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  • Question about SolarEdge inverter sizing and clipping

    The SolarEdge inverter line advertises that the traditional inverter allows DC oversizing of 135% and the HD Wave 155%. I believe but am not certain that this is a warranty thing and that the inverter would clip at rated watts. Their data sheet shows Max AC output at 8350 for the SE7600A and 7600 Max AC output for the SE7600H-US.

    Am I correct that these inverters clip when they reach max AC output? So if I have an array of 8450DC in San Diego I won't get full annual output with the HDWave, correct?

    Thanks.

  • #2
    Originally posted by so_cal_burbs View Post

    Am I correct that these inverters clip when they reach max AC output? So if I have an array of 8450DC in San Diego I won't get full annual output with the HDWave, correct?

    Thanks.
    Both Solaredge 7600 W inverters clip at 7600 W. An 8.4 kW array will probably clip a little bit in spring, but the value of the energy lost will be insignificant.
    CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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    • #3
      Originally posted by so_cal_burbs View Post
      So if I have an array of 8450DC in San Diego I won't get full annual output with the HDWave, correct?

      Thanks.
      Your installer chose the right size inverter for the job. You have a 1.1 DC oversize ratio. Which is the same oversize ratio as mine, also in San Diego with the HDWave. Over a year, optimistically, you may lose 10-50kwh worth of production or about $10 worth of electricity due to clipping - although that is doubtful. Personally, if I had to do it all over again, I wouldn't mind going 1.25 ratio in San Diego.

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      • #4
        Originally posted by sensij View Post

        Both Solaredge 7600 W inverters clip at 7600 W. An 8.4 kW array will probably clip a little bit in spring, but the value of the energy lost will be insignificant.
        I'm not sure about this. I have the SE 7600 inverter and the other day it showed 7849 W at 10:20 AM:

        https://pvoutput.org/intraday.jsp?id...59&dt=20171031
        https://pvoutput.org/list.jsp?userid=59404

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        • #5
          Originally posted by macaddict View Post

          I'm not sure about this. I have the SE 7600 inverter and the other day it showed 7849 W at 10:20 AM:

          https://pvoutput.org/intraday.jsp?id...59&dt=20171031
          Is that based on what the inverter is telling you, or a revenue grade meter?
          CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

          Comment


          • #6
            Originally posted by sensij View Post

            Is that based on what the inverter is telling you, or a revenue grade meter?
            Inverter reporting. I have the SE 7600A inverter.
            https://pvoutput.org/list.jsp?userid=59404

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            • #7
              Originally posted by macaddict View Post

              Inverter reporting. I have the SE 7600A inverter.
              I have one of those, and an SE3000A on a different system. I'm skeptical that the inverter is really producing more than 7600 W, because even though the data sheet indicates that a 3000 W inverter has peak output of 3300 W, and the inverter itself has occasionally reported output a couple percent over the 3kW rating, those values were never confirmed by the revenue grade meter I put in to independently monitor the output. For example, the peak power the RGM measured on 3/22/16 was 2940 W, against the 3072 W reported by the inverter for that period. (The RGM CT's were located right at the inverter, so AC loss doesn't explain the difference).

              When you see the DC voltage spike up from its baseline, that indicates that clipping is occurring. If the power output associated with the clipping events is not a stable number, it casts doubt on the consistency of the measurement and data processing the inverter performs to determine its "power generated" metric. Even if the power output it is reporting were accurate, the DC voltage charts are suggesting that something around 7900 W is the clipping limit of your inverter, not the 8350 W that the OP is getting from the inverter's data sheet.

              The inverters only need to have accuracy of 5% to meet CA standards, and SolarEdge, in particular, seems to consciously use that range.
              Last edited by sensij; 11-06-2017, 06:10 PM.
              CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

              Comment


              • #8
                New here. Our system powered up officially on Jan 16.
                - 18 panels, LG365Q1C-A5
                - 18 SolarEdge P400 Optimizers
                - SolarEdge SE500H-V5 Wave
                - DC Rating 6.57 KW DC

                The system is rated 6.57 KW but it is clipping at 5000 watts. Even in the winter with the sun low it is clipping for long periods. We live in Redding, CA, the 2nd sunniest city in the U.S. after Yuma AZ. When summer comes we have blue skies with zero clouds for months at a time. When the sun is in summer position our system will be clipping for hours.

                I don't understand the logic behind the decision to put a 5,000 watt inverter on a 6.57 Kw system. Can anyone shed some light on this? I have a call into the installer to see what they say about this situation.

                I would post a graph of the clipping but I don't see a way to add a photo here.

                Thanks,
                John

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                • #9
                  The good news is that your system will have more clipping in the winter with cold weather. The heat of summer will reduce production.

                  how many hours is the system clipping now?
                  OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

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                  • #10
                    Originally posted by ButchDeal View Post
                    The good news is that your system will have more clipping in the winter with cold weather. The heat of summer will reduce production.

                    how many hours is the system clipping now?
                    It's only happened a few times so far. Just 18 days of operation so far since the system was switched on. Only four hours of clipping total since the system started. We've had clouds and rain. But today was the most as it was the sunniest. Just some high thin clouds. The system clipped from 11:15 am to 12:45 pm continuously. The graph shows a flat line between those times. It looks sort of like a bell curve that's been clipped at 5,000 watts. My "guess" is if it wasn't clipped it might have risen to 5,500 watts. Ambient temperature was 78 degrees F around that time.

                    Question: When I'm trying to determine the loss due to summertime high temperatures is that simply ambient temperature? I wouldn't know how to estimate the surface temperature of an almost black panel.

                    We have many days over 100 degrees F here, sometimes weeks when daytime temperatures are 102 - 112. The sun is intense and there are zero clouds.

                    Is there any reason to believe that an inverter that is sized the way ours is is somehow more efficient than if I had a higher rated inverter installed? Clipping seems detrimental to me unless there is some sort of efficiency factor that I'm not aware of.

                    Comment


                    • #11
                      By those numbers then say you clip equivelant of 2kwh (500w / 4hr) / every 18 days. 365/18, 20.27 days, * 2 = 40kwh a year lost. Peanuts, really. However given the sun is so low this time of year, I guess you will get quite alot more clipping come spring when you still have the cool temps but longer exposure.

                      Your AC/DC ratio is quite high, curious what azimuth and tilt do you have on the panels? Did they undersize the inverter knowing the panels arent facing true solar south or at enough tilt to get maximum exposure?
                      Last edited by ImInPhxAZ; 02-03-2018, 04:13 PM. Reason: typos are the death.

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                      • #12
                        Originally posted by jdonalds View Post

                        Is there any reason to believe that an inverter that is sized the way ours is is somehow more efficient than if I had a higher rated inverter installed? Clipping seems detrimental to me unless there is some sort of efficiency factor that I'm not aware of.
                        With solaredge, no same efficiency for the SE5000H as the SE6000H

                        really little reason to do that unless you have a limit on the input side but I would highly doubt you have a service panel that could handle the 5kw but not the 6kw Just pretty much lazy installers that are not familiar with solaredge
                        Last edited by ButchDeal; 02-07-2018, 05:14 PM.
                        OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

                        Comment


                        • #13
                          Originally posted by ButchDeal View Post
                          With solaredge, no same efficiency for the SE5000h as the SE6000H

                          really little reason to do to do that unless you have a limit on the input side but I would highly doubt you have a service panel that could handle the 5kw but not the 6kw Just pretty much lazy installers that are not familiar with solaredge.

                          I'm seeing a little bit of loss every day now. We are in a near 100% sun period for a few weeks with highs in the 70s (it's 77 F at noon now). Every day the power graph is like a bell curve, clipped at 5,000 watts for about 2 hours a day. I figure I'm losing about 1kWh per day right now due to clipping. The inverter has now clipped 5 out of the last 8 days and will again today.
                          On the other hand I can see a potential answer in the numbers. The LG365Q1C-A5 panel datasheet says it has a Maximum Power (Pmax) of 365 watts, but the NOCT Maximum Power is shown as 275 watts. We have 18 panels x 275 watts equals 4950 watts for the whole system. From that I could see how the installers could have chosen a 5000 watt limited inverter. I still don't see the harm in bumping up to the next inverter. Someone said the cost differential isn't much. The panels are obviously capable of outputting over 5000 watts.

                          I don't know what the roof angle is or the orientation to the south is. Our house isn't exactly facing south but it's not far off.

                          Comment


                          • #14
                            Originally posted by jdonalds View Post
                            Question: When I'm trying to determine the loss due to summertime high temperatures is that simply ambient temperature? I wouldn't know how to estimate the surface temperature of an almost black panel.

                            We have many days over 100 degrees F here, sometimes weeks when daytime temperatures are 102 - 112. The sun is intense and there are zero clouds.

                            Is there any reason to believe that an inverter that is sized the way ours is is somehow more efficient than if I had a higher rated inverter installed? Clipping seems detrimental to me unless there is some sort of efficiency factor that I'm not aware of.
                            On the panel temps., they will run hotter than the air temp.

                            Some considerations:

                            1.)The panels' surface temp. will be higher than the surrounding air.

                            2.) A dark roof will have surrounding air temps. of maybe 2-4 deg. F warmer than the ground air temp. in summer mid day with a lot of wind, to maybe 6 - 12 F warmer than the ground air on still days.

                            3.) A VERY ROUGH number for panel cell temp. in deg. C.is : (((POA irradiance)/(32)) + 3) + array area ambient air temp. in deg. C., with POA in W/m^2. The 32 is the very approximate (with some variation depending mostly on wind) heat loss (or gain) coefficient from/to the panel in W/(m^2 deg. C.).

                            4.) I've measured/calced. that heat loss coefff. for my array several hundred times. The number I got (~ 32 W/m^2 deg. C.) seems to agree fairly well with what a calc of the NOCT temp. usually or commonly works out to be, that is, with a NOCT of, say, 47 C. open circuit NOCT at 25 C. ambient temp. and 1m/sec. wind velocity works out to something like 800 W/m^2/(47-25 + 3) C. = 32 W/(m^2 deg.. C.), with the 3 deg. an approximation of the difference between the array/panel surface temp. and the cell temp. for full sun.

                            5.) I've also found that acceptable cell temp. approx. can be found from knowing the panel/array STC voltage and the actual, measured voltage and knowing the voltage drop per deg. C from the panel spec sheet. Those results compare favorably enough to measurements to be used as a pretty good check on actual measured temps. Details on request.

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                            • #15
                              My installer has requested SolarEdge take a look at my system. I believe we lost at least 2KWh just today alone. Cool weather and lots of sun created a bell curve with a three hour long flat top today.

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