[RE-wrenches] Rapid Shutdown for Off-grid systems
Christopher Warfel
cwarfel at entech-engineering.com
Tue Feb 1 13:39:54 EST 2022
Hi, If I put a disconnect switch within one foot of the ground mounted
array, I am pretty sure this would comply with RSS requirements? Chris
On 2/1/2022 12:06 PM, 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.peltz at gmail.com]
> *Sent:* Tuesday, February 1, 2022 6:07 AM
> *To:* william at 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 <william at 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:jerrysgarage01 at 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
> <william at 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
>
> Miller Solar
>
> 17395 Oak Road, Atascadero, CA 93422
>
> 805-438-5600
>
> www.millersolar.com <http://www.millersolar.com/>
>
> CA Lic. 773985
>
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--
Christopher Warfel
ENTECH Engineering, Inc.
PO Box 871, Block Island, RI 02807
401-466-8978
<http://entech-engineering.com>
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