I think the 8' rule for this is a little bizarre. I can have ac circuits lower than 8' all through my basement, attic and so forth, but this barrier requirement for dc conductors that have robust jackets and no exposed live connections has been hard to justify.  Christopher Warfel

On 2/18/2025 12:25 AM, William Miller via RE-wrenches wrote:

Tyrone:

You raise an excellent point. Wire guarding is required on ground mount arrays <https://millersolar.com/MillerSolar/case_studies/18%20Wire_shielding_on_ground_mounted_PV_arrays/Wire_shielding_on_ground_mounts.html>, although the language is vague and the industry does not provide many hardware solutions.  Also, in our area the enforcement <https://millersolar.com/MillerSolar/case_studies/18%20Wire_shielding_on_ground_mounted_PV_arrays/SLO_County.html> of the code on this practice is non-existent.  I suspect this is true in many regions.  Improvements need to be made.

William Miller

Miller Solar

17395 Oak Road, Atascadero, CA 93422

805-438-5600

www.millersolar.com <http://www.millersolar.com/>

CA Lic. 773985

*From:*Tyrone Houck [mailto:tyroneho...@gmail.com]
*Sent:* Monday, February 17, 2025 8:59 PM
*To:* will...@millersolar.com; RE-wrenches
*Subject:* Re: [RE-wrenches] RSS: Is it necessary?

As far as ground mounted arrays are concerned there is one clear protection mandated by the NEC-the requirement for protection from physical damage for all conductors under 8'.. although this isn't as specific or redundant as rapid shutdown requirements, it typically means conduit or at least some kind of physical barrier with the intention often referenced as protection for children or other unqualified personnel. Not sure if that fits into the point you were making but it seems worth mentioning.

Sunny Regards,

Tyrone Houck

Oregon Solarworks LLC

CCB #204937 LRT #076

541-787-1366

tyr...@oregonsolarworks.com


On Mon, Feb 17, 2025, 8:42 PM William Miller via RE-wrenches <re-wrenches@lists.re-wrenches.org> wrote:

    Rebekah:

    Thank you for your post.

    I have looked at UL3741 over and over.  Here is what I have
    gleaned:  After module level RSS was mandated there was a
    reevaluation of what voltages were actually dangerous for
    firefighters to be exposed to.  It turns out 80 VDC is not
    dangerous and, given all of the circumstances for firefighters,
    exposure to voltages that are much higher is safe enough. For some
    reason I have not yet grasped, all of the components need to be
    matched and tested to achieve the hallowed UL3741 rating.

    Module level RSS would have presented a big enough upheaval in the
    industry if the equipment needed to comply was safe and reliable. 
    There is evidence that in many cases it may not be, and that
    amplifies the skepticism many feel about the current solutions,
    and frankly, any future solutions.

    It appears the code making panel, when writing the original module
    level RSS requirements, may have been a bit “chicken little” about
    the need for RSS. This presents a real credibility issue for code
    makers.  You are seeing that credibility problem reflected in the
    discussions here on this forum. Given the back-peddling, how can
    we understand and believe what is really necessary?

    Forgive me for being skeptical, but why is it that systems with
    components that have been tested together are demonstrably safer
    than any collection of high quality components installed carefully
    and competently?

    In my mind there is another disconnect here (pun intended):  I can
    put high voltage, arc producing and sustaining wiring on a
    residential roof or free-standing rack and not be required to
    protect that wiring in any specific manner.  If I were to install
    a 240VAC, over-current protected and de-energizeable air
    conditioning feeder without conduit, I would be red-tagged in a
    hot second.  It may be that fire-fighters in protective clothing
    can withstand voltage above 80VDC, but can children not wearing
    protective “turn-out” clothing?  Children mess around on roofs and
    underneath ground-mount arrays.  Why is the NEC not protecting
    them by mandating specific, listed and tested wire management and
    guarding systems?

    Thank you very much and I look forward to your reply.

    Sincerely,

    William Miller

    Miller Solar

    17395 Oak Road, Atascadero, CA 93422

    805-438-5600

    www.millersolar.com <http://www.millersolar.com/>

    CA Lic. 773985

    *From:*RE-wrenches
    [mailto:re-wrenches-boun...@lists.re-wrenches.org] *On Behalf Of
    *Rebekah Hren via RE-wrenches
    *Sent:* Monday, February 17, 2025 10:26 AM
    *To:* RE-wrenches
    *Cc:* Rebekah Hren
    *Subject:* Re: [RE-wrenches] RSS: Is it necessary?

    I read the wrenches post regularly, as does Brian Mehalic. We have
    both been on CMP-4  (responsible for Article 690) for the past
    three code cycles. I believe a few other CMP members probably read
    too. The International Association of Firefighters ("largest and
    most influential labor unions in North America") is represented on
    CMP-4 and yes they do have had a lot to say about this issue.

    This is definitely not the first time we have heard that certain
    RS devices are on balance causing more trouble than they are
    curing  - though on the other hand some manufacturers have
    certainly figured out how to make safe and effective MLPE.


    I'm a big fan of UL3741, I have been on that UL technical
    committee for about 5 years, and it is the best approach I see to
    expand both off-grid and grid-interactive solutions that don't
    require MLPE for RS. SMA for example is very present and working
    hard at revisions on that standard right now. At this point I
    can't see us having any luck in removing 690.12 requirements,
    except perhaps to replace the inside the array boundary voltage
    limit with only option as 3741 listing). So please keep asking
    manufacturers (inverter/rack) to pay attention to UL3741 and
    design products to meet the standard.

    Best

    Rebekah

    Licensed Electrical Contractor
    NABCEP Certified Solar PV Installation Professional™ 091209-85

    Tel: 336.266.8800

    On Mon, Feb 17, 2025 at 10:59 AM Amos Post via RE-wrenches
    <re-wrenches@lists.re-wrenches.org> wrote:

        Seems like there has been talk of rescinding RSD requirements
        before on this forum.  It also seems that it might gain some
        traction if a dedicated group of installers spoke up to the
        right people (Code Making Panel for instance) and put some
        time into it.   I agree that at the very least we need
        reliable RSD equipment, and my preference would be less vs more.

        Does anybody know if any sort of RSD is being required in
        Europe (not that we follow their electrical codes/ideas…just
        curious)???



               Amos Post
           Integrity Energy
          W 802.763.7023
           C 802.291.2188
        ienergyVT.com <http://www.ienergyvt.com>

        Facebook <https://www.facebook.com/integrityenergyllp?ref=hl>

        On Feb 17, 2025, at 12:30 PM, david quattro via RE-wrenches
        <re-wrenches@lists.re-wrenches.org> wrote:

        It seems anecdotal until it happens to you.

            My mention of civil disobedience has been answered clearly
        with a “No” in this forum, and I'm fine to hear that.

           I'll clarify a few points as to why I honestly think RSD
        has been a huge and costly mistake. I genuinely think RSD
        requirements should be terminated immediately. If the
        technology were more robust and if it worked consistently I
        wouldn't protest. But *all* the products I've tried have been
        trouble.

           William, respectfully your analogy to seat belts is not an
        appropriate comparison to Rapid Shutdown. Seat-belts were
        required in all new cars starting in 1968 because there was
        statistical evidence supporting their tremendous efficacy in
        saving human life. Currently seat belts save about 15,000
        lives per year.

        Contrasting to RSD: was implemented because of the following
        paranoid fairytale scenario - “A firefighter is on a burning
        solar roof in the daytime, and wearing a metal axe at their
        hip. the poor guy/gal falls into live solar glass, and
        shatters it. The fall is so forceful that the heavy-duty
        fireman’s suit is punctured. Electricity conducts through the
        axe blade, through the suit, contacts the skin, and a DC
        circuit is completed through their body.”

           As far as I know, this has never happened once anywhere on
        earth. Let’s be honest - this scenario has an incredibly low
        chance of ever happening in all the future of humanity. So
        considering that RSD has never helped anyone yet, and probably
        never will... How many fires can be attributed to RSD? How
        much property damage has occurred because of these fires?

        The best path to safety for firefighters is by preventing fire
        disasters in the first place.  Fires spread. Any fire that
        happens endangers property owners, tenants, business owners,
        neighbors, shoppers, bystanders, nearby forests, etc.  RSD
        manufacturers aren't doing a good job right now, so we are
        seeing low quality unreliable electronics on the roof. I will
        stick my neck out and admit that installers are not always
        perfect. Humans make mistakes - sometimes in initial
        construction, and sometimes during repair and maintenance
        (i.e. when hunting down failed RSD's which happens far more
        than it should).

           At this time, these devices are not being designed to
        withstand reality. When problems happen, manufacturers are
        quibbling. They ignore you until you go away, or until you sue
        them.

          This level of "safety" is not important, and in fact RSD is
        causing fires every year.

        On Sat, Feb 15, 2025 at 11:38 AM William Miller
        <will...@millersolar.com> wrote:

            David, Ray:

            I have not had any problems with the Tigo RSS equipment I
            have installed and I have had minimal problems with
            optimizers and micro-inverters (which are also RSS
            equipment).  Apparently others have had failures.  We
            don’t know statically how serious this problem is—the
            posts here are purely anecdotal.

            We also have not heard from the other side of the debate:
            the fire fighters.

            Based on lack of verifiable information I can not
            personally conclude that RSS is all problem and no benefit.

            To declare that the concept is flawed because the
            equipment available is not reliable is like saying we
            should not be required to install airbags because a bad
            batch of them was manufactured.  We are seeing problems
            with the equipment needed to implement a safety
            requirement.  That observation does not logically conclude
            the safety requirement is not valuable.

            I hesitate to dismiss any safety requirement out of hand.
            Safety systems are designed to save lives and protect from
            injury, and most of them do. I am glad to have anti-lock
            brakes, smoke detectors and air bags.   I have also found
            it quite handy to initiate RSS to allow me to work more
            safely on solar circuits.

            Does anyone on this installers forum have contacts in the
            fire-response community that can comment on the their side
            of the issue?  If RSD is really necessary for safety, then
            I will do my best to install good equipment properly and
            hold manufacturers accountable for shoddy solutions.  If
            RSD is not that effective we need to discuss undoing the
            code requirements.

            Sincerely,

            William Miller

            Miller Solar

            17395 Oak Road, Atascadero, CA 93422

            805-438-5600

            www.millersolar.com <http://www.millersolar.com/>

            CA Lic. 773985

            *From:*RE-wrenches
            [mailto:re-wrenches-boun...@lists.re-wrenches.org] *On
            Behalf Of *david quattro via RE-wrenches
            *Sent:* Saturday, February 15, 2025 6:05 AM
            *To:* RE-wrenches
            *Cc:* david quattro
            *Subject:* Re: [RE-wrenches] Tigo inverter experience

            RSD is the worst thing to happen to solar. Has anyone
            considered civil disobedience?

                I wonder what would happen if all the installers
            banded together and refused, as a united industry
            ‘brotherhood.’ WE are the ones stuck with the bullshit in
            the aftermath.

                 I’m not being snarky here , this a genuine question
            to the group:   Does anyone have _good_ experience with
            RSD?   i.e. you’re really glad RSD was there, and you
            genuinely feel safer?  you’re glad and happy to comply
            with this code and you look forward to continuing to use
            RSD for the rest of your career?

            On Fri, Feb 14, 2025 at 3:40 PM Ray Walters via
            RE-wrenches <re-wrenches@lists.re-wrenches.org> wrote:

                it seems silly that we are required to install these
                extra pieces of equipment for added "safety", that are
                actually a fire hazard on the roof.  Just to survey
                again: how many homes have been saved by RSD?  How
                many fire fighters have actually actuated the RSD
                system, so that they could hack through the array to
                vent the roof?

                I think it should only be required if you have covered
                so much of the roof with PV, that the fire dept can't
                access uncovered roof to do their venting.  The whole
                premise of RSD is flawed.  IMHO, its just another
                effort to block the wider adoption of solar.

                When it comes to off grid, RSD causes such a decrease
                in reliability to amount to a decrease in safety, due
                to possible loss of communications, water, and heat. 
                Add the fire hazard and RSD is really not making our
                customers' lives better.

                Ray Walters
                Remote Solar

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