[RE-wrenches] RSS: Is it necessary?

Christopher Warfel cwarfel at entech-engineering.com
Tue Feb 18 13:30:36 PST 2025


Is there a NEC reference for that you know of?, as I see Romex brought 
down to switches very often, and I've not found a reference prohibiting 
that.  As far as a ground mounted solar system being climbed on, 
anything is possible, but hopefully trees are of more interest.  Thank 
you, Chris

On 2/18/2025 11:38 AM, Tyrone Houck wrote:
>
> My understanding of code is that all circuits need to be protected 
> from physical damage. It's the same with AC circuits in an unfinished 
> garage..can't have exposed romex under 8' in that scenario either.
>
>
>
> On Tue, Feb 18, 2025, 8:34 AM Christopher Warfel via RE-wrenches 
> <re-wrenches at lists.re-wrenches.org> wrote:
>
>     Well, I think if wiring of a ground mounted system looks like a
>     jungle gym, then something is wrong.
>
>     On 2/18/2025 11:32 AM, Glenn wrote:
>>     Rarely are AC electrical circuits and equipment placed adjacent
>>     to a residence in a cleared field where there may be children
>>     thinking it looks like a jungle gym either...
>>
>>     -Glenn
>>
>>     On Feb 18, 2025 11:23, Christopher Warfel via RE-wrenches
>>     <re-wrenches at lists.re-wrenches.org>
>>     <mailto:re-wrenches at lists.re-wrenches.org> wrote:
>>
>>         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:tyronehouck at gmail.com]
>>             *Sent:* Monday, February 17, 2025 8:59 PM
>>             *To:* william at 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
>>
>>             tyrone at oregonsolarworks.com
>>
>>
>>             On Mon, Feb 17, 2025, 8:42 PM William Miller via
>>             RE-wrenches <re-wrenches at 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-bounces at 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 at 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 at 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
>>                     <william at 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-bounces at 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 at 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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>>             _______________________________________________
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>>         -- 
>>         Christopher Warfel, PE
>>         ENTECH Engineering, Inc.
>>         PO Box 871, Block Island, RI 02807
>>         (401) 447-5773
>>
>>
>     -- 
>     Christopher Warfel, PE
>     ENTECH Engineering, Inc.
>     PO Box 871, Block Island, RI 02807
>     (401) 447-5773
>
>     _______________________________________________
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Christopher Warfel, PE
ENTECH Engineering, Inc.
PO Box 871, Block Island, RI 02807
(401) 447-5773
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