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  • What angle and what size tank

    Hello All
    I am in the process of building a solar hot water , drain back preheater.
    I am now starting to build the frame, that holds the panel. I live in central Ct. What angle and compass angle (?) should I figure on setting the panel?
    Next question:
    The house this is going on is a very small one bedroom, two showers a day no laundry, no dish washer. What size storage, or holding tank will be best ?

    Thank you for any input !
    Last edited by Gutts; 01-10-2014, 04:19 PM. Reason: Spell check

  • #2
    azimuth is 180 tilt = latitude.
    depends on the size of the collector.
    Generally speaking a rule of thumb is about 1.5 gallons of water per Sq ft of collector area.
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    • #3
      Wow that was quick !
      I have one four by eight , for now , so if I use a fifty gallon drum that would work out? If this works out I am going to add another four by eight to it .
      I tried to post a couple of pics but , not now.

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      • #4
        I guess I should get a bigger tank now so I would not have to "remodel" later ....

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        • #5
          Originally posted by Gutts View Post
          I guess I should get a bigger tank now so I would not have to "remodel" later ....
          Unless there are shading or weather effects in early morning or late afternoon, face your panel due South for maximum total heat input.
          If for some reason your hot water usage is heavily biased toward morning or afternoon and your preheat storage is small, you may want to change the direction to favor morning or evening.
          SunnyBoy 3000 US, 18 BP Solar 175B panels.

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          • #6
            Originally posted by Gutts View Post
            I guess I should get a bigger tank now so I would not have to "remodel" later ....
            Make sure your tank can be insulated to keep in the heat.

            Also what are your plans to heat the water if you don't get sun?

            You might want to think about getting a manufactured insulated tank with a small electric heater element.

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            • #7
              Originally posted by SunEagle View Post
              Also what are your plans to heat the water if you don't get sun?
              The OP described this as a preheater system, so I expect that there is another complete heater in the picture.

              Gutts: Just be aware that preheat does not play well together with on-demand tankless heaters, so if you will be using that kind of heater there is a lot more thinking you need to do.
              SunnyBoy 3000 US, 18 BP Solar 175B panels.

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              • #8
                Thank
                I have full southern exposure almost all day . Very little water usage .
                Right now I have oil fired baseboard heat with a hot water coil that heats the domestic . The panels I have we're made Fl., by a real company . I have resurrected one . I am planning on setting it up on a section of staging for now. I live in a very rural area .
                Thank you all for the information
                Next questions :
                Can I use a coil of pex for a heat exchanger ?
                Are the controls I see on ebay , any good?
                Where exactly do the thermo sensors go on the piping (on the panel) but where ?
                This is my take on the plumbing:
                The pump turns on when the sensor(located ?) on the panel hits (?)
                It pumps water up (?) through the panel , the heated water returns to the storage tank
                When the sensor reads (?) the pump shuts down .
                All the water in the panel and plumbing drops back through the open (?) return line and through the pump (?)
                I do know everything needs to be well insulated
                The old/new panel I have is a sheet of thin aluminum backing , with 1.5" of foam, surrounded by a aluminum frame . The piping is copper pressed onto/into aluminum blades. Painted flat black . It has a peice of tempered glass over it . 3/4" copper

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                • #9
                  [QUOTE=Naptown;95592]azimuth is 180 tilt = latitude.

                  Ok ?
                  I got a leval , protractor and square out .
                  Azimuth is 180 tilt = latitude
                  I face the panel due south .
                  I should tilt it somewhere between flat (leval) and
                  Straight up and down ? About where ? 45 degrees ?

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                  • #10
                    General answer is the same angle as your latitude. There may be some seasonal factors that would change that slightly but generally the same as your latidude.

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                    • #11
                      + 5 degrees tilt over latitude won't effect your output much but will affect how easily the snow slides off. In Ct 45 to 50 degrees should work well for you. You lose a slight amount of output in summer but gain a little in winter.
                      Do not use pex for a HX use copper.

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                      • #12
                        We have a 70' array of photo-voltaic panels. During the winter solstice I marked the spots of where the sun's shadow fell.

                        So now I have the exact spot, or row of spots, for the line, of where to build our solar-thermal array.

                        When do I want the greatest heat? During the coldest weeks of the year.

                        What angle should my solar-thermal array be mounted? At the best angle for during that week.

                        I do not care, if the angle is less efficient in summer. In the summer, most of the panels will likely be covered by tarp.



                        I suggest that you want the highest efficiency from your panels to be during the winter's coldest month.
                        4400w, Midnite Classic 150 charge-controller.

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                        • #13
                          Originally posted by organic farmer View Post
                          I suggest that you want the highest efficiency from your panels to be during the winter's coldest month.
                          Unless the situation is so bad that you will end up shutting the system down in mid-winter because it is not contributing a useful amount of heat.
                          A lot depends on the design of your collector. Open black pipe, not so good in winter. Vacuum tube collectors, more likely. Anything else, somewhere in between and will depend on how well you insulate the collector.
                          SunnyBoy 3000 US, 18 BP Solar 175B panels.

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                          • #14
                            Originally posted by inetdog View Post
                            Unless the situation is so bad that you will end up shutting the system down in mid-winter because it is not contributing a useful amount of heat.
                            A lot depends on the design of your collector. Open black pipe, not so good in winter. Vacuum tube collectors, more likely. Anything else, somewhere in between and will depend on how well you insulate the collector.
                            You are designing a system to provide heat.

                            If your system can not provide a useful amount of heat, then your design was a failure.

                            What angle you set the panels at, will define what week of the solar year, the panels will work best.

                            I want the greatest amount of heat, on the darkest day of the solar year.

                            I want the panels to be the least effective in the summer. Because that is when we want the least heat from them.
                            4400w, Midnite Classic 150 charge-controller.

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                            • #15
                              Originally posted by organic farmer View Post
                              I want the greatest amount of heat, on the darkest day of the solar year.
                              .
                              I have calculated the requirements for solar HW space heating for the northeast numerous ways in the past with flat plates & evacuated tubes. December, january, and 1/2 of Feb. just cannot supply a system with sufficient BTU'S . Even a small house requires 50k BTU per hr at 10 degrees. 50 k btu per day during those month's requires a large array. I try to stay under 160 sq. ft of panels because of cost vs payback. Even 160 sq ft if not heating a pool in summer is a stretch.
                              It seems like a waste to have panels idle in the summer month's. A good design balances a usable size array with seasonal effectiveness, and installation cost.

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