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Current radiant setup

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Hi,

I’m having issues with my current radiant system after years of it seemingly working properly. I tried replacing the pump but same problem of no heat. The gauges show water flow through all the zones but it’s just pumping cold water and the gauge on the outlet of the mixing valve shows cold. The gauge on the hot supply to the mixing valve is hit but then it’s cold coming out of the mixing valve.  Before I replace the mixing valve I wanted to run this setup by everyone.  To me it seems like the system is piped incorrectly with the pump seemingly bypassing the mixing valve pulling return water straight into the supply before hitting the mixing valve but it had worked for many years so maybe I’m wrong…?

Any thoughts or help on if I need to have this setup all redone or if it is correct and may just be a faulty mixing valve. 

Comments

  • Alan (California Radiant) Forbes
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    Do you have a pressure gauge? What does it show?
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • Flyingpoet
    Flyingpoet Member Posts: 4
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    Boiler pressure gauge is 25psi but there are no other pressure gauges. The only gauges on the radiant are the supply, mixer, and return temperatures and the GPM flow rates on each zone. Supply temp reading 120F, mixer temp reading 62F, return reading 60F and flow rates are .5GPM to .75GPM depending on zone. If I unplug the circulating pump the flow rates go to 0. 
  • hot_rod
    hot_rod Member Posts: 22,158
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    Mixing valves do stick from time to time. The flow meters indicate flow moving through the loops. What temperature is the boiler running?
    You may have enough valves around it to isolate and disassemble without a complete draindown. Does the red knob turn easily?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Flyingpoet
    Flyingpoet Member Posts: 4
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    The boiler is running 160F-180F. Yes the red knob turns easily. It’s turned now to the highest set point temp but still isn’t raising the temperature of the water flowing in the radiant system. I can replace the mixing valve but also just wanted to confirm that the setup with the pump being parallel to the mixing valve is acceptable?

     I mean it did work before but it just seems to me like the pump should be in line/after the mixer valve and I can’t figure out how the current configuration would work properly…I was hoping to get confirmation from the forum that this setup makes sense. 
  • Jamie Hall
    Jamie Hall Member Posts: 23,324
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    The pump orientation is a little odd, I'll agree -- but it should work if the mixing valve is working properly. And it would be my guess that it isn't. Do you have, or have access to, a good IR thermometer? If so, compare the temperature at the two inlets to the mixing valve and the outlet.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Alan (California Radiant) Forbes
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    That pump is doing nothing to draw water through the mixing valve. The pump bypasses the mixing valve. The pump should be located on the mixed outlet of the mixing valve.

    You say it worked before, but something's not right here.
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • Flyingpoet
    Flyingpoet Member Posts: 4
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    Alan, that’s exactly what I think….i really don’t understand how it worked properly for the last few years or why it was installed that way. 
  • hot_rod
    hot_rod Member Posts: 22,158
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    That looks like a factory built mixing module , possibly from Watts since it connects directly to their manifold spacing?

    If it has worked properly for years??

    Id remove the pump, check impeller, and rebuild the mix valve. Two fairly easy tasks
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,006
    edited February 25
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    There are some blue handled ball valves hiding behind the first vertical pipe on the right. Are they open or closed ?

    And why is that Legend valve in the foreground closed?
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab