Pole Mount Foundation Options

We are getting ready to install a few top of pole mounts for a new array. I have seen the foundations done a few different ways. One way is to pour the concrete to about an inch or so below the ground surface, cover the pour with dirt and seed it with grass. The other way is to use a concrete form such as a sonotube and pour the concrete to a few inches above the ground. We are using galvanized poles and have no problem painting them. Is there a big difference in these two methods. Is one way significantly better than the other? My common sense would make me think that pouring the concrete to a few inches above the ground would be less likely to corrode, but does it really make enough of a difference to warrant all the extra work/materials needed to accomplish this? Homepower had a good article on installing pole mounts using the method of pouring to an inch or so below ground and covering with dirt, and that seems to be a very straight forward approach that in my opinion looks better (Aug/Sept 2005 issue).

Comments

  • peakbaggerpeakbagger Solar Expert Posts: 341 ✭✭✭
    Re: Pole Mount Foundation Options

    Mine sticks out of the ground by 8" and I sloped the concrete away from the pole so that water wouldnt pond. I wanted all the stiffnees I could get and when you are cantilevering a load, that extra length of concrete stiffens things up. When I upraded to a larger array on the same pole I noticed that I got some wind induced vibration where the array tends to vibrate rotationally in the right wind conditions. My solution was to run a brace from the bottom edge of the array down to a bolt on the side of the concrete, I am not sure how it would look. Then again witth the requirement that the array wiring has to be "inaccesible" and the slim availaility of panels with conduit, many juridictions basically require a fence around the base of the array so that would be far more intrusive than the concrete.
  • vtmapsvtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Pole Mount Foundation Options
    logaholic wrote: »
    My common sense would make me think that pouring the concrete to a few inches above the ground would be less likely to corrode, but does it really make enough of a difference to warrant all the extra work/materials needed to accomplish this?

    I've never seen or heard of the 'below ground' method without a sonotube, except in that HP article. If you don't use a sonotube, it would seem to me that you would be pouring more concrete than you need, unless you can dig a perfectly cylindrical hole of the right size. I do agree that the above ground method would be less liable to corrode. Also, I don't see a need to paint the pole if it is galvanized.

    BTW, that home power article you referred to was part 1. The next issue had part 2.
    A link to both parts can be found here: http://forum.solar-electric.com/showthread.php?14721

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • vtmapsvtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Pole Mount Foundation Options
    peakbagger wrote: »
    Then again witth the requirement that the array wiring has to be "inaccesible" and the slim availaility of panels with conduit, many juridictions basically require a fence around the base of the array so that would be far more intrusive than the concrete.

    I did not put a fence around my panels, and I believe it was the only non-code compliant decision that I made in my system. (I live where there is no requirement to follow code) --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • logaholiclogaholic Registered Users Posts: 9
    Re: Pole Mount Foundation Options

    Thanks for the thoughts. We didn't need a permit for the panels so I don't think they will be inspected but I plan on making the wires as inaccessible as possible. I was able to dig perfectly round holes with a 36" tree auger and skid steer, so without a sonotube I will not be wasting much concrete. I'm having a difficult time locating sonotubes and they are expensive for what they are, and the wife would much prefer not having a concrete slap protruding from the ground, so we're still trying to weight the options...
  • vtmapsvtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Pole Mount Foundation Options

    How about making a cone shaped top so that only a small cone protruded above the ground? --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • solarvicsolarvic Solar Expert Posts: 1,071 ✭✭✭✭
    Re: Pole Mount Foundation Options

    I have installed a few satelite dish,s and uninstalled a few also. It was easier to take down the pipe that had the cement a couple inches below ground. Just dig up a couple inches of dirt dirt and cut off the pipe with an acetylene wrench. Cover up with dirt and plant some grass seed. So yhat is the way I installed all my satelite dishes and my top of pole racks. Also I don,t like perfect circle holes and usually put a wider spot on one side to be sure the cement won,t turn in the hole. :Dsolarvic:D
  • offgrid meoffgrid me Solar Expert Posts: 119 ✭✭
    Re: Pole Mount Foundation Options

    Two quick things. If possible you should bell shape the bottom of the hole. This gives more support, and helps to hold the concrete from heaving up with heavy ground frost. Where I live we always hold the concrete a few inches below ground level. This helps insulate it a little and stops it from drawing the cold from the air down and freezing the ground around the concrete first. Thus causing it to heave. Just my experience.
    Ned
  • VicVic Solar Expert Posts: 3,152 ✭✭✭✭
    Re: Pole Mount Foundation Options

    Hi logaholic,

    You did not mention the number and size of the PVs that you are considering installing on the pole mounts.
    AND, your post was really asking about above/below grade concrete.

    But, for a pole mount, believe that it could be difficult to have enough reaction mass to offset the mass and possible sail area, using Sono Tube, IF the area of the PVs is significant. Some of the 'wasted" concrete could really be needed if there are very many PVs at all, and you have very much wind. This is all relative.

    How many PV modules or what size are you considering? The height above the concrete base also affects the amount of concrete that you need to keep the pole vertical. Ideally, pole mounts should be designed or at least reviewed by a PE, even if it is not required by your jurisdiction. You might be able to find on-line examples of engineered solutions that would apply to your soil and wind conditions for the total area of PVs you are considering.
    Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • Gitchee Gumee KidGitchee Gumee Kid Registered Users Posts: 19
    Re: Pole Mount Foundation Options

    [th_IMG_0157-1.jpg

    click on thumbnail pics to enlarge
    > there are 20 photos of the installation . Go to#1 ( click "previous ")

    GGK
Sign In or Register to comment.