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Piping design when two parallel storage tanks used to preheat water.

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  • #16
    I agree - one tank with two heat exchanger coils would serve the purpose nicely

    One coil for the solar and one for the heat pump
    [SIGPIC][/SIGPIC]

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    • #17
      First lower the thermostats on your electric strips to 110 degrees or lower if possible.
      By using a 3 way valve I would heat 1 tank at a time (primary tank) to a set temperature with the solar ( 120 -130 degrees?). Then the 3 way valve would switch to the next tank heating that tanks water. Turn off the circulation between the 2 tanks unless you have sufficient capacity with your heat pump to heat the water to the desired temperature. Then a thermostat could bring on the pump to circulate excessively hot water between the 2 tanks
      refer to page 20 in the attachment for the 3 way valve.
      The 3 way valve would be piped into the outlet of the HX.
      Attached Files

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      • #18
        I like the idea of the three way valve and heating one tank, then the other, but I'm not sure why you guys suggest not heating both tanks from the solar?

        Luke

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        • #19
          Less complicated. Figure out what can fail, and how you work around it. What about frost protection for the solar ?
          Solar is good for preheating the water, and if you get it 80% of the way to HOT, then the electric takes over and finishes it. Heating 2 tanks, the electric (I assume the 2nd heater is electric ??) will try to keep BOTH of them hot, beyond the range of the solar assist.
          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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          • #20
            Alright, well I'll start with the 3-way valve setup.

            I'll just have to figure out how to get a second 3-way valve connected to the controller to dump the excess heat into the geothermal ground loop once the two tanks are hot... Actually, the geothermal heat exchanger loop could just be in series with the high temperature heat dump which is a separate function on the controller.

            LucMan, the manual you attached is quite similar to mine! It must be the same manufacturer controller.

            Now that I've gotten a few posts on this thread, I probably shouldn't have hijacked it

            SR1188 Manual.pdf

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            • #21
              just replying

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              • #22
                Originally posted by LAWindsurfer View Post
                Attached chart shows that water use and gas consumption does not appear correlated. Solar installed December 2010. Unknown if gas consumption goes up in the winter because people take hotter showers or because of increased losses in (insulated) hot water circulation line. Hot water circulation line is heated by gas since it circulates the water in the gas fired water tank. Hot water circulation pump is controlled by sensor on return line except during morning and evening "rush" hours. Pump runs when water at return point drops below 110 oF and turns on when temp rises above 112 oF.

                It seems to me that the reverse parallel connection would only make a big difference if the plumbing between the tanks obstructed the solar water flow by an amount comparable to the obstruction represented by the heat exchanger coils.

                I'm in the process of instrumenting the configuration with max/min thermometers to see if all of the pre-heated water is used up during the night.

                the piping connection should always achieve equal pressure for each tank

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                • #23
                  Originally posted by LAWindsurfer View Post
                  Diagram attached

                  What is meant by "parallel reverse?"

                  Effectiveness of solar hot water heating is being judged by comparing cu.ft. of gas consumption (with correction for BTU content) for three years prior to installation with gas consumption over most recent year.
                  parallel reverse???

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                  • #24
                    parallel reverse not key problem

                    Originally posted by svi View Post
                    parallel reverse???
                    Ideally, parallel storage tanks should be configured such that there is equal flow between the two parallel tanks. My tanks may not be configured for nearly equal flow, but that was not the main problem. The system was originally configured to use heat exchangers built into the storage tanks to transfer the heat from the collector circulation line to the storage tanks. They proved to be very poor an heat transfer. After an external heat exchange was installed, there was a very dramatic increase in the heat transferred from the collector circulation line to the storage tanks. The system has been working just fine and gas use during the summer months has dropped by a factor of two.

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                    • #25
                      thanks

                      thanks forr the info

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