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Pool heating with PV and 12vdc pump through Fafco panel?

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  • Pool heating with PV and 12vdc pump through Fafco panel?

    I just want to run this past the experts before I put too much effort into the project.
    I am setting up a small battery charging solar system that will power a 12vdc pump that will move pool water through a Fafco heat exchanger and back to the pool.
    the pool is small and I will have a black walk-on cover to help heat.
    I have 4 older 55W panels that I plan to wire in series parallel to charge the sla batteries. The panels are old and the stickers are gone so I will have to do some testing to see what they are capable of.
    I have a 30A ebay charge controller that I hope will do the trick. It has contacts for "load" but I assume that will energize only when the panels are not producing?
    I then plan to install a discharge protector for the batteries.
    the pump motor will then take its power from the discharge protector. I plan on having a thermal switch mounted in the outlet of the Fafco to switch the pump on only when the temp is higher than the water in the pool.

    Things I still need to determine:
    -running current of the pump
    -pv output in various conditions
    -battery size

    anything else?

  • #2
    Why does the pump need to run when there is no sun? If your "Fafco" is a thermal solar panel, why not just get a pump that can be directly connected to a PV solar panel? sun comes up, pump starts on low, mid day pump runs at max flow. adding consumables like batteries just complicates things

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    • #3
      My concern is that if I run the pump directly from the pv, the system will start pumping before the Fafco panel has actually warmed. I guess this really depends on how much heat is lost in the pool overnight. I want to maximize the solar but I don't want to cool the pool with a panel that is intended to heat it. Right?

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      • #4
        Originally posted by Chaz D View Post
        My concern is that if I run the pump directly from the pv, the system will start pumping before the Fafco panel has actually warmed. I guess this really depends on how much heat is lost in the pool overnight. I want to maximize the solar but I don't want to cool the pool with a panel that is intended to heat it. Right?
        As long as the PV panels and Fafco are in the same orientation, the lost heat from what may be a mismatch in thermal and PV unit operation times will probably amount to about squat, both at A.M. startup and P.M. shutdown. You can also fool with different orientations for the PV and thermal and perhaps better optimize/match operation between the two, but kind of a PITA for what's probably a small, if any gain. On early startup (or late shutdown), you'll lose more process efficiency from mismatch between pump flowrate and heat transfer film coeff., and there's not a lot to be done about it. Long story. I'd not worry about either.

        Except as a learning experience, I'd use the pool pump and divert flow through the Fafco, run the filter pump 8 - 5, call it done and use the panels for other experiments.
        Last edited by J.P.M.; 04-30-2017, 08:42 PM.

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        • #5
          You could consider a small circuit called a "Temperature differential controller" maybe you can find one that runs direct from PV

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          • #6
            Originally posted by Chaz D View Post
            My concern is that if I run the pump directly from the pv, the system will start pumping before the Fafco panel has actually warmed. I guess this really depends on how much heat is lost in the pool overnight. I want to maximize the solar but I don't want to cool the pool with a panel that is intended to heat it. Right?
            How big is your Fafco panel? I read somewhere you need to have them at least 1/3 of your pool area to make noticeable improvement. When running they are supposed to output water only couple degrees warmer than at the input, this way they harvest most energy. How about air temperature? It's not much fun to get out of the pool which is only 3-5 degrees warmer than it would be naturally to be greeted with cold wind.

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            • #7
              Thank you for all of the suggestions so far.
              The Fafco panel is only 4'x10' so I'm not expecting a lot of heating with it anyway. The pool will only be 12'x26' which means the Fafco is less than 1/6th of the pool surface area. I will also have a dark cover and the pool will only be 10,500 gallons and in northern California, the water should be warm enough for swimming from May to Sept.

              I'll set it up initially so the main pool pump will run the Fafco and go from there.

              Sort of off-topic: ever heard of anyone using pool water to cool a house while heating water for the pool? We often get into tripple digits and the pool will never be close to that. I'm thinking of a small heat exchanger and fan inside the house that has cooler pool water flowing through it. The temperature delta would be small but possibly helpful nonetheless.

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              • #8
                Originally posted by Chaz D View Post
                Sort of off-topic: ever heard of anyone using pool water to cool a house while heating water for the pool? We often get into tripple digits and the pool will never be close to that. I'm thinking of a small heat exchanger and fan inside the house that has cooler pool water flowing through it. The temperature delta would be small but possibly helpful nonetheless.
                Good thinking, but the temp. differentials between pool water and interior air are too small to allow equipment small enough to be of practical, much less economically viable use.

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