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  • #31
    Originally posted by sensij View Post
    There is no direct connection on your inverters between the AC grounded conductor (neutral) and the DC grounded conductor because there is *no* DC grounded conductor. The only AC/DC connections are between the *ungrounded* conductors, L1/L2 on the AC side. Therefore, the DC grounding system is necessary.
    I read 690.47(C) as related to transformer based inverters where there's no connection between DC & AC parts except through magnetic field. Looks like I'm not alone with this interpretation: http://forums.mikeholt.com/showthread.php?t=178911 post #2. I do realize it is all moot point as what matters how my AHJ sees it, even post from MH forum makes reference to AHJ interpretation. Rhetorical question but who on Earth writes NEC in such ambiguous way that ppl with years of experience can have justifiable and opposite opinions?

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    • #32
      That Mike Holt post is saying the same thing I am... Under 2014 NEC, 690.47(c) applies. The only leniency you get accounting for the actual technical requirements of the inverter is that the GEC may be sized as an EGC.
      CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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      • #33
        Originally posted by sensij View Post
        That Mike Holt post is saying the same thing I am... Under 2014 NEC, 690.47(c) applies. The only leniency you get accounting for the actual technical requirements of the inverter is that the GEC may be sized as an EGC.
        In that case I need to buy/rent/borrow crimping tool to irreversibly connect 2 inverters to the common GEC wire running from MSP ground bar or run 2 individual wires from each inverter to MSP ground bar. These GEC wire(s) would pass through subpanel and AC Disconnect box on their way to inverters without actually connecting to the subpanel's or AC Disconnect ground bars.

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        • #34
          No, the ground bars built in to the disconnect and/or subpanel should be listed for this use, and are a valid way to tap the GEC that runs back to the MSP.
          CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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          • #35
            Final update- passed 3rd inspection few days ago without much hassle. Today I got PTO issued by SCE so it's already running at full power and clocked 7.125 kW around 1:30 PM today despite few clouds passing by so I'm pretty happy with the result.

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            • #36
              Originally posted by max2k View Post
              Final update- passed 3rd inspection few days ago without much hassle. Today I got PTO issued by SCE so it's already running at full power and clocked 7.125 kW around 1:30 PM today despite few clouds passing by so I'm pretty happy with the result.
              Nice output. Not too hot and maybe some added irradiance from clouds. 7,125/7640 = .928. Congrads on the PTO.

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              • #37
                Originally posted by J.P.M. View Post

                Nice output. Not too hot and maybe some added irradiance from clouds. 7,125/7640 = .928. Congrads on the PTO.
                Thank you, let's see if it was true or just some SMA data logging spike .
                This board was really helpful in many ways- starting from overall approach all the way to implementation details:

                - I used variation of one of the foobar1 suggestions and hid many conduits inside the wall by opening piece of drywall from inside the garage. Without that it would look a lot messier with 2 inverters.
                - sensij helped a lot with NEC related details
                - SK helped on the grounding issues not on this thread but he left quite a trace on this board
                - even you helped with your healthy dose of brutal common sense

                some pics of not yet patched wall and around
                Attached Files

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                • #38
                  Originally posted by max2k View Post

                  Thank you, let's see if it was true or just some SMA data logging spike .
                  This board was really helpful in many ways- starting from overall approach all the way to implementation details:

                  - I used variation of one of the foobar1 suggestions and hid many conduits inside the wall by opening piece of drywall from inside the garage. Without that it would look a lot messier with 2 inverters.
                  - sensij helped a lot with NEC related details
                  - SK helped on the grounding issues not on this thread but he left quite a trace on this board
                  - even you helped with your healthy dose of brutal common sense

                  some pics of not yet patched wall and around
                  You're welcome. None of us is as smart as all of us. FWIW, Using SAM, and depending on the variables you plug in, the LG's you have actually outperform S.P. 327's STC Watt to STC Watt on an annual basis for many locations/orientations. See how the array does on a clear day. Looking forward to the flix.

                  Add: FWIW only, just recording today's output - pt. cloudy/hazy sun conditions all day, probably not unlike you. I had a cloud spike at 1225 hrs. of 4,867 W, 4,867/5232 = 0.930, vs. your 0.928 spike . Clear day max. instantaneous/STC rating this time of year for me runs around 0.85 - 0.87 depending mostly on precipitable water vapor in the atm.
                  Last edited by J.P.M.; 07-20-2017, 12:21 AM.

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                  • #39
                    Originally posted by J.P.M. View Post

                    You're welcome. None of us is as smart as all of us. FWIW, Using SAM, and depending on the variables you plug in, the LG's you have actually outperform S.P. 327's STC Watt to STC Watt on an annual basis for many locations/orientations. See how the array does on a clear day. Looking forward to the flix.

                    Add: FWIW only, just recording today's output - pt. cloudy/hazy sun conditions all day, probably not unlike you. I had a cloud spike at 1225 hrs. of 4,867 W, 4,867/5232 = 0.930, vs. your 0.928 spike . Clear day max. instantaneous/STC rating this time of year for me runs around 0.85 - 0.87 depending mostly on precipitable water vapor in the atm.
                    Well, I think the performance number I got was wrong- I was trying to set time zone on SMA inverters at a time and that leads to 'spikes' in the data readout. Yesterday it went as high as 75kW (!). After some fight with time zone settings (who wrote that POS?) I finally managed to get my 2 inverters in synch and their combined peak was at 6,168 kW today at 1:45 PM. The total yield for the day was 48kWh, the only number I'm after . My STC rating is 24x305 = 7320W so the same ratio would be 6168 / 7320 = .84 I found POCO doesn't log my numbers correctly- there's no negative values on their daily consumption graphs, it just goes to some close to 0 values in 20- 40 watts range. Well, I have pic of their meter showing 4+ kW going back to grid so if they don't get this correctly today I'll give them a call on Monday. The graph (1kW/div vertical): 2017_07_21.png
                    Last edited by max2k; Today, 12:21 AM.

                    Comment


                    • #40
                      Originally posted by max2k View Post

                      Well, I think the performance number I got was wrong- I was trying to set time zone on SMA inverters at a time and that leads to 'spikes' in the data readout. Yesterday it went as high as 75kW (!). After some fight with time zone settings (who wrote that POS?) I finally managed to get my 2 inverters in synch and their combined peak was at 6,168 kW today at 1:45 PM. The total yield for the day was 48kWh, the only number I'm after . My STC rating is 24x305 = 7320W so the same ratio would be 6168 / 7320 = .84 I found POCO doesn't log my numbers correctly- there's no negative values on their daily consumption graphs, it just goes to some close to 0 values in 20- 40 watts range. Well, I have pic of their meter showing 4+ kW going back to grid so if they don't get this correctly today I'll give them a call on Monday. The graph (1kW/div vertical): 2017_07_21.png
                      That 0.84 sounds about right.

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