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solar collector in garden / possibly / unsure of pipe insulation

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  • #16
    Originally posted by LucMan View Post
    Pex ratings are 80 psi at 200 F. 100psi at 180 F extrapolating you get 240F at 40 psi. Selecting the correct T&P valves is extremely important.
    If you connect to the collectors with a minimum of 8 ft of copper tubing you will be ok. There would have to be multiple failures in the system safety controls before the pex could fail.
    Probably so - however that is an extrapolation you should never make. A stagnant panel can be well over 200°F. My hot water tank runs 90°C all summer.
    [SIGPIC][/SIGPIC]

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    • #17
      Originally posted by LucMan View Post
      Pex ratings are 80 psi at 200 F. 100psi at 180 F extrapolating you get 240F at 40 psi. Selecting the correct T&P valves is extremely important.
      If you connect to the collectors with a minimum of 8 ft of copper tubing you will be ok. There would have to be multiple failures in the system safety controls before the pex could fail.
      Starting from only two points, you have no reason at all to think that a linear (or inverse) temperature to pressure relationship exists. For interpolation, you at least know that the result will be somewhere between the two data points. For extrapolation, you can get into deep trouble very quickly.

      As an example, consider an extrapolation of metal shear strength versus temperature. There is a really sharp bend in the curve near the melting point.
      SunnyBoy 3000 US, 18 BP Solar 175B panels.

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      • #18
        Thank you again to everyone for your recommendations.
        - CPVC or copper - but not PEX
        - Allowing for thermal expansion
        - Ensuring about safety
        - Hire a professional for these.

        However, I'm still hoping for guidance on the single initial question whether I should run with this or not? Based on the anticipated potential heat loss from the insulated pipes? I'm not looking for precise calculations, just educated ball park figures. Would it be 5%, 10% 30% heat loss? Just enough heat loss advice to pursue it, or kill it.

        trench8.JPG

        A = Styrofoam or cold cell foam
        B = Leak detection
        C = Radiant insulation, foam layer
        D = 300mm PVC drainage pipe
        F = Gravel trench fill

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        • #19
          Originally posted by oemodm View Post
          Thank you again to everyone for your recommendations.
          - CPVC or copper - but not PEX
          - Allowing for thermal expansion
          - Ensuring about safety
          - Hire a professional for these.

          However, I'm still hoping for guidance on the single initial question whether I should run with this or not? Based on the anticipated potential heat loss from the insulated pipes? I'm not looking for precise calculations, just educated ball park figures. Would it be 5%, 10% 30% heat loss? Just enough heat loss advice to pursue it, or kill it.

          [ATTACH=CONFIG]4228[/ATTACH]

          A = Styrofoam or cold cell foam
          B = Leak detection
          C = Radiant insulation, foam layer
          D = 300mm PVC drainage pipe
          F = Gravel trench fill
          I'd not use Styrofoam - temp. limits.

          Finally, I'm having a hard time imagining a way to make this anywhere near cost effective. This may be gross overkill in the insulation dept.

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          • #20
            take a look at what was used in the Solar Shed http://www.builditsolar.com/Projects.../solarshed.htm
            maybe you will get some ideas of what works for others
            Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
            || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
            || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

            solar: http://tinyurl.com/LMR-Solar
            gen: http://tinyurl.com/LMR-Lister

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            • #21
              Originally posted by J.P.M. View Post
              I'd not use Styrofoam - temp. limits.

              Finally, I'm having a hard time imagining a way to make this anywhere near cost effective. This may be gross overkill in the insulation dept.
              I understand. I will wait a little longer, see if any educated ball park figures with regard to heat losses come up. It will determine if I do this, or, double up on west/east roof.

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              • #22
                Here is a link to Armacell insulation, available in wall thickness from 3/8" - 1". (Losses can be calculated from the spec sheet. )
                There will be losses no matter what insulation you use. The question is how much money are you willing to spend on reducing those losses.

                https://www.google.com/url?sa=t&sour...Y00vmXbmJtzpjw

                The pipe of your choice can be run inside 4" nonperforated drainage pipe insulated with armacell, glued at all butt joints.
                Insulation Wall thickness over 1" in my opinion would be a waste of money.

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