Setting piers

Discussion in 'Alternative Energy' started by MontanaCowboy, Sep 8, 2017.

  1. MontanaCowboy

    MontanaCowboy New Member

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    Hello, new guy here and I'm thankful to have found your forum.
    I own an off-grid ranch secluded deep on a Montana mountain. We've been living on generators and battery banks/inverters (that charge from the generators) and I'm in the process now of installing a complete solar power system. Since I'll never be able to eliminate generators completely (for farm equipment/welders/etc.) I bought a system just to meet the needs of my house to at least eliminate running generators at night (after awhile you can hear them running even after you turn them off!).

    I ended up purchasing the 4.43kw "Homesteader" package from Wholesale Solar (https://www.wholesalesolar.com/1891...-kw-15-panel-solarworld-off-grid-solar-system). After much comparison, I came to believe that this is a well engineered system but I'm certainly no expert which brings me here to this forum in search of assistance. The salesman Jeremy Allen is clearly knowledgeable and courteous and is willing to assist with specific questions. The trouble is, I don't possess the skill set yet to know what questions to ask. I own a commercial refrigeration and welding company, and I've worked as a Journeyman electrician and certified welder (both pipe and structural), but the specifics of solar power are new to me. My only complaint with the system from Wholesale Solar (at this point, at least) is that the accompanying instructions absolutely suck! There is no step by step detailed instructions on how to install their system and they instead refer you to the manufacturer websites of the individual components in most cases and I find this unacceptable.



    [​IMG]
    This is my log cabin home. The red square in on the hillside is where I plan to install my solar panels (the small solar panels in the picture no longer work). The hillside faces almost perfect true south and around a 45 degree incline (being near the 46th parallel, I need a 46 degree slant as I understand it). I want to begin sinking my piers, but I'm having difficulty determining spacing and true square. The Wholesale Solar website refers me to the Iron Ridge website, and the Iron Ridge website appears to assume previous working knowledge of installing solar panels.

    Perhaps I'm just overwhelmed with pieces, parts and stacks of papers and cannot see the answers that should be directly in my face. Any advice on setting my piers would be much appreciated. The CAD drawings assume level ground so the front to rear spacing would be different than when mounted into a hillside if measured laterally across the ground. I suppose I could extend the first level of piers upward and measure level across the top, but am hoping there is a commonly known geometric formula to simplify my measurements. Any other advice and recommendations appreciated.
     
  2. Murby

    Murby Well-Known Member

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    Maybe I can help..
    I hope you did "the math".. so many people think that a 4kw system will actually generate 4kw.. it never happens. If you haven't already done so, you should have checked out the PV Watts calculator from NREL labs. The power calculator is surprisingly accurate and has so far predicted my output to within 2%...

    Unfortunately, you went to one of the most expensive places on the internet to get your stuff. My system is 7.56 kW and I paid $8800 for it and I also have SolarWorld panels..
    One thing that stands out right away is that they sold you the Ironridge XR100 rails instead of the XR1000 rails... Being in such a windy place, they should have kicked up your wind loading to 130mph just to be on the safe side...

    This is intentional.. the fewer things they tell you about installation, the less liability on their part.. But relax, its pretty easy to do.. technically easy.. but labor intensive.
    I just put one in myself using the Solar World panels and IronRidge mounting and I'm also on a slope that has a 36 inch drop over 40 feet.. The big difference is that my slope is east to west, your slope is southern right? That works to your advantage and will save you money on the piping...


    Go to PV Watts and play with the angle of the array to see what works best.. you'll plug in your location and you should be able to see what the exact angle should be.
    Its important you get the exact angle.. being off will cost you about 1% output per degree of error...

    You are overwhelmed by all the little parts... I was too..

    One thing I just noticed when I went to your link showing the package is that they include the ironridge rails but none of the other hardware that's required.. Ironridge is a mounting system.. not just a single part. You should have gotten the IronRidge Ground Mount package that includes the XR rails AND the IronRidge cast aluminum top caps as well as the U-bolts and aluminum angle iron brackets to secure the XR rails. Its as if they sold you half a package or something and want to nickle and dime you to death afterwards...

    I went to Renvu.com and for $8800, I got 28 SolarWorld SW270 panels, an SMA SunnyBoy inverter, and a complete IronRidge Ground Mount system with all the hardware.. all I had to do was buy the 3 inch galvanized piping and concrete..

    If you tell me how you want to organize your panels, and what structure you'll be mounting them on, I can suggest spacing for you and I'll know more about what you need.
    How your panels are organized is most important.. are you putting them in portrait configuration or landscape (up or sideways)? How many rows (panels above each other) and how many columns (panels horizontally next to each other) will you have?

    Here's my system, notice I have 4 rows high and 7 columns long and my panels are laid out in landscape orientation..
    https://www.homesteadingtoday.com/threads/my-new-solar-array.564775/

    Do you have a water bucket level or laser level? You will absolutely need one.. if you don't have a laser level (I don't like them), you can easily make a water bucket level for just a few dollars..

    How are you setting up your power components? Will your battery bank be next to the solar array or located some distance from it? Knowing what size wire to run from the array to the home is very important and it depends on the voltage and amperage.. wire that is undersized will cost you in the long run in voltage drop losses..
    (and don't even think about using aluminum wire)
     
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  3. MontanaCowboy

    MontanaCowboy New Member

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    Due to need to run generators throughout the day anyway (including 3 phase for my shop) I figured I needed around 3KW to run the house so I over-sized slightly. My refrigerator and freezers are propane powered and draw no AC current. I heat with wood and propane, cook and heat water with propane, and air conditioning is a very short season up here in the mountains. For the most part the electricity is to run a TV once in awhile, air purifiers and the security system with cameras and satellite internet. What I like about this system is that it's supposed to be ready for expansion if I find that I need more.


    In the original post I shared the generic link to the system but mine includes the upgraded XR1000 rails. Here is my actual invoice:

    [​IMG]



    I'm definitely not afraid of the labor part; I just want to have the engineering right the first time because if it isn't exactly right the first time, my OCD will require me to rip it out and start over. ;)


    My slope is almost perfectly due true south. I'll have to come off slope slightly but not much at all and I doubt most would even notice.


    I'm glad to know that it's somewhat normal. It took me two days just to get everything unpacked and inventoried.


    I did get all the required mounting hardware with the kit. I guess the website link doesn't show everything in the kit. In fact, they sent me the kit made for the larger system so now I already have the hardware to expand and only need more panels and pipe.


    This is more along the lines of what I needed to know. It appears there are 5 columns of 3 panels each with 3 panels wired in series and then paralleled with the columns.


    Holy Hell you have a nice setup! Yours is the system I hope mine grows up to become!


    I do use laser levels and have many commercial grade (we used to build overpasses and bridges).


    My panels will be roughly 75' away from the charge controller and I plan on running 4 gauge copper wiring to it. I want to over-size everything to facilitate eventual expansion.

    Hey, thanks much for all the feedback! I often find far more value in forums like this than company tech support.
     
  4. Murby

    Murby Well-Known Member

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    Ok.. What a relief.. you didn't get ripped off.. It looks like they gave you decent pricing on the package as a whole.. If it wasn't for the discounted batteries, you'd have gotten taken.. your pricing is still a bit high but nothing that would send me crying to bed over..

    3 panels in series is just around 100 to 120 volts DC (about ~35 to 39 volts per panel).. 5 paralleled strings is going to give you around to 35 to 40 amps (5 strings pushing around 7.5 amps per) on 4 ga wire rated for 75 amps or so that has to run 75 feet.. There's no room for expansion there unless you kick the voltage up.. 4 ga wire, while capable of 75 or so amps, will incur massive power loses over those distances when you start loading it up with amps. My general rule is never go over 30% capacity at those distances.. not when you're trying to use the sun to generate power anyhow..

    So, that said, if you're going to dig a trench, you should probably bury an extra cable for future expansion so you don't have to dig twice... or install a big grits conduit pipe capable of taking another set of cables. You might also want to install a separate conduit for ethernet communications (Cat5 cable) because most solar equipment these days makes use of that stuff...

    For reference, my inverter sends 25amps @ 240 volts back to the house ( about 140 feet), and I used 4ga copper cable to keep my power losses below 1%.

    But you're good.. you're on the right track.

    I have to run to the store but I'll fire up my autocad and see what kind of layout for your posts you should have. If you give me your zip code, I can do the pvwatts work and then work that into your setup so you'll know exactly what elevations you'll need.

    If you're going 3 panels tall, your front to back pole spacing should be around 7ft-6 inches if I remember the ironridge stuff correctly.. Double check that figure. Do you have any idea of what size concrete piers you're going to use underground? Mine are 22 inches diameter below ground and I went down a full 65 inches below grade.. so don't go cheap here.. the wind load sheer on these things is mind boggling..

    Your next step is to set up a couple of strings that run the entire length of your array plus 10 feet on each side to give you room to work.. The strings should represent the low side and high side support columns. Double check to make sure they are parallel and then use your laser to map out the elevation changes. If you have any east to west differences, that will complicate things but we can take care of that.. it just adds a lot of extra labor taking and double checking measurements...

    Take a look at the first picture in my thread and notice how I laid out the grid.. The first thing you need to do is to put up those two longest strings to mark the line for the front and back piers. Don't worry if they aren't level to the ground.. we're not worried about that yet.
     
    Last edited: Sep 8, 2017
  5. MontanaCowboy

    MontanaCowboy New Member

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    The mentioned 75' is an estimate to the farthest panel, and I wasn't sure so I used the longest distance. The actual combiner box will be around 50' from my charge controller. I won't hesitate to go larger though, if recommended for expansion.


    Thanks much! I'll take your advice and bury the additional cables.


    Thanks much, again! 59072 is my zip code.


    I had originally intended to dig an 18" hole 4' deep, but am not opposed to going deeper. The diameter would require buying a bigger auger, but I'm not opposed to doing that either.
     
  6. Murby

    Murby Well-Known Member

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    You want your array tilted 39 to 40 degrees.. both inputs produced the same amount of power.

    Your 15 panels (295w each) will produce 6480 kWh per year after accounting for average historical weather patterns and 14% system losses.
    For reference, if you did a really good job on all your connections and used large wire, lets say you could get your system losses down from 14% (PVWatts default setting) to a low 12%.. that would allow you to produce 6632 kWh per year.. A difference of 152 kWh every year.. At the end of 10 years, that's 1520 kWh's you would save..

    If you're wondering, the 14% losses are not all electrical.. They account for dirt and grime build up, some snow, bird crap, imperfect electrical crimps, electrical line losses from cable runs, and a host of other stuff.. And yes, the PV Watts model is awesome..
    As it stands, for almost a month worth of record keeping, PV Watts calculated my production to within 0.03%.. That's crazy eh? I'm putting out 99.97% of what they said I would put out for these specific days in August and Sept..

    I have a client in Cody and I remember he said electricity there was really cheap.. something like 10 cents/kWh... so it works out to around $152 saved over 10 years.. Do you know the Boreen family?
    Over on my side (Michigan), electricity, after all the BS taxes and other stupid charges, is more like 16 cents/kWh so going with larger cable was a huge savings that would come back to me in only 6 years.

    What kind of soil do you have there? Is it full of rocks or sandy loam or clay or what? It makes a difference to how much concrete you need to pour. In my area, we have great farming soil that is sandy loam for about 3 feet down then becomes a bit clay like.. and we have very few rocks. If I dig a 10 inch trench 4ft deep and 10 feet long, I might get a 5 gallon bucket of rocks larger than a golf ball. That kind of soil demands deep holes and large foundations.

    The next step is for you to put up your strings for the high side and low side piers.. Then map out the elevation changes of the grade between them and I can calculate the height of each of the poles. You'll want to check your east to west elevation too just to make sure you don't have a drop there..
     
  7. Murby

    Murby Well-Known Member

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    The spacing (north to south) between your high side piers and your low side piers is to be 7ft 6 inches.

    The spacing between your piers (east to west) is to be 8 feet. They gave you 8 Ironridge top caps so you have 4 piers on the low side and 4 piers on the high side. That will give you an east to west pier length of 24 feet for a solar array that covers about 27feet 6 inches... This allows the array to stick out about 18 inches beyond the end piers for aesthetic purposes.

    This all assumes your panels are orientated landscape (horizontally like mine).. which I assume is the plan. It is unclear if the Ironridge calculations account for panel spacing between columns. Some people butt the panel columns right up next to each other but this a bad idea as it doesn't leave room for expansion. You should leave at least 1/2 inch between columns... I left a full 1.5 inches between my columns for cooling and to help with the removal of snow.

    Oh ya.. one other piece of advice.. Get a torque wrench and pay attention to the torque values for the fasteners.. This is important because a lot of your fasteners are going into aluminum.. not enough torque and your panels could become kites in the wind... too much torque and you could bend, strip threads, or even rip the aluminum. I bought a small torque wrench that measures in-lbs from my local Home Depot for something like $40. (I couldn't believe I didn't already own one!)
     
  8. wy_white_wolf

    wy_white_wolf Just howling at the moon

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    Hi MC and welcome to the group. Slope of your array is more dependent on when you want maximum production. 45d will be a fair slope for year round production with a fixed array. My advice though would be to set it up more for winter production. With the shorter days and lower angle somewhere around 60 to 70d would be better. Generally you're using more power in the winter (if you don't have AC) because you're inside more. Panels on my cabin are adjustable but I've left them at 60d for the last couple years. With it being weekend only it works fine for us.

    Do you have any drawings on the PV array? If you get me some details I might be able to work something up for pier distances with AutoCAD.

    BTW my cabin is also in 59072. South end of Old Divide Rd.

    WWW