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installation producing 3x less power and half the voltage

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  • installation producing 3x less power and half the voltage

    Hi,

    I have an older installation consisting of 2 independent but identical arrays installed in 2008. The problem: one of the arrays produces 3x less the power than the other (say ~5KWh vs 15KWh per day). I am new to solar so I need some "ropes" (or perhaps "cables" ).

    The arrays:
    - consist of 14 SPR-210 panels and dedicated SPR-3300 inverter in each.
    - have no shade and are mounted on the same rack (same angle and direction).
    - the inverters report 160-180V on bad array and 260-280V on the other array.
    - the inverters do not go online with lower voltage than ~170V (or there about) so I assume when it is in off-line state the reported voltage is a "no load" voltage of the array.
    - on bad array the voltage is usually <180V (the reported amps in off-line are 0.2A vs in on-line when in strong sunshine it could go up to 4A but still with low voltage).
    - when eventually both arrays go on-line (with more sunshine) the amps are also lower on bad array (afair about 4A vs 7A)

    I think:
    1) hence the panels are rated at ~40V and hence 7x40V=280V, each array is made up of 2 strings of 7 panels each
    2) the bad array low voltage in both the load and no-load state suggests that there is no high resistance in connections
    3) the bad array low voltage in no-load state suggests that at least 3 panels (280V-160V=120V=3x40V) in each of its strings would have to be off line (bypassed) for the voltage to be so low?
    4) per 3 above I'd have to have 6 panels down (3 in each string) but this is not very likely so I suspect one of the strings is completely off-line while the other is limping with just 4 active panels?

    Any comments or suggestions about how to diagnose this problem (and not get electrocuted )?


    Thanks!

    Michal



    Last edited by MichKrom; 07-10-2019, 02:47 PM.

  • #2
    I would start by disconnecting one of the strings on the bad side and see if the inverter
    will run on the other string, observe V and I. Then try the same on the other, this
    should give clues to the problem. If both read exactly the same, the inverter does
    become suspect, connect a non functioning string by itself to the other inverter. For
    safety all wiring to be done well after sunset, measurements the next day.

    If you find a string putting out much reduced voltage, you could take it all apart and
    measure the voltage of each panel. If they read normal, you will need to make a
    more dynamic, under load test. More later. Bruce Roe

    Comment


    • #3
      Something else that may work, use a thermal gun to find out of line temps after
      it is running best power. This found faults for me. Bruce Roe

      Comment


      • #4
        Thanks Bruce!

        With thermal gun measuring line temperatures what am I looking for? Active lines being hotter? Or for panels that are hotter/colder?

        Comment


        • #5
          Point it at panels and cells of panels, best results after some running in good sun
          has stabilized temps. You will see that the good strings are pretty uniform. I am
          pretty sure some big variations will be seen in the bad ones, my failures ran hot,
          but colder is possible. Bruce Roe

          Comment


          • #6
            The panels ought to be under Sunpower's super-duper bumper to bumper warranty they scream to the heavens about. Have you called them ?

            Comment


            • #7
              Originally posted by J.P.M. View Post
              The panels ought to be under Sunpower's super-duper bumper to bumper warranty they scream to the heavens about. Have you called them ?
              Ha ha, that will be fun to learn the results of.
              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

              Comment


              • #8
                Originally posted by Mike90250 View Post

                Ha ha, that will be fun to learn the results of.
                Well, it would be interesting to me, at least, and for several reasons, to see if they are as good as their word hyped up word.

                As for the OP looking for comments/suggestions: Call the vendor or Sunpower after you read their warranty that was in effect in 2008 (which BTW, does not appear to have changed too much).

                Sounds like the OP may possibly not be aware that the installation may well still be under warranty, at least in theory, or that messing with the system may possibly void any warranty.

                Where's the harm in asking ?

                Comment


                • #9
                  Yea, the docs state 12 years for mfg defects and then 20y 90% and 25y 80% (afair) performance guarantee. I suppose a broken panel has peformance of 0 so it would fall into this anyway? And that covers the panels not service and reinstall. I found refurb panels for $80 on eBay so that's not a big issue.

                  But first I need to know what's wrong and that's gonna take me some time.

                  Comment


                  • #10
                    Originally posted by MichKrom View Post
                    Yea, the docs state 12 years for mfg defects and then 20y 90% and 25y 80% (afair) performance guarantee. I suppose a broken panel has peformance of 0 so it would fall into this anyway? And that covers the panels not service and reinstall. I found refurb panels for $80 on eBay so that's not a big issue.

                    But first I need to know what's wrong and that's gonna take me some time.
                    Finding out what's wrong is part of the warranty.

                    Comment


                    • #11
                      Have you had a look at the panels, up close? Any discolored cells?
                      2.2kw Suntech mono, Classic 200, NEW Trace SW4024

                      Comment


                      • #12
                        No discoloration of panels I can see. They are bit dirty but again, uniformly dirty. Will clean them up,

                        I was wrong on warranty, it is 10 years for product (I am out of it) and 12 years for Power no less than 90% and 25 years for no less than 80%. The warranty's language suggest they do not cover replacement cost: "SunPower will replace such loss [in power] by either providing to the Customer additional PV modules to make up such loss in power or by providing monetary compensation equvalent to the cost of additional modules".

                        Comment


                        • #13
                          Could be a combiner breaker tripped...
                          OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

                          Comment


                          • #14
                            [QUOTE=MichKrom;n400835]No discoloration of panels I can see. They are bit dirty but again, uniformly dirty. Will clean them up,




                            The discoloring I'm referring to would be quite obvious.

                            Sunpower brown cells (3).jpgSunpower brown cells 2 (3).jpg

                            2.2kw Suntech mono, Classic 200, NEW Trace SW4024

                            Comment


                            • #15
                              Nothing that strong but there are some that have different tint.

                              Here are the pictures:
                              https://photos.app.goo.gl/BgcbwVtjwuQmejRf6

                              Plot thickens:
                              - at ~2PM 190V/7A and 250/9A - note that panels are rated at 5A so with two strings in parallel it should be possible to get to 9A
                              - at ~4PM both arrays started to produce the same amount of power (according to inverters) still with different voltages but similar amps (190V/250V and both at ~4A and reported power about 1kW)

                              Something is not adding up.

                              I will be doing some more experiments:
                              - covering pannel by pannel and observing the changes
                              - turning the house ooff and using the SmartMeter to measure power sent to the grid
                              Last edited by MichKrom; 07-14-2019, 02:10 AM.

                              Comment

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