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Radiant Heat Loop

Hello, I have a boiler with multiple zone valves that feed radiators with one main circulation pump on the supply side of my boiler. I added a radiant loop with a mixing valve with an additional zone valve. My question is, do I need a separate circulating pump on the mixed side of the mixing valve that feeds my radiant loop?

Comments

  • Dave Carpentier
    Dave Carpentier Member Posts: 577
    Possible to make a sketch or post some photos ?
    30+ yrs in telecom outside plant.
    Currently in building maintenance.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,513
    YES. You need to get the mixed water to flow out of the mixing valve. The system pump can't do that.

    I have also found that you probably didn't need the zone valve. I did the same thing 20 years ago. Had a zone valve for future use when I installed my Buderus Boiler. 2 years later I installed some radiant floor heat with a mixing valve and pump. About 10 years ago I had a Zone valve failure and used the radiant zone to fix the problem temporarily. Turns out the thermostat operates the pump and heats the radiant room. When the circulator is off the room heat stops. So I never put the replacement head back on that zone. Still on the shelf for future use.
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • rmorrisjr24
    rmorrisjr24 Member Posts: 3
    Here is drawing, it’s a little crude, but should give the info needed.
  • neilc
    neilc Member Posts: 2,663
    yes, you need that pump there,
    known to beat dead horses
  • hot_rod
    hot_rod Member Posts: 21,820
    You need a pump, one with an integrated check valve, then you would not need the zone valve
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • rmorrisjr24
    rmorrisjr24 Member Posts: 3
    Thanks guys!
  • Brian S
    Brian S Member Posts: 12
    Question about this application guys. When piped in this fashion with pump w/IFC after the mixing valve. Will both pumps need to operate simultaneously in order to heat the radiant zone or can the radiant pump heat this zone independently.
  • hot_rod
    hot_rod Member Posts: 21,820
    This article show 3 options for adding a small radiant zone to a high temperature boiler system.

    https://www.pmmag.com/articles/84495-a-little-floor-warming-please-john-siegenthaler
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream