Rapid shut down 2014 NEC 690.12 requirement and ground-mount system

[M.B.]

I am installing a grid-tied ground-mounted 7500W PV system. The AHJ annotated my permit with a sticker that says: "RAPID SHUT DOWN AND LABEL REQUIRED PER ART. 690.12 AND 690.56(C)."

Everything that I can find about the requirements of 690.12 discuss roof-mount systems, PV-related circuits (and primarily DC wiring) within the house, and firefighter safety. My inverter will be at the ground-mount PV array, some 300+ feet of underground buried (AC) cable away from the house. The AC disconnect mounted at the house will serve to totally disconnect all solar PV system related supply immediately upon dropping that switch. While there will be about 10 feet of AC cable within the house associated with this system (i.e., between that exterior mounted and labeled AC disconnect and my load center panel in the basement), that can be isolated from the entire solar power supply by dropping the AC disconnect.

In my estimation, my remote-ground-mounted array/inverter and AC disconnect at the house meets the requirement of 690.12. I'm looking for others' thoughts on the matter before I call up the AHJ to discuss... I note that my county only adopted the 2014 NEC a few months ago, so I anticipate the plan reviewers and inspectors are learning the ins-and-outs of interpreting this new requirement, too.

Assuming I am correct, I am also a bit confused about the application of the labeling of 690.56(C) - "PHOTOVOLTAIC SYSTEM EQUIPPED WITH RAPID SHUTDOWN".... while the AC disconnect effectively has an immediate shutdown for the PV-related wiring inside the house to the panel, it isn't a "rapid shutdown" in the sense of the 690.12 requirement, and the inverter and equipment out at the array are still energized.... so do I put that sticker on the AC disconnect or not?

[Sunking]

Two Golden Rules.

1. Inspector is always correct.
2. When Inspector is wrong refer to rule 1.

[M.B.]

Sunking - I absolutely understand and abide by those Golden Rules. I'm just looking for some affirmation of my understanding prior to discussing with AHJ, as I anticipate s/he may need some thinking and suggestion to determine what s/he understands to be correct, especially considering that this provision of the code is quite new to his/her jurisdiction (only a couple of months). And, it's likely that mine is the first ground-mount installation under the 2014 NEC, since the vast majority of our county's population lives in 0.1ac lot dense suburbian neighborhoods, and thus any PV s/he sees is almost exclusively roof-mounted.

[emartin00]

The rapid shutdown requirements still allow high voltage within 10 feet of the array. If your inverter is located at the array, then it should automatically comply as the AC disconnect will shutdown the inverter output immediately.
In addition, 690.12 only applies to arrays that are on or within a building. If your array is located away from any structure, it is not required to comply.

[Naptown]

That distance is a long way for the AC to go without having huge cables or voltage rise to the inverter to make it trip off.
Have one here in Maryland starting in a week or so that is a ground mount and is subject to the 2014 code. The rapid shut down only applies to systems mounted on a building. In that case we are mounting the inverter just inside the wall of the basement with DC terminating within 5' of point of entry. This has been approved by the AHJ.

[M.B.]

Naptown: the inverter (SunnyBoy 7700TL-US) is rated at 32A AC output, so circuit is sized for 40A, and back-fed into 200A load center (at opposite end of bus from service entrance). Underground cable spec'd out at #2 Aluminum - but due to both local product availability and adding an extra margin of conservatism, upsized the cable to #1.

Spoke w/ the plans reviewer this morning, and he agreed that the AC disconnect at the house would meet 690.12.

[Naptown]

The #1 will just get you under 2% drop

[Sunking]

Naptown: the inverter (SunnyBoy 7700TL-US) Spoke w/ the plans reviewer this morning, and he agreed that the AC disconnect at the house would meet 690.12.

That maybe true. But as Rich will tell you refer to rule #2.

[radareclipse]

What about putting the Inverter at the garage/house? Put a DC disconnect at the array, because you have DC coming off of that. Wouldn't that be better than trying to run AC current all that distance?

[Naptown]

That maybe true. But as Rich will tell you refer to rule #2.

Yes been there done that to no avail
Been doing some systems for the county.
Amazing how helpful when you are working for the AHJ.

[M.B.]

Just circling back... turns out the inspector was great! He didn't question the rapid shutdown, and without me asking acknowledged that the ground mount system doesn't require that in the same way as roof mount with energized DC cables "on or in the building". He was very thorough, as I am the homeowner doing the entire install of my system. In the end, he congratulated me on how well it was all put together and done per code. It took the utility company almost a month to come set the new meter, which was a rather anti-climatic 3 minute job, and we are now officially running on solar!