That was my understanding too, but the language Jay has from 2017 (and I
confirmed in 2020) reads different. I was positive ground mounted
arrays did not need to comply with RSS. The bogus argument made by the
businesses influencing the CMP, and by a few mercenaries supposedly
representing firefighter concerns was explicitly for roof mounted
systems going through its history. Chris
On 2/1/2022 1:11 PM, Ray wrote:
Ground mounts do NOT require RSS. We hashed this out years ago on
the Wrenches list, when NEC 2017 came out.
See Figure 690.1(B) Note (2): /" The PV system disconnect in these
diagrams separates the PV system from all other systems"./
Thus, the PV disconnect is defined as the transition point from the PV
system to all other systems, like battery or inverter systems. The
installer/ designer decides where to put that disconnect. I usually
put it on the wall before it goes into the building, and I have never
had an inspector question that.
Thanks,
Ray Walters
Remote Solar
303 505-8760
On 2/1/22 10:06 AM, William Miller wrote:
Jay:
Here is the text from 2017:
/690.12 Rapid Shutdown of PV Systems on Buildings. PV/
/system circuits installed on or in buildings shall include a rapid/
/shutdown function to reduce shock hazard for emergency/
/responders in accordance with 690.12(A) through (D)./
//
/Exception: Ground mounted PV system circuits that enter buildings, of/
/which the sole purpose is to house PV system equipment, shall not be/
/required to comply with 690.12./
The wording is interesting. The requirement is directed at “PV
system circuits…”, not PV arrays. The passage does not specify where
the PV feeding those circuits is located, it just addresses where the
circuits are, specifically “in or on a building.”
The only circuits that are exempt are those feeding a building that
serves only one purpose, to house PV equipment. For circuits that
enter building with other uses—homes, garages, barns, workshops,
etc.-- it would seem there is a requirement to have rapid shutdown
systems (RSS).
Reading through the rest of the section, I don’t see any language
that gets us out of the requirement to reduce voltages to less than
80 volts within 30 seconds inside the array boundary, as in module
level shutdown, regardless of roof-top or ground-mount. Although the
2020 code includes some differing language, I don’t see it as
exempting ground mount systems.
The moral of the story is this: For ground-mounts: either install
RSS or put your equipment (inverters, charge controllers, batteries,
BOS) in a separate building housing only that equipment.
I don’t necessarily like the requirement, but I think it exists.
Jay, or anyone, please, please tell me I am reading this incorrectly.
By the way, regarding battery circuits, here is a quote from a post
by Bill Brooks on March 16, 2016:
/In the 2017 NEC, we were very careful to carve out all batteries and
loads,/
/that were previously part of PV systems, and place them in their own/
/articles./
I have not read through the battery sections of the code to verify
this, I am taking Bill at his word.
William Miller
Miller Solar
17395 Oak Road, Atascadero, CA 93422
805-438-5600
www.millersolar.com <http://www.millersolar.com/>
CA Lic. 773985
*From:*Jay [mailto:jay.pe...@gmail.com]
*Sent:* Tuesday, February 1, 2022 6:07 AM
*To:* will...@millersolar.com; RE-wrenches
*Subject:* Re: [RE-wrenches] Rapid Shutdown for Off-grid systems
2017 code has a specific exception/clarification for ground mount
solar that it does not need RS.
It’s in the first line after 690.12
Jay
On Feb 1, 2022, at 12:13 AM, William Miller <will...@millersolar.com>
wrote:
Jerry:
Yes it is required. Rapid Shutdown: NEC 690.12. All buildings
except dedicated solar buildings. Read it and weep.
William
Miller Solar
17395 Oak Road, Atascadero, CA 93422
805-438-5600
www.millersolar.com <http://www.millersolar.com/>
CA Lic. 773985
*From:*Jerry Shafer [mailto:jerrysgarag...@gmail.com]
*Sent:* Monday, January 31, 2022 7:21 PM
*To:* William Miller; RE-wrenches
*Subject:* Re: [RE-wrenches] Rapid Shutdown for Off-grid systems
William
Are you sure RSD is required on a non habitable building,
historically its not required. Now that being said we use fire
raptor with the best results, yes it takes an extra conduite and
might require a button and power supply depending on inverter
application.
Jerry
On Mon, Jan 31, 2022, 9:57 AM William Miller
<will...@millersolar.com> wrote:
Friends:
It is quite rare for us to install off-grid systems on
roof-tops. We have one coming up with about 20kW on a large
barn roof. This will be our first off-grid with a
module-level rapid shutdown requirement. I see no exemptions
from RSS for off-grid systems in the code. I have looked at
the options and this is what I have found:
1.Fire Raptor
2.Tigo TS4-F
3.AC coupling with micro-inverters or optimizers
No one of these approaches seems ideal. The fire raptor
requires extra wiring for control leads. The Tigo requires a
wireless control system which worries me about reliability.
With AC Coupling systems floating the proposed AGM batteries
may be awkward. Furthermore, with AC coupled systems one
cannot charge batteries unless the mini-grid is operational,
a big problem.
Have any of you implemented module-level RSS on a
battery-based inverter system? I looked in the archives and
found no threads that apply. Thank in advance.
William Miller
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