So how bad are string inverters vs microinverters?

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  • nomadh
    Solar Fanatic
    • Sep 2014
    • 227

    So how bad are string inverters vs microinverters?

    From all the things I've heard for years this really blew my mind.
    I can rest easy now with my sma and won't bother to fixate on getting a tigos on that shaded corner.

  • Mike90250
    Moderator
    • May 2009
    • 16020

    #2
    without my sitting through yet another mindless fool tube episode, what do they say that is so mindblowing ?
    Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister

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    • nomadh
      Solar Fanatic
      • Sep 2014
      • 227

      #3
      Originally posted by Mike90250
      without my sitting through yet another mindless fool tube episode, what do they say that is so mindblowing ?
      He did a side by side comparison and even with some extreme shading there wasn't more than 2 to 3% difference. He does a good job with some graphs and worth the watch.

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      • Mike 134
        Solar Fanatic
        • Jan 2022
        • 393

        #4
        His testing did disprove the idea that one module shaded would drop the entire string down to its level. Since in my case I need to have rapid shutdown up at the module level might as well get optimizers.

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        • nomadh
          Solar Fanatic
          • Sep 2014
          • 227

          #5
          Originally posted by Mike 134
          His testing did disprove the idea that one module shaded would drop the entire string down to its level. Since in my case I need to have rapid shutdown up at the module level might as well get optimizers.
          I've been hearing a bit about this. What's the issue? Isn't a string inverter shut down fast enough?

          Comment

          • Mike 134
            Solar Fanatic
            • Jan 2022
            • 393

            #6
            Originally posted by nomadh

            I've been hearing a bit about this. What's the issue? Isn't a string inverter shut down fast enough?
            If you don't do the shutdown at the panel level then the wires under the panels can have 300-400 DC volts on them. A mis-swing with an axe while trying to save someone life or property venting the roof could cut those wires endangering the firefighter even more than climbing up onto a burning building's roof.

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            • SunEagle
              Super Moderator
              • Oct 2012
              • 15126

              #7
              Originally posted by nomadh

              I've been hearing a bit about this. What's the issue? Isn't a string inverter shut down fast enough?
              The Fire Departments have found that breaking the roof with a "live" solar array can be dangerous so the NEC has included the requirement of a shut down feature that kills the voltage within a few feet of the panel system.. As long as the voltage is below 50VDC then the First responders shouldn't be electrocuted if they cut into a "live" wire.

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              • nomadh
                Solar Fanatic
                • Sep 2014
                • 227

                #8
                Originally posted by SunEagle

                The Fire Departments have found that breaking the roof with a "live" solar array can be dangerous so the NEC has included the requirement of a shut down feature that kills the voltage within a few feet of the panel system.. As long as the voltage is below 50VDC then the First responders shouldn't be electrocuted if they cut into a "live" wire.
                So now we are looking to outlaw string inverters? Has a firefighter ever been electrocuted this way before?

                Comment

                • Mike 134
                  Solar Fanatic
                  • Jan 2022
                  • 393

                  #9
                  Originally posted by nomadh

                  So now we are looking to outlaw string inverters? Has a firefighter ever been electrocuted this way before?
                  Not at all but do need to add an additional piece at each solar module so that the voltage is limited to only what one module puts out. As to a firefighter getting hurt? Whether one has or not the code is being proactive to prevent it. After working 40 years hands on with electricity I can assure you codes are there for a valid reason, getting a rule into the NEC is not something done casually.

                  Comment

                  • SunEagle
                    Super Moderator
                    • Oct 2012
                    • 15126

                    #10
                    Originally posted by nomadh

                    So now we are looking to outlaw string inverters? Has a firefighter ever been electrocuted this way before?
                    Actually yes there have been some injuries due to energized solar arrays that fire fighters have tried to remove to save the building that was on fire. So I never said that string inverters are outlawed only that you now need to include "shutdown" equipment to adhere to the latest NEC which all AHJ's read and then determine what it means. So if you don't like what is now the rule then don't perform a DIY install or follow the rules.

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                    • oregon_phil
                      Solar Fanatic
                      • Jan 2019
                      • 497

                      #11
                      Originally posted by Mike 134
                      His testing did disprove the idea that one module shaded would drop the entire string down to its level. Since in my case I need to have rapid shutdown up at the module level might as well get optimizers.
                      It should be noted that the YouTube author used 120 cell half cut solar panels which can be much more shade tolerant than standard 60 cell panels. That being said, I have an SMA string inverter with TIGO optimizers on 60 cell solar panels and am very satisfied with my set up. I too needed rapid shutdown so why not just get optimizers.

                      Comment

                      • solar pete
                        Administrator
                        • May 2014
                        • 1816

                        #12
                        Originally posted by nomadh
                        From all the things I've heard for years this really blew my mind.
                        I can rest easy now with my sma and won't bother to fixate on getting a tigos on that shaded corner.
                        String Inverters rock

                        Comment

                        • J.P.M.
                          Solar Fanatic
                          • Aug 2013
                          • 14939

                          #13
                          Originally posted by solar pete

                          String Inverters rock
                          Pete: I agree, or at least I will until my string inverter craps out and there's no string inverter replacement to take the power from my 8+ yr. old Sunpower panels.

                          Legacy/Rebuilt string inverters are getting scarce. Any suggestions ?

                          Comment

                          • nomadh
                            Solar Fanatic
                            • Sep 2014
                            • 227

                            #14
                            Originally posted by oregon_phil

                            It should be noted that the YouTube author used 120 cell half cut solar panels which can be much more shade tolerant than standard 60 cell panels. That being said, I have an SMA string inverter with TIGO optimizers on 60 cell solar panels and am very satisfied with my set up. I too needed rapid shutdown so why not just get optimizers.
                            I wanted to add a few tigos to my system for shading and calling 5 places it seems no one even understands what I'm taking about . I was wondering if tigo went out of biz. Was it swallowed up by Smi?

                            about the 120 cell panels, so was he scamming to do that? You think using 60 cell would have been much worse?

                            Comment

                            • nomadh
                              Solar Fanatic
                              • Sep 2014
                              • 227

                              #15
                              Originally posted by SunEagle

                              Actually yes there have been some injuries due to energized solar arrays that fire fighters have tried to remove to save the building that was on fire. So I never said that string inverters are outlawed only that you now need to include "shutdown" equipment to adhere to the latest NEC which all AHJ's read and then determine what it means. So if you don't like what is now the rule then don't perform a DIY install or follow the rules.
                              the big advantage of the string inverter was cheaper and simpler, no electronics on the roof. If you need a module at each panel then you killed the string inverter market. In fact if someone wanted to do something like it it is in fact illegal you need what used to be a simple string inverter plus another 29 or 30 electronic breakable doodads on you roof causing problems.

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