Rapid shutdown options

[solarken]

There has been more activity this past year with patent infringment lawsuits brought by Tigo. I have read that APSmart and one or two other RSD manufacturers have licensing agreements with Tigo, but SMA does not. And Tigo has challenged the Sunspec Alliance itself as to ignoring patent protection they believe they have in creating the standard. It looks like some of this is still working thru the courts. So it may be that soon either we will be more limited in RSD choices or they may become more expensive if sompanies like SMA are forced to pay license fees to Tigo.

 

[electrofelon]

Help me understand that one?

The person I talked to said the UL 3741 was more expensive enough than other options to make it not worth it. Maybe he had some specific situation that made it not work in that case, I don't know any details. You seem to be saying it's the same price. I have not investigated it myself. I admit I'm a little reluctant to believe you just because if that was the case wouldn't hardly anyone be using module level shutdown anymore?

It seems like the labor is pretty minimal just mounting a module on the back of the panel, it's plug and Play obviously.

 

[BackCountry]

The person I talked to said the UL 3741 was more expensive enough than other options to make it not worth it. Maybe he had some specific situation that made it not work in that case, I don't know any details. You seem to be saying it's the same price. I have not investigated it myself. I admit I'm a little reluctant to believe you just because if that was the case wouldn't hardly anyone be using module level shutdown anymore?

It seems like the labor is pretty minimal just mounting a module on the back of the panel, it's plug and Play obviously.

The reason hardly anyone is doing it is because the UL standard wasn’t published until December 2020 (https://www.sma-sunny.com/us/when-i...ior-choice-for-commercial-rooftop-pv-systems/)

Then, it took until 2021 for companies to actually get their racking and inverter combos listed (https://www.mayfield.energy/blog/ul3741?format=amp)

There is no cost difference, all of these racking materials that are listed weren’t built to UL3741, they were just tested and certified — they existed before and after the standard.

Some people still do RSD MLPE’s if they’re using SolarEdge as an example, no option not to.

But for SMA, CHINT, or any other larger inverter — UL3741 is absolutely the only way to go. That’s one less device to fail, two less connectors to not be seated, and a lot less labor.

 

[electrofelon]

The reason hardly anyone is doing it is because the UL standard wasn’t published until December 2020 (https://www.sma-sunny.com/us/when-i...ior-choice-for-commercial-rooftop-pv-systems/)

Then, it took until 2021 for companies to actually get their racking and inverter combos listed (https://www.mayfield.energy/blog/ul3741?format=amp)

There is no cost difference, all of these racking materials that are listed weren’t built to UL3741, they were just tested and certified — they existed before and after the standard.

Some people still do RSD MLPE’s if they’re using SolarEdge as an example, no option not to.

But for SMA, CHINT, or any other larger inverter — UL3741 is absolutely the only way to go. That’s one less device to fail, two less connectors to not be seated, and a lot less labor.

yes I know it is quite new.

If there is no cost premium for the 3741 systems, then certainly I am sold. Ill look into it more.

 

[BackCountry]

yes I know it is quite new.

If there is no cost premium for the 3741 systems, then certainly I am sold. Ill look into it more.

None at all. All of the major ballast systems are either UL3741 or in the process of doing it

IronRidge BX is rebranded Sollega, same product they’re both listed

Unirac’s ballast is UL3741

And PanelClaw is also (my personal favorite)

You’d likely be using one of those products anyway — super easy to meet the listing requirements and avoid however many hundred or thousand extra failure points that do no good. The firefighter safety concept makes sense in residential, in commercial it’s not very practical.

 

[pv_n00b]

There are a couple of downsides to 3741 listed systems that some people might find unworkable.

• Inverters have to be within 1' of the array so no central inverter racks. Inverters will be in the array all over the roof.
• Subarrays have to be within 2' of each other or there has to be some way to RSD the connecting conductors. While I have seen proposals for how this might be done, so far I have not seen anything in the field. Some layouts will just not be able to get the subarrays that close together.

 

[electrofelon]

There are a couple of downsides to 3741 listed systems that some people might find unworkable.

• Inverters have to be within 1' of the array so no central inverter racks. Inverters will be in the array all over the roof.
• Subarrays have to be within 2' of each other or there has to be some way to RSD the connecting conductors. While I have seen proposals for how this might be done, so far I have not seen anything in the field. Some layouts will just not be able to get the subarrays that close together.

Oh interesting, thanks. The second point would be a deal breaker for these roofs, there are lots of interruptions

 

[ggunn]

Oh interesting, thanks. The second point would be a deal breaker for these roofs, there are lots of interruptions

Another limitation might be the 150' limit on an array size in either direction without a pathway of 4' or 8' depending on how you implement it.

 

[BackCountry]

Oh interesting, thanks. The second point would be a deal breaker for these roofs, there are lots of interruptions

Yes, you for sure have to have a layout that’ll work. Works great for big flat roofs that you can navigate around.

If that doesn’t work, then I’d stick with SMA and use their RSD boxes over SolarEdge any day of the week.

 

[ggunn]

Yes, you for sure have to have a layout that’ll work. Works great for big flat roofs that you can navigate around.

If that doesn’t work, then I’d stick with SMA and use their RSD boxes over SolarEdge any day of the week.

FWIW, we switched from SMA to SolarEdge largely because of RSD issues.

 

[BackCountry]

FWIW, we switched from SMA to SolarEdge largely because of RSD issues.

For sure, we shy away from SolarEdge because they force you to use optimizers (I’d say 50% of our business is ground mounts) and clearly they’re not needed in that application. Likely, because of comfortability, we try to stick with SMA for everything.

That being said, they do make some nice sized inverters in the small commercial sector.

I don’t like how their network connectivity works, SMA has better results (for me) there. And I’ll say this… besides SMA’s terrible wifi connectivity, they are otherwise bulletproof.

 

[solarken]

For sure, we shy away from SolarEdge because they force you to use optimizers (I’d say 50% of our business is ground mounts) and clearly they’re not needed in that application. Likely, because of comfortability, we try to stick with SMA for everything.

That being said, they do make some nice sized inverters in the small commercial sector.

I don’t like how their network connectivity works, SMA has better results (for me) there. And I’ll say this… besides SMA’s terrible wifi connectivity, they are otherwise bulletproof.

FWIW, I disagree that SMA is bulletproof. I had to replace boards in multiple SMA Core1 inverters 2 years ago as part of a large number of failures SMA had, and had to replace a failed Core1 last fall. And my experience has been that SMA reimbursement to installers for warranty covered labor is awful. They thake forever, and the last check I got was drawn in a German bank and I can't deposit it. Still no response from SMA.
I think SMA is fast becoming a dinosaur of the industry, unless they turn things around.
I agree that optimization is often not needed for ground mounts, but it sure is nice to design with the string length flexibility that SolarEdge gives, and they continually innovate in all they do, unlike SMA.

 

[pv_n00b]

FWIW, I disagree that SMA is bulletproof. I had to replace boards in multiple SMA Core1 inverters 2 years ago as part of a large number of failures SMA had, and had to replace a failed Core1 last fall. And my experience has been that SMA reimbursement to installers for warranty covered labor is awful. They thake forever, and the last check I got was drawn in a German bank and I can't deposit it. Still no response from SMA.
I think SMA is fast becoming a dinosaur of the industry, unless they turn things around.
I agree that optimization is often not needed for ground mounts, but it sure is nice to design with the string length flexibility that SolarEdge gives, and they continually innovate in all they do, unlike SMA.

SMA was all about supporting the US market when it first came over here but that support has become begrudging at best. I've lost count of the number of conversations I've had with their engineers over getting support for US requirements that end in the engineer saying they don't need it for Europe so they are just not going to do it. SMA makes a great product, for the EU market. We can make it work in the US, most of the time.

 

[BandGap1.1eV]

There are a couple of downsides to 3741 listed systems that some people might find unworkable.

• Inverters have to be within 1' of the array so no central inverter racks. Inverters will be in the array all over the roof.
• Subarrays have to be within 2' of each other or there has to be some way to RSD the connecting conductors. While I have seen proposals for how this might be done, so far I have not seen anything in the field. Some layouts will just not be able to get the subarrays that close together.

3741 is a re-brand of the 2019 rapid shutdown requirement of 1' from the array boundary, only now with manufacturer specific assembly requirements. Good f'ing luck explaining that to an inspector

The Sollega solution is infuriatingly stupid. It requires (emphasis, REQUIRES) the use of plastic zip ties and disallows using stainless wire clips for wire management. Anyone who's been in this industry for 1 year will know plastic zip ties will break and leave your conductors in contact with things and surfaces they should not be contacting.

 

[pv_n00b]

3741 is a re-brand of the 2019 rapid shutdown requirement of 1' from the array boundary, only now with manufacturer specific assembly requirements. Good f'ing luck explaining that to an inspector

The 2017 NEC is the first to mention a listed option for RSD compliance. In 690.11(B)(2) it says it has to be listed as a rapid shutdown PV array. But the actual standard calls it PV hazard reduction, which is in the 2020 NEC. It makes it an AHJ judgment call to allow the use of a UL 3741 listed array to satisfy the 2017 NEC 690.11(B)(2) requirement but I have not heard of any pushback on this.
My guess is that the components that manufacturers specify to get the 3741 listing of their racking are not going to be time-tested contractor favorites since there is usually a glaring lack of field experience on manufacturing teams.

 

[pv_n00b]

Just an FYI, while I was at RE+ in Sacramento I put together this list of manufacturers with UL 3741 listed racking.

• IronRidge
• PanelClaw
• Sollega
• Unirac

I think Unirac is the first one to list a metal racking to 3741.

 

[Zee]

Not liking Solaredge past 2 years due to reliability and horrible customer support.

On a 60 kW job, installed SMA inverters with AP SMART (RSD-S-PLC) RSD Devices with great results.
Ie no failures that I know of.

Current product to use w SMA:
"JMS-F , Sunspec Compliant Shut Down Module - shipping with 12 WEEK LEAD TIME - plan way ahead" $32.80

 

[BandGap1.1eV]

The 2017 NEC is the first to mention a listed option for RSD compliance. In 690.11(B)(2) it says it has to be listed as a rapid shutdown PV array. But the actual standard calls it PV hazard reduction, which is in the 2020 NEC. It makes it an AHJ judgment call to allow the use of a UL 3741 listed array to satisfy the 2017 NEC 690.11(B)(2) requirement but I have not heard of any pushback on this.
My guess is that the components that manufacturers specify to get the 3741 listing of their racking are not going to be time-tested contractor favorites since there is usually a glaring lack of field experience on manufacturing teams.

Tying the requirements to specific products just silly IMO as the manufactures will have to constantly keep testing and certifying as they roll out new SKUs. Plus it completely negates the purpose of rapid shutdown, which is to reduce the voltage within the array to specific limits so fire fighters can shred the system with an axe or saw while they ventilate the roof.

For the record, I'm against MLPEs. In my world, module level rapid shutdown would never be a thing. It takes the perceived danger imposed on fire fighters, make it a real danger and shifts it to installers who now have thousands of extra connections and components on a roof that are potential locations of failure. How many optimizers have you replaced?

 

[pv_n00b]

Tying the requirements to specific products just silly IMO as the manufactures will have to constantly keep testing and certifying as they roll out new SKUs. Plus it completely negates the purpose of rapid shutdown, which is to reduce the voltage within the array to specific limits so fire fighters can shred the system with an axe or saw while they ventilate the roof.

I don't think it does negate the purpose. The purpose of adding RSD was to make the PV array safer for firefighters to interact with. The first attempt was simplistic, drop the voltage down and it will be safe. Even though there is no actual data saying 80V is safe. That voltage was chosen because it was assumed that no single module used on a roof-mounted system would have a Voc over 80V in the near future. The long-term solution was always the UL Listed PV array, but it took years for UL to put that together and now it's taking years for manufacturers to implement it. It's a long game. But keeping PV arrays the way they were was not an option, and UL Listed arrays are better than MLPE.
As for tying the requirements to specific products, that already happens with all the UL Listed equipment already in PV, modules, inverters, DC combiners, etc. Adding PV arrays to that list is really no different than the other equipment.

 

[ggunn]

I was in a session about this (along with other things) in the NABCEP conference a couple of days ago. The presenter talked about all the changes to the RS rules over the past few code cycles, and that he had discussed it with many firefighters. I asked the question of when firefighters approach a burning building that has a rooftop PV system, what will they assume is the situation? What code cycle was the PV array built under, which (if any) RS protection does it have, and if it does, is it working like it is supposed to? Or would they just assume the worst case scenario, that there is no RSD installed and functional. He answered that they would probably assume the worst.