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how to divert from primary to secondary storage tank- components needed?

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  • how to divert from primary to secondary storage tank- components needed?

    I am unsure about what kind of devices are needed to be able to take heat from a solar thermal (glycol closed-loop) setup, to heat domestic water in a 40-gallon storage tank up to 120F, and then have the solar thermal heat redirected into a 400-gallon storage tank. What contraption would you use to detect when the temp has reached 120f in the primary tank, and divert that heat to the larger secondary tank?
    The 40-gallon tank is a System 2000/ Energy Kinetics with a small external plate heat exchanger. The heat exchanger in the 400-gallon tank is a coil of 3/4" copper., and the heat from that tank is harvested to preheat the domestic hot water as well as radiant space heating via pex tubing. I don't have the solar system up and running yet. I'd like to integrate that primary tank so that I've got 40 gallons of 120F water at the ready, but I don't want it to get hotter than that because it needs to run through my on-demand propane water heater, and it won't accept water over that temp, and I don't want the risk of scalding.
    Diagrams and links to components needed would be much appreciated. thanks.photo (14).JPG

  • #2
    Originally posted by Jarvis View Post
    I am unsure about what kind of devices are needed to be able to take heat from a solar thermal (glycol closed-loop) setup, to heat domestic water in a 40-gallon storage tank up to 120F, and then have the solar thermal heat redirected into a 400-gallon storage tank. What contraption would you use to detect when the temp has reached 120f in the primary tank, and divert that heat to the larger secondary tank?
    The 40-gallon tank is a System 2000/ Energy Kinetics with a small external plate heat exchanger. The heat exchanger in the 400-gallon tank is a coil of 3/4" copper., and the heat from that tank is harvested to preheat the domestic hot water as well as radiant space heating via pex tubing. I don't have the solar system up and running yet. I'd like to integrate that primary tank so that I've got 40 gallons of 120F water at the ready, but I don't want it to get hotter than that because it needs to run through my on-demand propane water heater, and it won't accept water over that temp, and I don't want the risk of scalding.
    Diagrams and links to components needed would be much appreciated. thanks.
    Well, you need one or two controllable valves to change the flow path from the external heat exchanger to the coil.
    But I rather doubt that the copper coil inside the 400 gallon tank meets the standards required for separating your glycol loop from domestic hot water.
    Instead you could simply use a temperature sensor and simple controller to pump water between the 40 gallon tank and the 400 gallon tank once the 40 gallon tank reaches its upper limit temperature.
    You could probably get away with just using one or more thermostatically controlled valves and the same circulating pump that is used with your plate heat exchanger. (Or is the tank side of that just convection circulation?)
    SunnyBoy 3000 US, 18 BP Solar 175B panels.

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    • #3
      Try these
      The pdf file has diagrams of many different options you can use.
      You will need at least one 3 way valve and a differential controller to operate everything.
      Attached Files

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      • #4
        I have attached a diagram of what I am attempting to do, if any of you would be willing to look it over and offer suggestions. thanks
        Attached Files

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        • #5
          The most convenient solution is probably diverting valve (3-ways). No need electricity, self actuator, temperature controlled.
          When the temperature of preheated water lower than 120F, the hot water port fully closed and the cold water port fully opened in the diverting valve. When the temperature of preheated water higher than 120F, the hot water port fully opened and the cold water port fully closed in the diverting valve. The hot water can be used
          It is easily installed valve in your system.换向_副本.png换向阀_副本.png

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          • #6
            Originally posted by Davis Jin View Post
            The most convenient solution is probably diverting valve (3-ways). No need electricity, self actuator, temperature controlled.
            When the temperature of preheated water lower than 120F, the hot water port fully closed and the cold water port fully opened in the diverting valve. When the temperature of preheated water higher than 120F, the hot water port fully opened and the cold water port fully closed in the diverting valve. The hot water can be used
            It is easily installed valve in your system.[ATTACH=CONFIG]4424[/ATTACH][ATTACH=CONFIG]4425[/ATTACH]
            If you go that route, I'd suggest additional valves (preferably flanged, but screwed will do). Sanitary piping w/something like Triclover connections w/quick release is ideal but would involve changing a lot of stuff and is quite expensive for the sake of a few valves. The best of any valves will need service/changeout at some point and the additional valves will serve as isolation for the 3 way which, depending on quality, usually tends to bypass/leak between streams after a time. You will also find the additional valves useful as throttling devices to fine tune the outlet temp. My experience w/temp. control for valves of the type pictured is less than ideal.

            When it comes to piping and valves, keep the valves to a minimum for purpose, and spend the money you save on reduced # on quality valving. Cheap valves are one on the best examples of false economy I know of.

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            • #7
              Originally posted by J.P.M. View Post
              If you go that route, I'd suggest additional valves (preferably flanged, but screwed will do). Sanitary piping w/something like Triclover connections w/quick release is ideal but would involve changing a lot of stuff and is quite expensive for the sake of a few valves. The best of any valves will need service/changeout at some point and the additional valves will serve as isolation for the 3 way which, depending on quality, usually tends to bypass/leak between streams after a time. You will also find the additional valves useful as throttling devices to fine tune the outlet temp. My experience w/temp. control for valves of the type pictured is less than ideal.

              When it comes to piping and valves, keep the valves to a minimum for purpose, and spend the money you save on reduced # on quality valving. Cheap valves are one on the best examples of false economy I know of.
              I agree. At this point I am switching from the problematic Honeywell mixing valves and trying the Callefi. I hope they are more reliable, I'm tired of the callbacks.

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              • #8
                Originally posted by LucMan View Post
                I agree. At this point I am switching from the problematic Honeywell mixing valves and trying the Callefi. I hope they are more reliable, I'm tired of the callbacks.
                LucMan the Caleffi have been an absolutely bulletproof unit, well worth the small premium. As a wholesaler I have sold thousands with only 2 -4 returns in 5 years. The only drawback is they have a maximum outlet temp of 155F which does not always fit everybody's intended use.

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