[RE-wrenches] Rapid Shutdown for Off-grid systems

[Ray]

  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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