions. But it sounds like you are interconnecting through a breaker in the house panel, so that doesn't apply.
 
Thanks for the information. The A/C wiring after the inverter is feeder. But I think some AHJ will require a disconnect switch at entrance point a feeder feeding the building. This is kind of a grey area? Most inverter doesn't have an integral A/C disconnect.

I think some utilities require the PV A/C disconnect outside the building next to the service disconnect and utility meter. Is that true?
 
zemingduan said:
I think some utilities require the PV A/C disconnect outside the building next to the service disconnect and utility meter. Is that true?
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Yes, that is true in just about every jurisdiction I have worked with no matter if the PV system is line or load side connected, though some will grant a variance for placing the PV AC disco somewhere else outside the building besides at the service point.
 
zemingduan said:
Thanks for the information. The A/C wiring after the inverter is feeder. But I think some AHJ will require a disconnect switch at entrance point a feeder feeding the building. This is kind of a grey area? Most inverter doesn't have an integral A/C disconnect.

I think some utilities require the PV A/C disconnect outside the building next to the service disconnect and utility meter. Is that true?
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If the AC circuit were going to a separate structure the then it would need a disconnect to deenergize the structure from the grid per Article 225. But in the same structure that doesn't apply.

The point of disconnects is to deenergize conductors. A grid-tied inverter that drops voltage without a grid connection doesn't need disconnects at both ends of a feeder to accomplish that. You might run into an unreasonable AHJ who is confused by the word 'supply' and the direction of power flow, so I can't make any guarantees, but that kind of interpretation is rare and out of date in my experience.
 
jaggedben said:
If the AC circuit were going to a separate structure the then it would need a disconnect to deenergize the structure from the grid per Article 225. But in the same structure that doesn't apply.

The point of disconnects is to deenergize conductors. A grid-tied inverter that drops voltage without a grid connection doesn't need disconnects at both ends of a feeder to accomplish that. You might run into an unreasonable AHJ who is confused by the word 'supply' and the direction of power flow, so I can't make any guarantees, but that kind of interpretation is rare and out of date in my experience.
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Nonetheless, and irrespective of NEC requirements, many POCOs require an external PV AC disconnect.
 
Thasts how I read it also, inverter output.
Is it safe to say in a DC PV system 'inverter output' conductors no longer fall under 690 and thats where 705 takes over?
 
tortuga said:
Is it safe to say in a DC PV system 'inverter output' conductors no longer fall under 690 and thats where 705 takes over?
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No.

If you look at 2023 NEC 690.1 Scope, it covers "PV Systems", and per the definition in Article 100, that means "the total components, circuits, and equipment up to and including the PV system disconnecting means . . ." So the AC conductors between the inverters and the PV system disconnecting means are covered by Article 690. Article 705 takes over on the non-PV side of the PV system disconnecting means.

Cheers, Wayne
 
jaggedben said:
Yeah but he already has that. He's asking if he needs an additional disconnect where the inverter output from the roof enters the building. Or at least that's how I read it.
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I was addressing his question: "I think some utilities require the PV A/C disconnect outside the building next to the service disconnect and utility meter. Is that true?" It's true.
 
tortuga said:
Thasts how I read it also, inverter output.
Is it safe to say in a DC PV system 'inverter output' conductors no longer fall under 690 and thats where 705 takes over?
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I used to argue that but a couple cycles ago they messed with the definitions of PV system conductors and now it's harder to argue. 🤷🏻‍♂️

Theoretically inverter outputs can be from any DC source and therefore shouldn't be covered by 690 (except maybe in some solar specific instances). But that's not the way the code has always been written. That said, many 690 requirements only apply to DC conductors when you read carefully.
 
Since PA is on the 2020 NEC I'll take my answers from that version.
My question is that, does NEC requires the A/C wiring between the inverter to the PV system A/C disconnect to run outside the building?
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The NEC does not require the AC wiring described in this project to be run outside the building.
Can you run it inside? If yes, do you need additional disconnect at the entrance point?
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Yes, you can run it inside as described for this project. NEC 690.13 requires a disconnecting means to isolate the PV system wiring from the existing building wiring at the point of common coupling, which is the house service panel in this instance, and the disconnect can be the CB. NEC 705.20 requires a readily accessible disconnecting means. So a disconnect at the house panel inside the building may not be considered readily accessible by the AHJ and an additional disconnect outside required.
Now this is just NEC requirements, other AHJs such as the utility can apply their own requirements which could result in the need for additional disconnects.
Some of these requirements were changed in the 2023 NEC.
 
pv_n00b said:
NEC 705.20 requires a readily accessible disconnecting means. So a disconnect at the house panel inside the building may not be considered readily accessible by the AHJ and an additional disconnect outside required.
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Such an opinion by an AHJ would be illogical. 240.24(A) requires circuit breakers to be readily accessible. So if the panel breakers don't violate 240.24(A), using one of them as the 705.20 disconect wouldn't violate 705.20(3).

Cheers, Wayne
 
wwhitney said:
Such an opinion by an AHJ would be illogical. 240.24(A) requires circuit breakers to be readily accessible. So if the panel breakers don't violate 240.24(A), using one of them as the 705.20 disconect wouldn't violate 705.20(3).

Cheers, Wayne
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Maybe not, but most (all?) of the AHJs I have dealt with require a PV AC disco lockable in the OFF position outside the building where they can get to it to turn off and lock the PV system if they want/need to. Some of them also require that solar contractors add an external service disconnect if there isn't one already.
 
ggunn said:
Maybe not, but most (all?) of the AHJs
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Since you use that term to cover POCOs as well (as several of them are municipal in your area), sure they can add extra requirements. But my point is that the requirement is not in the NEC. Any AHJ tasked only with enforcing the unamended NEC would be wrong to enforce such a requirement.

Cheers, Wayne
 
wwhitney said:
Since you use that term to cover POCOs as well (as several of them are municipal in your area), sure they can add extra requirements. But my point is that the requirement is not in the NEC. Any AHJ tasked only with enforcing the unamended NEC would be wrong to enforce such a requirement.
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Where would one find an AHJ so tasked? I have never encountered one. :D

BTW, I clearly stated that these are AHJ requirements, not NEC.
 
wwhitney said:
No.

If you look at 2023 NEC 690.1 Scope, it covers "PV Systems", and per the definition in Article 100, that means "the total components, circuits, and equipment up to and including the PV system disconnecting means . . ." So the AC conductors between the inverters and the PV system disconnecting means are covered by Article 690. Article 705 takes over on the non-PV side of the PV system disconnecting means.

Cheers, Wayne
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Interesting take thanks, dang thats odd dont you think? I do see in the 2026 690.13 just points to 705 though,
Are inverter output conductors of a PV system are any different than inverter out conductors of any other system? Say Wind or a DC battery or generator source ? My take is chapter 6 is for specific equipment, and the specific equipment of a PV system might include the inverter but not feeders after it, inverter output conductors are simply feeders.
 
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