[RE-wrenches] RSS: Is it necessary?

Mon Feb 17 21:25:20 PST 2025

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

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

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

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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