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  • Energy Production Cap

    Hi All, We installed a 25 panel LG unit with an Enphase invertor last November. Lately we've noticed that the energy production flatlines several time a day at 1535 wh during early afternoon peak hours. My understanding was these panels can produce 300-400wh each. Am I missing something here or am I doing the math wrong.

  • #2
    Originally posted by Mokodo View Post
    Hi All, We installed a 25 panel LG unit with an Enphase invertor last November. Lately we've noticed that the energy production flatlines several time a day at 1535 wh during early afternoon peak hours. My understanding was these panels can produce 300-400wh each. Am I missing something here or am I doing the math wrong.
    Clarify in Watts where you are seeing the flatline? Your number of "1500 wh" may be an energy measurement (Watthours) not a power measurement. Also 300 Watts times 25 panels might see 6000 to 7000 Watts depending on location, orientation and tilt. Do you know the model number of Enphase microinverters and the STC rating of the panels?
    Last edited by Ampster; 03-28-2020, 11:58 AM.

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    • #3
      This month, in periods of no clouds, my SolarEdge SE3800 inverter has been clipping the production from my 12 LG335 panels at 3.879kW (AC). Looking at the system settings the inverter has the power limit set at 100% so it is working as designed.

      Is your inverter clipping the output of those panels?

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      • #4
        Originally posted by Ampster View Post

        Clarify in Watts where you are seeing the flatline? Your number of "1500 wh" may be an energy measurement (Watthours) not a power measurement. Also 300 Watts times 25 panels might see 6000 to 7000 Watts depending on location, orientation and orientation. Do you know the model number of Enphase microinverters and the STC rating of the panels?
        The panels are LG335N1C-V5 and the inverter is an Enphase IQ Combiner 3 (X-IQ AM1-240-3)

        I'm getting this data from their enlighten reports. As you can see, the flatline starts at 1pm to 4pm maxed at 1535wh.

        Capture1.JPG
        Last edited by Mokodo; 03-26-2020, 10:56 PM.

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        • #5
          Originally posted by RichardCullip View Post
          This month, in periods of no clouds, my SolarEdge SE3800 inverter has been clipping the production from my 12 LG335 panels at 3.879kW (AC). Looking at the system settings the inverter has the power limit set at 100% so it is working as designed.

          Is your inverter clipping the output of those panels?
          I wouldn't know where to check. Excuse my ignorance on this... Please instruct on how this can be achieved. Thanks much.

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          • #6
            Originally posted by Mokodo View Post

            I wouldn't know where to check. Excuse my ignorance on this... Please instruct on how this can be achieved. Thanks much.
            Sorry, I can't help you with the details of your Enphase equipment as I am only familiar with the SoalrEdge equipment I have installed.

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            • #7
              Originally posted by Mokodo View Post

              The panels are LG335N1C-V5 and the inverter is an Enphase IQ Combiner 3 (X-IQ AM1-240-3)

              I'm getting this data from their enlighten reports. As you can see, the flatline starts at 1pm to 4pm maxed at 1535wh.

              Capture1.JPG
              That model number is your Envoy that is gathering the information from your 25 microinverters and doing the aggregate reporting. Look for some listing of inverters that probably start with "IQ..." . There should be 25 of those. The full model number can be looked up to see what that model clips at. My guess is that they clip at 300 Watts each.

              That screen shot was helpful. Your inverters are clipping, starting at 1PM as you pointed out. However the cursor was at 12:00 and the reading was for a fifteen minute period at 12:00 and if you multiply it by 4 the result would be 6140 kWhr for an hour which means they were putting out 73% of the panels max STC capacity of 8,375. If you slide the cursor over the flat part you might see a value 20% greater which might mean you could be getting almost 90% of STC capacity which is not bad for this time of year. The amount lost at the top is not that much but your system was probably designed with a DC to AC ratio above 1 to 1 which is quite common. A solar panel rarely puts out its full STC rating so you should not expect to ever see 8300 Watts even on the best of days.

              If it is any comfort I have the same inverter as @RichardCullip noted above but I have 5700 Watts of panels and clip at 3879 or 66% of capacity, I do get more energy than if my panels had been matched to my inverter. However If I had been given the choice to spend a few hundred dollars on a larger capacity inverter I would have taken that option.

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              • #8
                Originally posted by Mokodo View Post

                The panels are LG335N1C-V5 and the inverter is an Enphase IQ Combiner 3 (X-IQ AM1-240-3)

                I'm getting this data from their enlighten reports. As you can see, the flatline starts at 1pm to 4pm maxed at 1535wh.

                Capture1.JPG
                Under absolutely ideal conditions and a clear sky, your 335 W panels will produce 335 W or so per panel, but not very often. That's the reality of it.

                Under common and decent conditions, expect your panels to produce ~ 85% or so, +/- a bit of that 335 W or ~ 285 W (or 24 panels * 285 W/panel = ~ 6.8 kW or so under clear sky, more in cool weather, less in hot weather and less in winter because the sun angle on the array will be less favorable (and so less solar fuel will be available).

                Among pother things, you need to learn the difference between a watt-hour, a unit of energy, and a watt, a unit of power and also how what you bought works.

                Snoop around on the net and find a free download of "Solar Power Your Home for Dummies". You need a general education about residential PV. Also, download and run something called "PVWatts". It's software for residential PV modeling for non tecnical folaks and a steep learning curve. Read the help/info screens a few times before you start, but after you read the book and then make a few runs. All, that will also help with your self education. After a read of the book and a some experience w/ PVWatts, come back w/questions you can't answer on your own. Do that and the answers you get back here will have a lot more meat on them. You'll also be considerate of folks here who want to help you.

                The graph you included is showing units of energy (watt-hours) your system is producing every 15 minutes. If your inverter is clipping at 1,535 watt-hours (Wh) over 15 minutes, it's putting out (1,535 watt-hours) X 4 ea. 15 minute periods/hour = 6,140 watts (W) or 6.14 kilowatts (kW).

                If you want some intelligent conversation about all this, please provide your location (zip code), array size (in STC W), array orientation (tilt and azimuth), and any shading on the array. Those parameters are some of the basics necessary for folks here to have a better chance at understanding what your array is doing. Your self instruction will also help.

                Basically, as a first SWAG, if all's running right it looks like you have a 6kW inverter and a system that's oriented west of south with not a lot of shade, at least at this time of year.

                Clipping is not unusual this time of year as the sun gets to a more favorable location and the weather is usually a lot cooler (at least in the northern hemisphere) than in the summer, making for more efficient panel operation and with it a higher likelihood of clipping. Clipping will probably occur a lot less as the weather gets warmer.

                Welcome to the neighborhood and the forum of fewer illusions but often more straight information.

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                • #9
                  Could it be that this system uses multiple Enphase microinverters, one per panel, under each panel, and the outputs of the microinverters are combined in the combiner? You can't easily visibly see the microinverters because they're up on the roof, nestled under the panels.

                  If your app allows you to see the output of each individual panel, then that's very likely what you have. They signify it as the output of each panel, but are really showing you the output of each microinverter. Inside each microinverter is a small power measurement system that is reporting back to you.

                  One Enphase iQ7 microinverter will put out 250 watts maximum. If you have 24 of them, that's 6000 watts maximum out of the whole system, limited by the microinverters. If you are getting 1535 wh every 15 minutes, that's 6140 watts continuous, or 6000 watts within 2.5% error.

                  If you do have iQ7 microinverters, then the above graph shows the system working perfectly.

                  The reason why they limit power is to prevent damage to the microinverter from too much heat or too much current. Those microinverters are small, compact, efficient but not perfect boxes. Each unit is roughly 96% efficient, so when delivering 250 watts, it has to dissipate 10 watts. That's a significant amount of heat. If they let it operate at higher output power, that would mean even more heat.

                  It's complicated to explain how the microinverter limits power, but it doesn't burn the excess as heat. It limits power by adjusting the power point tracking algorithm to operate slightly off maximum. In other words, by changing the current drawn from the panel, they operate the panel in a less optimal configuration, reducing its actual output power.

                  It is common to size a system such that the microinverter limits total output power. As you see, you are only limited at the peak of the daily production. If you bought larger, more expensive microinverters, you would get a tiny amount more power at the peak of the day, but the total additional energy (power x time) may not be enough to justify the extra cost.

                  Also, after 10 years, your 335 watt panels will degrade roughly 5% and perhaps not reach limiting. So paying extra for bigger microinverters now may be wasted money later.

                  Or it could be that your installer was just cheap and didn't spend the extra $20 per microinverter to upsize them for higher output.
                  7kW Roof PV, APsystems QS1 micros, Nissan Leaf EV

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                  • #10
                    Originally posted by bob-n View Post
                    .........

                    One Enphase iQ7 microinverter will put out 250 watts maximum. If you have 24 of them, that's 6000 watts maximum out of the whole system, limited by the microinverters. If you are getting 1535 wh every 15 minutes, that's 6140 watts continuous, or 6000 watts within 2.5% error.
                    The only thing I would add is that the IQ7 microinverters come in various models, some of which have maximums above 250 Watts. I do agree that the system appears to be operating as designed. It would be nice to get more facts to confirm that assumption.

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                    • #11
                      Awesome info from everyone. Thank you all for taking the time. I don't have additional technical info at this time until I make way to the roof. The invoice was pretty vague and didn't include any specs. I'm curious to see pricing on the inverter upgrade and if additional power can justify the cost. I'll reach out to the supplier and see if I can obtain technical specs.

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                      • #12
                        I haven't personally used the Enphase app, but it is supposed to have "everything" in it. One of their screens is supposed to have a menu called Devices. I think that will tell you what you have installed, but can't confirm that.
                        The IQ7 microniverter is a 250 watt model and is appropriate for 60 cell panels.
                        The IQ7+ microinverter is a 295 watt model and is appropriate for 60 cell and 72 cell panels.
                        The IQ7X microinverter is a 320 watt model but is only appropriate for high cell count panels (ex: 96 cell.)
                        The IQ7A microinverter is a 366 watt model and is appropriate for 60 cell and 72 cell panels.
                        The model is probably encoded into the serial number, so if you can read the microinverter serial number from the app, you can find out the model.
                        You can learn a lot more by going to the Enphase website or using google to search for Enphase iq7.
                        If you can stare at a panel from the ground and have a bit of patience, you can count the number of cells. A 60 cell panel will have a grid of 6x10 cells and be shorter than a 72 cell panel. A 72 cell panel will be 6x12 cells.
                        7kW Roof PV, APsystems QS1 micros, Nissan Leaf EV

                        Comment


                        • #13
                          Originally posted by Mokodo View Post
                          Awesome info from everyone. Thank you all for taking the time. I don't have additional technical info at this time until I make way to the roof. The invoice was pretty vague and didn't include any specs. I'm curious to see pricing on the inverter upgrade and if additional power can justify the cost. I'll reach out to the supplier and see if I can obtain technical specs.
                          FWIW, once you get familiar w/PVWatts, there's a pretty simple way to guesstimate how much energy you might be losing by undersized inverter(s) that's probably good to +/- 10 % or so.

                          Comment


                          • #14
                            Originally posted by bob-n View Post
                            I haven't personally used the Enphase app, but it is supposed to have "everything" in it. One of their screens is supposed to have a menu called Devices. I think that will tell you what you have installed, but can't confirm that.
                            The IQ7 microniverter is a 250 watt model and is appropriate for 60 cell panels.
                            The IQ7+ microinverter is a 295 watt model and is appropriate for 60 cell and 72 cell panels.
                            The IQ7X microinverter is a 320 watt model but is only appropriate for high cell count panels (ex: 96 cell.)
                            The IQ7A microinverter is a 366 watt model and is appropriate for 60 cell and 72 cell panels.
                            The model is probably encoded into the serial number, so if you can read the microinverter serial number from the app, you can find out the model.
                            You can learn a lot more by going to the Enphase website or using google to search for Enphase iq7.
                            If you can stare at a panel from the ground and have a bit of patience, you can count the number of cells. A 60 cell panel will have a grid of 6x10 cells and be shorter than a 72 cell panel. A 72 cell panel will be 6x12 cells.
                            Took a look and realized they have a new look and the devices are listed as IQ7-60-2-US. I believe these are the 250 Watts.

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                            • #15
                              Did you ever figure out what the kW output of your system was when it was clipping? Some Enphase screens let you toggle between power (kW) and energy (kWh). My guess was it was about 7500 or 300 Watts per microinverter.

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