[RE-wrenches] Rapid Shutdown for Off-grid systems
Christopher Warfel
cwarfel at entech-engineering.com
Tue Feb 1 13:43:32 EST 2022
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.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
>>
>>
>>
>
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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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