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12 KW Ground Mount In Poway CA. Daily Install Progress

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  • #16
    Another Ground-Mount Fan

    I am glad I stumbled on this thread from Poway, and I noticed the similarity to lkstaack's ground array. Both of you attached some great photos of your install progress. My proposed 7.32KW array is also on a slope ( 27 degrees ), however it is reversed ( north slope of Puente Hills ). I know this sounds absurd, but the hillside was terraced in 1929 for an avocado grove, so rather than being a continuous hillside, it consists of 8 flat terraces and 9 (roughly) 45 degree slopes. The trees are long gone, and the slopes have become more rounded, but the terrace I have chosen for my array-site still has a good 15' of level space between slopes. The comparison of the excavating methods used by Poway & lkstaack are particularly of interest to me, as I have been likewise studying both approaches ( hand-dig, machine-trenching, auger-boring ). Unlike the soil conditions in Poway ( granite, decomposed granite ), the soil at my chosen elevation ( 879' AMSL) is designated as Upper Fernando conglomerate; river-washed sandstone & limestone, evenly graded from silt up to 15" boulders ( with an occasional two-footer ).
    Using IronRidge's design-assistant, I concluded that my ideal foundation dimension should be 16" diameter x 42" deep. With the larger diameter I should be able to use a two-man gas auger to dig out most of the 8 holes required for the IronRidge pipe foundation. If I encounter a large boulder, I have a 1-1/4" x 6' wrecking bar that should be able to handle it. I am planning on using 16" x 4' Sonotubes to form up the concrete, so I will be able to compensate for any "super holes" that are caused by large rocks. I once contemplated renting a Ditch-Witch trencher to dig out the 95' run from the array to my back walkway, but opted instead for a hand-dig, since I am the "contractor" for the job, am unwilling to run the risk of a "downhill runaway trencher" accident.
    I finished surveying the site & setting grade-stakes today, & estimate that I will have to move between 1-1/2 to 2 yards of earth from the back of the terrace to level-out the site.

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    • #17
      Originally posted by Poway View Post
      I followed your install on this forum... thanks for sharing... gave me things to ask up front for my install...

      My array is in a 10 deg slope area (your's much greater) and the path to my array is mostly <20 deg.

      Which means I was able to use a trencher. there is a big difference between jack hammers and trenchers.

      The trencher "should" travel the whole 200 ft in less than 1 hour... but the reality is that it took almost 1 hour to cut thru the largest bolder (about 15 inch deep cut 10 feet long ... the trench is 20+ inches ... rock below surface)

      Plus mine is all granite and decomposed granite. I know granite... See examples below

      The picture labeled stay away from is hard granite... trencher would do nothing to it...
      The large rock above ground is one that a trencher will cut easily
      The picture underground is a cut thru a rocks that I did not even notice were there (notice the little pile of granite chunks)

      Had to resize photos
      I had no idea that a trencher could cut through stone. The contractor initially tried using an auger for the post holes for my array, but it was hard to establish a bite into the ground due to the cobble, and when you did, the cobble had a tendency to freeze the the bit and send the operators flying.
      LG280/SE6000/[url]http://tinyurl.com/pav2bn8[/url]

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      • #18
        Originally posted by lkstaack View Post
        . The contractor initially tried using an auger for the post holes for my array, but it was hard to establish a bite into the ground due to the cobble, and when you did, the cobble had a tendency to freeze the the bit and send the operators flying.
        No way a hand held auger would make an adequate hole for a ground mount of any size - maybe for one or two panels.
        [SIGPIC][/SIGPIC]

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        • #19
          Originally posted by russ View Post
          No way a hand held auger would make an adequate hole for a ground
          mount of any size - maybe for one or two panels.
          Just watched a 24" auger in action here for a metal out building. It was mounted on a several ton
          machine and hydraulically powered, quite powerful. Bruce Roe

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          • #20
            Originally posted by bcroe View Post
            Just watched a 24" auger in action here for a metal out building. It was mounted on a several ton
            machine and hydraulically powered, quite powerful. Bruce Roe
            Yep and bigger yet for drilling for piling. But a hand held one for a 12 kW ground mount? Handheld ones are toys.
            [SIGPIC][/SIGPIC]

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            • #21
              Originally posted by russ View Post
              No way a hand held auger would make an adequate hole for a ground mount of any size - maybe for one or two panels.

              I'm not exactly sure what type of ground mount you are referring to.

              High price adjustable angle mounts (that I see more in northern latitudes... Maine, Washington State etc.) that have a single central post and thus require a significant hole.

              In san diego most ground mounts (including mine) are cheap multi-pole designs.

              For example: Ikstaack's 21 panel used Type of footing: Concrete, 12" diameter, 42" deep using sonitubes x 10 footings
              The weight of each footing is 412 lbs (2.75 cubic feet x 150 lbs per cubic foot)
              The total weight of all footings is 4123 lbs OR 196 lbs per panel

              My array: 40 panel uses Concrete, 12" diameter, 56" high using sonitubes x 18 footings
              The weight of each footing is 549 lbs (3.665 cubic feet x 150 lbs per cubic foot)
              The total weight of all footings is approx. 10,000 lbs OR 250 lbs per panel
              Because all the footings are tied together with 1.5" steel tubing the array should be very stable in cross winds...


              The 12" diameter holes for my array were cut with a hand held auger (2 person)
              A nice new one as can be seen in the photo Day2_Wait_for_inspector2s.jpg

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              • #22
                Originally posted by Poway View Post
                Plus mine is all granite and decomposed granite. I know granite... See examples below

                [ATTACH=CONFIG]6601[/ATTACH][ATTACH=CONFIG]6602[/ATTACH][ATTACH=CONFIG]6603[/ATTACH]

                The picture labeled stay away from is hard granite... trencher would do nothing to it...
                The large rock above ground is one that a trencher will cut easily
                The picture underground is a cut thru a rocks that I did not even notice were there (notice the little pile of granite chunks)
                What installation are you talking about when you said, "The 12" diameter holes for my array were cut with a hand held auger (2 person) ?
                [SIGPIC][/SIGPIC]

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                • #23
                  Originally posted by russ View Post
                  What installation are you talking about when you said, "The 12" diameter holes for my array were cut with a hand held auger (2 person) ?
                  I believe Poway meant his ground array. His pictures show an auger and what looks like a jack hammer.

                  I guess depending on how deep the hole needs to be and the type of soil you can use a 12" hand auger. They may not be nice and round but there will be some type of hole made.

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                  • #24
                    Originally posted by Poway View Post
                    Placeholder for Day 3

                    Total Man Days On-site (doesn't include the time to get all material together and bring to site)

                    Digging Holes (Mon): 1 man day (2 people 1/2 day)
                    Pouring Concrete (Tues): 1 man day (2 people 1/2 day)
                    Assembling Array (Wed): 2.5 man day (2 people all day, one extra person helping with panels 1/2 day)
                    Inverter/Cleanup (Thurs): 1 man day (2 people 1/2 day) <== THIS IS GUESS

                    Total 5.5 Man Days.... for a 40 panel system
                    For my 45 panel system I paid $400 for a bobcat and 2 operators that took about 1 hour to drill the holes, so I'm not counting that. It took me with a helper about 10 man-days (2 men for 3 weekends) to build the Unirac U-LA frame after the holes were drilled and almost 1.5 man-days (3 men half day, concrete truck there for 3 hours) to pour 5 yds. concrete from a truck with a concrete buggy. I completely built and leveled the frame before pouring concrete. Then several weekends (at least 6 man-days) for me to wire the inverters and install the panels. Add another day for sub-panel & feed Elect panels.jpgSolar2.jpgconnections. I'm dying to see what a 5.5 man-day ground installation looks like!
                    Jeff, BSEE, 22.3KW, 45-240W w/M190, 46-260W w/M250

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                    • #25
                      Originally posted by JFinch57 View Post
                      It took me with a helper about 10 man-days. I'm dying to see what a 5.5 man-day ground installation looks like!

                      10 man-days - 4.5 cases of beer = 5.5 man-days.
                      24xLG300N+SE7600 [url]http://tiny.cc/n7ucvx[/url]

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                      • #26
                        Originally posted by ericf1 View Post
                        10 man-days - 4.5 cases of beer = 5.5 man-days.
                        ericf1, where is the "like" button!!! To put my project in total perspective the holes were drilled on Dec 26, we poured the cement on Martin Luther King day and it snowed like heck that night. Everything was frozen & too cold to work for the next 6-8 weeks. Started back up in April and got my final inspection on June 30. Basically was a 4 month project spread over 6 months, but 1 month included some unrelated fence work, so 3 months of weather permitting weekend work.
                        Jeff, BSEE, 22.3KW, 45-240W w/M190, 46-260W w/M250

                        Comment


                        • #27
                          Originally posted by russ View Post
                          What installation are you talking about when you said, "The 12" diameter holes for my array were cut with a hand held auger (2 person) ?

                          The auger used to drill my 12" diameter holes is similar to the two person unit shown in this photo

                          auger.jpg

                          Sorry I may have caused confusion if by hand auger you met a hand powered auger. Truely Old School

                          Hand__Auger.jpg

                          I thought you met difference between a gas powered auger held by one or more people and a gas powered auger that is mounted to a larger piece of equipment

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                          • #28
                            [QUOTE=J... It took me with a helper about 10 man-days (2 men for 3 weekends) to build the Unirac U-LA frame after the holes were drilled and almost 1.5 man-days (3 men half day, concrete truck there for 3 hours) to pour 5 yds. concrete from a truck with a concrete buggy...[/QUOTE]

                            It would have taken me much much much longer... researching all the right equipment double checking measurements...

                            But the laborers in my case were very experienced... Main guy had installed over 1000 arrays in 15 years (approx 1/2 ground mount).
                            To look at them, they didn't move fast or seem rushed, but they had no wasted movement.

                            When I do a job I am not familiar with... I am all about wasted movement.

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