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Will SE 300w power optimizers likely clip a 320-330w panel?

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  • Will SE 300w power optimizers likely clip a 320-330w panel?

    The Panasonic 325w panels were tested by California and rated at 306w PTC. I have a hot sunny roof when at peak production. Is a SE 300w optimizer likely to clip power from a 320-330w Panasonic panel on a hot sunny roof?
    If so, at most it would be for only a brief period and would this harm the optimizer?

  • #2
    Solaredge notes (somewhere) that optimizers can never be undersized, however inverters can, to a limit.

    As I understand, your panel STC should not exceed the "power" rating of the optimizer, 300w in this case.

    Also, they list two additional data points that most typical panels will not exceed, but unusual circumstances might such as: operating in extreme cold, being within a group of skyscrapers with additional sun reflections, etc. They are max open circuit voltage and max short circuit current that your panel supplies.

    For the P300, those are 48v and 11a. Even briefly exceeding 48v will destroy the optimizer, which is designed for 60 cell panels. If you have 72 cell, you don't want this one, as a cold day will likely kill the optimizer.

    All three values (STC watts, volts open circuit, and amps short circuit) can be found on the label on the panel, as STC watts, Voc, and Isc. Note that you should multiply Voc by 1.25 to get a rough worst case "really cold morning" open circuit voltage.

    The only exception I've seen to this is that STC watts can be exceeded up to 5w (305 in this case) due to some 300w panels being +/- 5 watts.


    • #3
      @NukeEngineer's comments made me do more google searching and yielded the follow statement from SE on oversizing inverters: "Oversizing of power optimizers is not allowed: Module STC as listed in the module datasheet must not exceed the power optimizer rated input DC power." Doing so would presumably void the optimizer's warranty. STC is always greater than PTC.
      While I think that it is very unlikely that my 325w panel production would ever exceed 300w, because my roof is always hot when it is sunny and my roof faces NE (~322 degrees), but production doesn't matter it is only STC rating that matter for maintaining one's warranty.
      Last edited by Steeler.Fan; 07-02-2018, 07:27 PM.


      • #4
        Hi Steeler.Fan,

        The P400 has been the recommendation for Panasonic 96-cell panels for the past few years. Though looking at SE's website it appears these are being discontinued and P500 is the new recommendation:

        But this is a recent change, likely many distributors still have the P400's in stock.

        Panny spec sheet



        • #5
          the P300 was NEVER recommended for a 96 cell Panasonic. You should be pairing with older P400, or more likely P500

          the panasonics can go up to 69.6V and the only optimizers rated for that are the P400 and P500
          OutBack FP1 w/ CS6P-250P