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  • SMA rapid shutdown a POS

    I installed a 13kW system last June. Ever since then the panels and SMA 6.0 inverters have been working great. But, every few months or so the rapid shutdown boxes lose their mind and cut off energy to the grid ie, they totally shut down the array. The only thing that seems to bring them out of it is a full re-boot which means waiting over night. This really blows because it means that I'm not getting credit for energy produced during the shutdown time. I'm thinking about just bypassing all of that nonsense. Anyone else have the same situation?

  • #2
    Before you disconnect that protective feature I would get some measurements of the power quality coming into your home. It is possible that the POCO grid is having issues which unfortunately causes your inverters to shut down. What is surprising is that it takes a full reboot to get them working again which does not sound correct.

    Have you contacted your installer and let them know about the issue?

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    • #3
      The rapid shutdown boxes are on the panel (DC) side of the inverters so the problem isn't poco power quality. The inverter turns off because power from the array is disconnected by the errant rapid shutdown box. At night, the rapid shutdown boxes lose power and then reboot once the sun comes up and hits the array. All is well again now that it's a new day. It's just an annoyance when one of the rapid shutdown boxes basically blue-screens and cuts off the inverter it's attached to, thus missing out on energy that should have been produced. The only way to reboot it is to cut power from it ie; have the sun go down.

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      • #4
        Hmm, interesting issue. Have you gotten a resolution yet ?

        While my current code does not need rapid shutdown yet, I was thinking of being proactive and adding it with the install
        as the new code goes into effect in July 2018 for us.

        This seemed very promising and also not expensive - http://www.amerescosolar.com/sites/d...own%202015.pdf

        Also, how many panels/kw can a single shutdown box handle ?

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        • #5
          Originally posted by lanb View Post
          Also, how many panels/kw can a single shutdown box handle ?
          It can shut down two mppt channels. Each of those channels may have two strings (of equal length) combined in parallel. See here for more technical infomation.

          http://files.sma.de/dl/27991/RSS-Com...S-TI-en-10.pdf

          As for being proactive, I think this design will only be good for 2014 NEC. The requirements are tighter in 2017 NEC. If you want future proof, Solaredge or microinverters are a better choice.
          Last edited by sensij; 05-15-2017, 09:03 PM.
          CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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          • #6
            Thanks for the heads up. Can you point me to the 2017 NEC requirements ? Also, is there anyway a string inverter can comply with the 2017 requirements ?

            I am still not sold on the long term viability of Solaredge, hence the hesitation.

            Then there is also also the cost factor - the string + SMA is 10% cheaper

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            • #7
              Originally posted by lanb View Post
              Thanks for the heads up. Can you point me to the 2017 NEC requirements ? Also, is there anyway a string inverter can comply with the 2017 requirements ?

              I am still not sold on the long term viability of Solaredge, hence the hesitation.

              Then there is also also the cost factor - the string + SMA is 10% cheaper
              I understand the cost consideration... if it wasn't for the rapud shutdown requirement (2014 NEC is ineffect here in CA), I would probably have gone with a string inverter for the system I'm putting up now instead of SolarEdge. With rapid shutdown in the mix, the costs were much closer, enough that I though it worth paying to avoid the extra installation work that rapid shutdown requires.

              Here is more on 2017 NEC:

              After the public comment period, it was up to CMP 4 to decide how to proceed. After much deliberation - far more than for any other topic - CMP 4 combined the SEIA and fire service proposals and added language allowing for building-integrated glass or polymeric PV arrays with completely concealed wiring. The revised rapid-shutdown requirements in 690.12(B)(2) provide three compliance options for reducing hazards within a PV array.
              • Option 1: List and label or field-label PV array as a rapid-shutdown PV array.
              • Option 2: Limit control conductors within the array boundary to 80 V or less within 30 seconds of rapid-shutdown initiation.
              • Option 3: Install nonmetallic PV array with no exposed wiring and array more than 8 feet from any grounded metal parts.




              To implement Option 1, industry stakeholders need to develop a product safety standard for rapid-shutdown PV arrays. To allow time for this standard's development process, CMP 4 added a delayed adoption date, specifying that 690.12(B)(2) "shall become effective January 1, 2019." One benefit of codifying Options 2 and 3 is that these provide stakeholders with some guidance on developing a consensus for the rapid-shutdown PV array certification standard.
              CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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              • #8
                Thanks for the info on NEC 2017. I am guessing the solar companies would need to come up with a way to retrofit any string setup if they ever have to be rapid shutdown certified.

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                • #9
                  Originally posted by lanb View Post
                  Thanks for the info on NEC 2017. I am guessing the solar companies would need to come up
                  with a way to retrofit any string setup if they ever have to be rapid shutdown certified.
                  A lot of ground mounts are probably exempt. Bruce Roe

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                  • #10
                    I would say forget about future proofing anything. Once your system is installed to current code you are grandfathered in forever. If your current code does not require rapid shutdown then don't do it. It's just one more thing that may cause headaches and fail, not to mention the expense. All rapid shutdown does is cut D.C. voltage from getting from your array to your inverter. In my case that's like 20 feet in grounded steel conduit. Big deal. Most fire departments could care less about rapid shutdown.

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                    • #11
                      Originally posted by DaveDE2 View Post
                      I would say forget about future proofing anything. Once your system is installed to current code you are grandfathered in forever. If your current code does not require rapid shutdown then don't do it. It's just one more thing that may cause headaches and fail, not to mention the expense. All rapid shutdown does is cut D.C. voltage from getting from your array to your inverter. In my case that's like 20 feet in grounded steel conduit. Big deal. Most fire departments could care less about rapid shutdown.
                      Have you got you problem resolved? I'm about to install the same RS system on my array and naturally wonder. My system consists of 2 independent strings each feeding its own inverter so I'm forced to use 2 RS boxes on the roof, one per string. It sounds like you have more than 1 RS box as well. Have you noticed it's the same box causing the trouble or when it happens the entire array gets down so you wouldn't be able to tell?

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