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, although the language is vague and the industry does not provide many hardware solutions. Also, in our area the enforcement 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
CA Lic. 773985
From: Tyrone Houck [mailto:tyronehouck@gmail.com]
Sent: Monday, February 17, 2025 8:59 PM
To: william@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
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
CA Lic. 773985
From: RE-wrenches [mailto:re-wrenches-bounces@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™ 091209-85Tel: 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
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 <william@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
CA Lic. 773985
From: RE-wrenches [mailto:re-wrenches-bounces@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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