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Radiant Heating loops not getting hot enough

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smurfy82
smurfy82 Member Posts: 3
edited January 2022 in Radiant Heating
I have recently installed a Navien NCB 240E with 4 radiant zones and 2 baseboard zones although the baseboards are currently not hooked up. I have ensured that none of my loops are more than 300 feet and there are no leaks. Each loop has its own TACO 007 circ pump. The boiler is constatnly short cycling (running for a minute or less and then shutting down for about 3 minutes before starting up again). The navien manifold legs are much warmer than the supply for the loops. I am wondering why I have such low flow or heat exchange. I have tried to bleed the loops a few times and it appears to always have a smooth steady flow before closing and hooking back up leading me to believe its not air bound. The only thing I have heard up until this point is that I put my circ pumps on the return side of the loops when I should have put it on the supply side. Navien claims that shouldnt matter however. Does anyone have any suggestions? Thanks.

I have included pictures.

Comments

  • smurfy82
    smurfy82 Member Posts: 3
    edited January 2022
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    Please check this video for a more complete visual explanation. Thanks very much everyone. https://youtu.be/kJAvkPw4XuE
  • neilc
    neilc Member Posts: 2,707
    edited January 2022
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    you need a circulator on what should be your primary loop, the loop with the expansion tank,
    the boiler heat is going down the manifold leg, over 4 inches, and right back into the boiler return,
    you need something to FLOW past the manifold legs,

    are there other supplies not shown ?
    I see 4, and 2 more return circs up high,
    and only 2 supplies down low,

    and I'm not certain of the primary either,
    more pictures, from more distant
    known to beat dead horses
  • kcopp
    kcopp Member Posts: 4,440
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    You will Never pull enough flow through that mixing valve...
    Injection piping would be best.
    HomerJSmith
  • neilc
    neilc Member Posts: 2,707
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    kcopp said:

    You will Never pull enough flow through that mixing valve...
    Injection piping would be best.

    I kneew there was something else
    known to beat dead horses
  • hot_rod
    hot_rod Member Posts: 22,254
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    You need some repiping work. A better primary loop piping, and some circulator downstream of the 3 way mix valve.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Rich_49
  • HomerJSmith
    HomerJSmith Member Posts: 2,467
    edited January 2022
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    I would have used a Taco I-series setpoint mixing valve. I don't know what the CV of that Taco thermostatic mixing valve is, but I would want the the highest CV that I can get.
  • Zman
    Zman Member Posts: 7,574
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    I would have used a Taco I-series setpoint mixing valve. I don't know what the CV of that Taco thermostatic mixing valve is, but I would want the the highest CV that I can get.

    Why not I Series with outdoor reset? In my mind it is a must with high mass concrete and a good idea in low mass system.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein