Radiant Heat Expansion- How?

Discussion in 'Boiler Forum' started by BenGua, Sep 7, 2019.

  1. BenGua

    BenGua New Member

    Sep 7, 2019
    IMG_20190906_080423.jpg IMG_20190906_080453.jpg

    I have a 200K BTU Noritz hot water boiler (max 140F) that supplies DHW directly, and through a heat exchanger heats water for a 1500 sq. ft first floor only radiant heat system. There is a circulator pump just outside the boiler that moves the DHW and a 2nd pump for the radiant water loop. Controlling this is a two zone i-Link (switch relay) controller with the radiant heat system on Zone 1 (& Zone 2 is empty right now). Physically next to the Zone 1 pump is the start where a Zone 2 pump could be added. For reference, I did not install this system it came with the house.

    I am looking to add heat to 2 unheated rooms (each less than 200 sq. ft) . To do this I am considering adding a Tomotoyi HC-20 to each room, but I am stuck how I should do the pumping, zoning, and plumbing.

    - I thinking of adding a 2nd circ pump and a new pex manifold. Then each HC would be a single run off the manifold with a zone valve in the loop.

    - The heat convectors have their own thermostats. If I use zone valves, and connect the HCs to the valves, can I wire both valves to the future 2nd circ pump? My thought process is... If one HC demands heat then pump turns on. If one HC was running and then the other HC wanted heat the 2nd valve would open but since the pump is already running nothing bad happens?

    - With my current switch relay controller, can I have two zone valves wired to a single pump? Or, do I need a three zone system/controller, but 2 pumps (and I would jump Pump 2 and 3 together?).

    Last edited: Sep 7, 2019
  2. Dana

    Dana In the trades

    Jan 14, 2009
    It's fine to have a single "smart" pump that has constant-pressure feedback mode (such as Taco's VR1816) running two zones operating off zone valves, letting the hydro coil thermostats open/close the zone valves. You may need to use 2-zone controller for the control valves to get it to do the right thing in combination with the i-Link SP82 though. Read up on documentation to figure that out. It might be simpler to swap out the existing controller for a multi-zone zone valve controller (along with a zone valve for the radiant.)
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