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hydronic radiant floor relay solution for solar assist

tommcveightommcveigh Posts: 4Member
<span>I think I finally figured out how to wire my solar pump (P1 on attached diagram) feeding my hydronic radiant floors & hot tub, which is fed by a home-built solar tank (450 gallons), and a mod/con boiler (TriangleTube).  If you have experience with such things, please review & let me know if I’m in the right path, or if there is a better way.   My three zones are upstairs (five 300 foot loops), downstairs (four 300 foot loops), and the hot tub heat exchanger.  The call for heat from the hot tub aquastat or either thermostat goes to a Taco SR503-4 three zone switching relay.  This 1) opens the appropriate zone valves, 2) operates the boiler, and 3) powers the Grundfos Alpha (P3) that automatically ramps up or down when zone valves open& close.  The Taco Switching Relay comes with good instructions & seems easy to wire.  My issue is to properly power P1, which adds BTUs to the returning water if available in the solar tank.  Since this solar heat is cheaper, it is introduced into the loop before the boiler’s gas-heated water.  The logic to control P1 needs to be that there is a call for heat AND the returning water temp needs to be less than the solar tank water temp.  Otherwise, the tank would be cooling the water instead of adding heat to it.  I believe the answer is two relays wired in a series & a Delta-T controller.  The hot wire to the P1 only makes a circuit when both the ‘call to heat’ relay is powered AND the Delta-T relay is powered.  I plan to use two Omron </span><span>LY2N AC110/120 relays (normally open).  Is there a better way to do this, such as a delta-T controller out there that contains relay control already in it?</span>


  • ZmanZman Posts: 5,443Member

    From  piping point of view, you are looking pretty good.You will need a balancing valve on the hot tub heat exchanger. Given the different head loss characteristics between the radiant loops and the heat exchanger, the water will scream through the heat exchanger and starve the radiant if left unbalanced.

    It looks like you have decided on a fixed temp system with no outdoor reset?

    How do you plan to tell the triangle tube not to fire when the solar tank is being used?

    I would suggest putting a DPDT relay on the delta t controller. The solar tank circ would be wired to the NO and the Triangle tube terminals would be wired to NC. that way they would never be on at the same time.

    A variable speed circ on the solar tank is a good idea. The Bumble bee has a feature where it will modulate to a specific target temp. The sensor would be on the main piping loop.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • tommcveightommcveigh Posts: 4Member
    specific reason why only one heat source should be allowed to run when there is a call for heat?

    Thanks for the balancing valve idea.  I plan on using the ODR on the boiler.  I will have an iSeries mixing valve on the pipe feeding into the loop from the solar tank.  This will have ODR, and will reduce the solar water temp (mixing with the return water) if it is too hot per the ODR.  This ODR curve will be set to match the boiler’s ODR curve.  The system is designed to operate the solar BTU feed and boiler BTU feed independently.  The solar tank’s heat is added first (if available).  If more heat is needed, the boiler will fire and be fed into the loop also.  Is there a specific reason why only one heat source should be allowed to run when there is a call for heat?
  • ZmanZman Posts: 5,443Member
    2 way street.

    The boiler will heat the solar storage tank when it runs out of energy if you allow it to run simultaneously.

    I think you can do what you are trying to do with 2 separate ODR controllers.

    It would be far easier with a Tekmar Controller managing the whole show.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
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