Author: derek the solarboi

This update, two more racking manufacturers join the fold! Both EcoFasten and TerraGen have been added to the site, and there are interesting things to discuss about both. Let’s get into it.

---

First, let’s talk about TerraGen, because they’re actually the most overdue to be added to the website. Until I discovered Pegasus’ listing, I hadn’t been looking at CSA Group for UL 3741 listings – just about everyone’s listings were through Intertek. However, while Pegasus made the splash recently for having no approved vendor’s list, allowing any inverter or SID listed to 1741 to be used, they were not the first ones to achieve that goal. That prize goes to TerraGen, back in March of this year.

All of TerraGen’s rackings, TGR, TGT and TGP, are listed with any electrical equipment or inverters certified to UL 1741. More importantly, it’s extremely clear that this is how they’re listed. Their installation addendum explicitly calls this out in their Approved Components section, which is a contrast to Pegasus’ fairly confusing method of simply not specifying any inverters or SIDs (aside from mentioning specific instructions if using Tesla equipment). Here’s the exact wording:

• Approved electrical equipment / Inverters that:
  • Are UL 1741 listed
  • Must have PVRSS/PVRSE functions certified by UL 1741
  • Follow the installation locations and guidance of this addendum

This seems to me to fulfill the requirement of UL 3741 that says the devices associated with the PV Hazard Control System must be identified. Pretty neat. This seems to be a pioneering move by the CSA Group laboratories, in particular. Schletter seemed to get their listing with CSA before CSA started taking this tactic, but there’s a pattern brewing now, with first TerraGen, then Pegasus, relinquishing the micromanagement of specific inverter/SID testing.

---

EcoFasten also joins us, with ye olde, time-tested method of approving specific devices for their ClickFit and RockIt rackings. They’ve listed Tesla Powerwalls and inverters, plus Tesla’s MCI-1, but added another contender to the UL 3741 ranks, MidNite Solar’s MNSSR-600S-SS, paired with Solis inverters.

It’s a string isolation device, just like Tesla’s, but it’s SunSpec-enabled, meaning compatibility could be extremely easy for other inverters to adopt, since most inverters these days are listed with SunSpec MLPEs for module-level rapid shutdown. Because of this, I wouldn’t be surprised to see this device start getting quickly adopted by other inverter manufacturers, or potentially white-labeled to other brands. Either way, I’m getting excited for what might get introduced at RE+ in Anaheim this year.

---

Speaking of which, yes, I’ll be at RE+, so feel free to let me know if you want to meet up for a walk ‘n talk or show me some product! I won’t be updating The UL 3741 Reference until after RE+, just because I’ve got a ton of “real work” to get done between now and then.

Obligatory plug to throw money my way if you’d like to support the website, and if you want this news in your inbox in the future, sign up for the free newsletter!

As a personal note, if you enjoy all this nerdery, you should keep an eye on solarboi.com. I’ve got an opinion piece about UL 3741 just burning in my soul right now, and since I’m trying to keep the updates to this site limited to giving context about the products that get added, vs industry news or opinion pieces, any of that writing will happen over on the solarboi blog. I’ve got an RSS feed there as well, if you like to keep track of things that way.

Stay shiny,

derek the solarboi

Leave a Comment

There’s a lot of updates coming, including new Unirac and EcoFasten listings, but Pegasus has done something unprecedented— they say their new UL 3741 listing is valid for any inverter listed to 1741. For more, check out this blog post on solarboi.com.

Oh nooooo, pleeeeease don’t make this website obsolete Pegasus

Leave a Comment

No new announcements from manufacturers, but I think I’m now finally caught up with existing listings! Added inverters from Solis, Delta, and Growatt, as well as shingle systems from GAF Energy and Certainteed, along with a new “eBOS” category for MidNite Solar products.

I’ll put the short-n-sweet outline of new and changed things first, but stick around for some commentary afterward, because there’s some interesting implications with these updates.

---

New/Improved

• Added tooltips to the website! If you see a colored, underlined word, you can hover over it with your mouse to understand how I’m defining those terms.
• NEW – Solar shingle products
  • GAF Energy‘s Timberline shingle product
  • Certainteed‘s Solstice shingle product
• New inverters
  • Delta‘s M Series inverter (4-10kW)
  • Growatt‘s MIN inverter (3-11.4kW)
  • Solis‘ 3.6kW and 5kW version of the 1PxxK-4G-US inverters
• NEW – eBOS category
  • Two products from MidNite Solar, the MNPV6-WS and MNSST-Dual
  • Two products from Delta, their MCI and the Smart RSS
  • Changed ALPE term to “eBOS” for the Tesla MCI-1.
• NEW – Solar Structure category
  • This is a catch-all term for flush mount and ballast racking, as well as solar shingle systems. Basically anything that involves attaching or securing solar modules to a roof
• Fixed – A bunch of inverters weren’t showing up for the Chiko CK-AR railing page
• Improved – Cleaned up formatting for racking and inverter pages to make things more uniform and readable. More to do here, but it’s a start.
• Change – Inverter and Racking Manufacturer pages in the sidebar are now just one page named “All Manufacturers”, that breaks out into Solar Structure, Inverter, and eBOS manufacturer categories

---

What’s important?

When I discovered there are solar shingle systems with UL 3741 listings, it was a bit of a wild moment for me, because I never once gave a thought to how they were complying with the code. I assumed they had some method of rapid shutdown for each module. But as I thought about it, of COURSE they’d be extremely motivated to get UL 3741 listings; as a result, they’ve been innovating behind the scenes, out of the line of sight of the “mainstream” solar industry.

When Ironridge released their listing with the Tesla inverter/Powerwalls/MCI, the idea of a string-level rapid shutdown felt brand new, since the entire industry just puts inverters right next to the array in a ballast mount setting, to fulfill the voltage cutoff within a foot of the modules. At that time, I couldn’t find anyone else who was making a string-level interrupter; most everything out there is single or dual-module only, for the purposes of 2017 module-level shutdown. I was just looking in the wrong place.

GAF Energy and Certainteed both have UL 3741 solutions in place with string-level shutdown. GAF exclusively lists a series of Delta inverters, and two rapid shutdown devices that can handle up to 600v, the MCI and the Smart RSS, which seem to only work with Delta inverters. Certainteed has multiple inverters listed, but uses an entirely third party string-level shutdown from MidNite Solar, via a SunSpec-enabled rapid shutdown combiner. Theoretically this would physically work with any SunSpec-enabled inverter, but the listing requires MidNite’s SunSpec transmitter (that’s just a fun artifact of how listing things works).

I’ve had companies ask me if I knew of anyone else that made string-level shutdown devices, and I had to shrug my shoulders, point at Tesla, and say “Eh, maybe they’ll license that?” It’s just nice to know there’s already existing options like MidNite Solar’s solution that could easily be adapted to any inverter.

Btw, big shoutout to Duncan Cleminshaw of GAF Energy, who helped me through understanding how solar shingles comply with the code, as well as sending over some datasheets I couldn’t find. You da man! 🤙🏻

---

Terminology

As a result of throwing solar shingles in the mix, along with more of what I’ve been calling “ALPEs”, or Array-Level Power Electronics, I needed to rethink some categorizations. It didn’t feel right to add “shingles” or “BIPV” as yet another top-level category, and now that I had more “ALPEs” in the mix, I wanted to find a category that was somewhat recognizable by the industry.

“Solar Structure” is the term I’ve landed on to encompass “racking” and “shingles”. While it still feels awkward to me, it seems like the least wordy way to collate those two categories, while still being adequately descriptive.

“eBOS” is the term I decided to use instead of my home-grown “ALPE” term, meaning “electrical balance of system”. BOS is pretty common in the industry, and feels fairly understandable.

However, since those are both terms that I don’t hear being widely used, I added tooltips throughout the website! On certain terms that I feel may not be immediately understandable, you’ll see the words colored green and underlined by dots. Hover over them and you’ll get the site definition for them so there’s no confusion.

Eventually, I’ll probably completely redo my terminology to adopt more standard industry terms via Orange Button, but I just haven’t had the time for that yet.

---

What’s next?

While I’ve done some reformatting to structure and inverter product pages, I feel like I still have work to do there. I’d like to have more quickly readable information on each page, such as specifically noting that an inverter is single or 3-phase, DC and AC voltage ranges, etc. I’m open to suggestions about what information you’d find helpful!

Like I noted above, I want to adopt open standards for the taxonomy of this site, but that’s gonna be a lengthy process to figure out and will likely take some time. But I’m all about promoting industry standards that will make all our lives much easier.

I’ll probably add some more pages that are complete lists of various categories on the site. I did, actually, redo the Inverter Manufacturers and Racking Manufacturers pages in the sidebar to be just one manufacturers’ page, but I’d like to do some more of those for people who just want to see huge lists of things to get a sense of what’s out there.

I mean, there’s always gonna be stuff to tweak. If you want to stay up to date on the latest, feel free to subscribe to the RSS feed, or subscribe to the newsletter!

And, as always, if you’ve read this far, consider tossing a coin to your witcher! I’m very happy to provide this website for free, and it’s truly wonderful to me that so many people are finding this to be useful, but it’s just li’l ol’ me doing hosting/design/upkeep. You can buy me a coffee (or 4) if you’d like, and thank you in advance!

solarly yours,
derek the solarboi

Leave a Comment

Updates as of 4/8/24

Thanks to everyone for trying things out and sending feedback! I’ve been getting feedback from people, adding my own tweaks here and there, and making the site more responsive and usable.

First, and foremost, everything is actually at UL3741.com now. My initial plan was to have the site live at ul3741.solarboi.com, and use UL3741.com as a redirect, but that ended up being more confusing for people, and caused some weird issues. Now everything lives at UL3741.com, and ul3741.solarboi.com redirects to it!

I’ve added some links to the landing page, to better explain what the 3741 listing is for people newer to it: Ryan Mayfield’s article (for the people who wanna read stuff), and my own video (for those who wanna watch stuff).

New products and manufacturers:

• Added Ironridge‘s Aire railing
  • Ironridge has gotten their Aire railing freshly certified with UL 3741, too! This brings yet another option for sloped roofing, though the listing is still limited to Tesla products.
• Added Chiko USA and their CK-AR railing system for sloped roofs.
  • I’m still fairly light on details in terms of documentation for this — Chiko still doesn’t have anything about this on their website, but I’ve received enough info from them directly that I’m comfortable adding them to the list. Definitely make sure you get documentation from them before designing your system (which is the disclaimer for everything on this site, but, you know)
  • I haven’t seen anything about ALPEs rated for use with this system, so as far as I know, you still need to mount any listed inverters on the roof next to your array. Still useful for things like agricultural, or other large sloped commercial roofs.
• Added Opsun‘s Sunrail railing
• Added Solis 1PxxK-4G-US inverters. These are 6-10kW inverters.
• Added GoodWe MS-US30 inverters. These are 5-11.4kW inverters.

Finally, other tweaks and fixes, here and there.

• I fixed an issue where the lists on some inverter and racking pages were limited to 10 products
• Cleaned up the sidebar a bit
• Added a Contact page, for suggestions and subscribing to updates.
• Oh yeah, by the way, I added a newsletter! I plan to send out updates at max 1 per week, so visit that contact page if you’d like to get those updates to your inbox.
• If you don’t want to go the newsletter route but don’t want to rely on algorithms for updates, you can always just subscribe to the RSS feed.

If you find this helpful and want to support this project, please donate! All of the hosting, coding, etc is done by me and me alone in my spare time, so any support is greatly appreciated. 💜

Let’s stabilize solar together!

derek the solarboi

Leave a Comment

Welcome to UL3741.com! This launch includes two main categories: racking and inverters. There’s some additional subcategories as well, including what I’m calling the ALPE (Array-Level Power Electronics) from Tesla (MCI-1), as well as breaking out categories for flat roof solutions vs sloped roof solutions.

There’s certainly many more things to add to the list – some inverter manufacturers and racking manufactures alike, but also, I’m discovering that some solar shingles have UL 3741 approval.

Look forward to continued updates, and if you want to be notified as significant updates occur, please use the form below to sign up for the email list.

Leave a Comment