Inverter replacement options for a legacy Sunpower positive-grounded array

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  • mountaindrifter
    Junior Member
    • Jul 2020
    • 2

    #1

    Inverter replacement options for a legacy Sunpower positive-grounded array

    Hey SPT, long time lurker, here with some brain damage I am hoping to find an solution to!

    Typical scenario is a ~14yo sunpower system that has a failed SMA -12 that needs to be replaced. The modules are legacy, positive grounded, sunpower mods in good condition. I am interested to know what you all have been doing out there to replace the inverter on a positively grounded array now that everything has gone transformerless. I have seen other companies go as far as to replace the entire array, but seems there must be some other option I am unaware of. Without sounding cocky, I am quite involved in the industry so I am really beating my head against the wall on this one.

    In the past we would normally find an old new stock transformer based SMA or Fronius inverter to replace the faulty one with. over the last few years it has been getting difficult to find these out dated inverters. This is of course not a sustainable option.

    Maybe there is some solution I have not encountered yet with a MLPE device? I know that SolarEdge optimizers do not work with positive grounded mods. While the Tigo works with positive grounded systems, it does not convert or add isolation in any way so the inverter issue remains. As far as I know the IQ line enphase micros do not work with a grounded mod. With the way I understand it, there is not a way that a MLPE device that would solve the issue.

    I know there are some string optimizer devices such as the SPOT that can add galvanic isolation, but these are cumbersome and expensive. The Galvo was a decent option, but it is small and is now also no longer being made.

    So I wonder, what are you all doing out there for this scenario? Are there any good transformer based inverters available or something else you are doing to replace an inverter on a positively grounded array? It isnt the last time we will deal with it and it will only come up more as there were quite a few Sunpower installers in my area back then and these inverters are begining to age now.

    btw, I saw the other similar post a couple days ago oddly enough but this is unrelated and a different question. Thanks in advance for your help!
  • badwithusernames
    Member
    • Jun 2020
    • 44

    #2
    I am one of the cheap suckers thats recently built a system using Sunpower panels, because they were essentially free. I've researched this pretty extensively and could not find anything current that will work with them. There are a few guys that have used a DC/DC transformer in some way to achieve the galvanic isolation, but the forum threads always dead end without any conclusion. I did end up finding a few places that have some of the SB-3000/4000/5000/6000/7000Us as surplus inventory; I purchased two of the SB4000us for my 7kw system. Pretty sure they have several more. If you could use 3 of them, PM me and I will give you their contact info. There were also several open box or nos on Ebay last week.
    SD

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    • mountaindrifter
      Junior Member
      • Jul 2020
      • 2

      #3
      Thanks @badwithusernames thats basically been my experience. I thought I would try over here to see if there was some solution I have not yet heard of. I have looked into some of the devices for adding the galvonic isolation but so far the ones I have seen have been either so bulky or costly that replacing the array itself was not much different in cost. Especially now that modules are so inexpensive. If the cost between a DC/DC converter and replacing the array is close, it makes more sense for the future to deal with the array now. It is just unfortunate for the industry to eventually tell so many people that they will need to replace their entire array to replace the inverter.

      EDIT: I would be interested to know what distributor you found that had some more old new stock. Doesnt seem like I can PM you, maybe because of the new account.
      Last edited by mountaindrifter; 07-08-2020, 03:53 PM.

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      • Mike90250
        Moderator
        • May 2009
        • 16020

        #4
        PM's have been disabled because of a few bad actors abusing them . Sorry
        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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        • badwithusernames
          Member
          • Jun 2020
          • 44

          #5
          email me for info. sddesignbuildATgmail

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