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  • Equipment and design advice

    Aloha,
    I am a DIY enthusiast and recently acquired (got them for 150$) three 4x10 solar hot water panels. Have been learning the lingo and systems from this site and Google! Would like to power my outdoor shower to start saving on the elec. bill and then hook up into the house after I learn more. The system is in Hawaii, plenty of sun! Want and need the SIMPLEST system possible. (it is hard to get parts so the less part the better)

    Could I get some advice:
    1. on the type of pump I could use. I have a separate solar panel thats is a 12 volt. prolly about ten watts . Pump during day and idle at night.
    Is something like this pump ok? I do intend to put them on the roof (one story house) Not sure how to figure out how much head I need. It is rated about 5 feet but (heres my confusion) once the system is primed does it matter? The water coming down to the tank helps it along???

    link for pump = http://www.topsflo.com/special-pumps...tion-pump.html

    2. I need a storage tank. Will find a used home tank and convert it. Do you all pull out the heating elements to use as input/output to panels or something else?

    3. Pressure. Can the system get too hot for the storage tank.

    4. Potable water. I would like to power the house with the system once I get a grasp on it. What safety precautions to I need to take. I assume the panels did not have glycol in them as they were from the tropics.

    5. Drainback. Will it be a problem?







    A diagram of the plan so far....... and the panels!

    IMG_9359.JPGIMG_9261.JPGIMG_9262.JPG
    Attached Files

  • #2
    with the heating panels above the tank, you need a way to halt nightime thermalsiphon
    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

    Comment


    • #3
      If no freezing, I'd consider putting the tank above the panels and making the system a thermosiphon type, and thus eliminate the pump altogether.

      See builditsolar.com for lots of ideas and info on some plumbing requirements like an expansion tank, relief valves for press. & temp., valving, etc.

      Think safety first !! and always.

      Comment


      • #4
        The first consideration should be how to control the temperature of your water for safety reasons. Hooking up those 3 panels will easily boil water in the summer creating dangerous pressure on your system.
        One panel should be good for 60 gallons of water at 130+ degrees. For safety reasons I recommend drain back systems because when the max water temperature is reached the main pump turn off and all water drains out of the panels preventing overheating and dangerous pressures and temps. There are additional costs associated with this type of system but it should be safe.
        Take a look at the SRCC web site and search out your panels to determine how many gallons of water they will safely heat in your climate area.

        Comment


        • #5
          N0t going to put tank above the panels due to weight on roof.

          I will to start with one panel and a 80 gallon tank to prevent getting to hot, thx for the advice!

          I was advised to use something like this check valve above the pump to prevent thermosiphoning at night. The valve is teflon coated to prevent fouling.
          Will one check valve above the pump line be enough?

          Screen Shot 2017-11-07 at 9.13.24 AM.png

          http://www.nibco.com/Valves/Check-Va...Threaded-Ends/



          Any advice on the brand of pump? The el sid is 320$ out here. The topsflo is 60$ on amazon!

          Anyone convert a used elec. tank to use with the panels?

          Aloha,
          Michael

          Comment


          • #6
            I posted the wrong link. This is the lead free version.

            http://www.nibco.com/Valves/Check-Va...Disc-Threaded/

            Comment


            • #7
              Pump needs to be stainless or bronze and capable of overcoming system head pressure, some calculations are needed to select the pump.

              Comment


              • #8
                Originally posted by Mbjah808 View Post
                N0t going to put tank above the panels due to weight on roof.

                I will to start with one panel and a 80 gallon tank to prevent getting to hot, thx for the advice!

                I was advised to use something like this check valve above the pump to prevent thermosiphoning at night. The valve is teflon coated to prevent fouling.
                Will one check valve above the pump line be enough?

                Screen Shot 2017-11-07 at 9.13.24 AM.png

                http://www.nibco.com/Valves/Check-Va...Threaded-Ends/



                Any advice on the brand of pump? The el sid is 320$ out here. The topsflo is 60$ on amazon!

                Anyone convert a used elec. tank to use with the panels?

                Aloha,
                Michael
                As LucMan writes on pump (and other materials).

                Usually, systems are sized (that is area/panel X # of panels) and oriented (azimuth and tilt) as application available if a roof mount to meet the hot water load or as much of it as the design requires or can be done in the space and orientations available. Then, the flow rate is calced' for best trade off between pumping cost, including initial costs and (usually) much lower pumping costs, thermal efficiency, and system design for best/longest trouble free design/maint. Then, the pump is sized/selected based on pump curves and the estimated pressure drop through the system collectors, piping and valves, etc. It's a bit of an iterative process.

                Others will probably think this way too high for a flow rate, but for many sound fluid mechanical and thermal reasons probably boring to most, I pump a minimum of ~ 1.7 GPM through 2 ea. 4 X 8 collectors plumbed in series. In San Diego, on a sunny day in spring/fall, I can raise the temp. of 80 gal. of H2O by 110 F. or so, if I don't cover at least 1/2 of one of the collectors.

                With that in mind, in HI, 3 ea. 4 X 10 collectors (or close to 2X my size) will probably boil 80 gal. of water most of the year on a sunny day. Not safe and a waste. After load sizing, including considerations for use patterns, I'd consider either using 2 panels and know 1 of them will be intentionally covered a good portion of the time, or use 2 ea. 80 gal. tanks, or one 120 gal. tank, or, 3 collectors tilted ~ 45 deg. or thereabouts and a 120 gal. tank.

                Or.... ?? Lots of other possibilities.

                I'd suggest you learn something of piping design and solar thermal engineering. There are lots of ways to construct designs that look good on paper but will be dangerous, not to mention inefficient and probably failure prone.

                Also, don't forget wind, seismic and other important structural requirements.

                There are a lot of details important details necessary for a safe design you sound unaware of that cannot be covered in the limited space available here.

                Take what you want of the above. Scrap the rest. Just think safety. What you don't know can and will hurt you. It'll also cost you money and time.

                Comment

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