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Thread: Help with hydronic radiant heat

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  1. #1
    DIY Junior Member alfpark's Avatar
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    Default Help with hydronic radiant heat

    I have a hydronic system. I currently have the boiler set @ 160-140 and have my mixing valve going to my radiant manifolds set to 150. I have a delta t of 20, I have 150F heading out of my loops and 130F returning. My floors are warm but I cant maintain house warmth. My stats had been set @ 68 which was comfortable during day and nights of outdoor temps in the 30's and 40's. Now temps in the teens and I cant hold room temps. Some rooms down to 60F and below. Still same out and return temps. Construction is new all rooms are insulated well. System is staple up under 3/4 advantech subfloor and 3/4 engineered hardwood. It has Foil double bubble with an air gap below and R13 below that. Any help or ideas will be greatly appriciated!!

  2. #2
    Journeyman & Gas Fitter Doherty Plumbing's Avatar
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    Quote Originally Posted by alfpark View Post
    I have a hydronic system. I currently have the boiler set @ 160-140 and have my mixing valve going to my radiant manifolds set to 150. I have a delta t of 20, I have 150F heading out of my loops and 130F returning. My floors are warm but I cant maintain house warmth. My stats had been set @ 68 which was comfortable during day and nights of outdoor temps in the 30's and 40's. Now temps in the teens and I cant hold room temps. Some rooms down to 60F and below. Still same out and return temps. Construction is new all rooms are insulated well. System is staple up under 3/4 advantech subfloor and 3/4 engineered hardwood. It has Foil double bubble with an air gap below and R13 below that. Any help or ideas will be greatly appriciated!!
    So you're sending water out at 160 and it's coming back at 140 but yet you're not heating up the room?

  3. #3
    Plumbing Contractor for 49 years johnjh2o1's Avatar
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    Sounds like you need more loops. Who figured the heat loss? The problem will become worse as the temperature drops.

    John

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    DIY Senior Member zl700's Avatar
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    Theres alot more to Radiant design but, I'm curious

    What size tubing, whats its spacing and did you use any plates?

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    DIY Junior Member alfpark's Avatar
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    I am using 1/2 inch tubing. no emision plates but foil double bubble stapled below runs in each bay. R13 under that. Fred Seton design 8 in. spacing. outside temps are averaging 30 day teens @ night. cant hold inside any better than 60-65. Just pruged system loops for air. Some but not signifcant.

  6. #6
    DIY Junior Member alfpark's Avatar
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    Quote Originally Posted by johnjh2o1 View Post
    Sounds like you need more loops. Who figured the heat loss? The problem will become worse as the temperature drops.

    John
    The temp has already dropped!! I have 2 runs per joist bay 8 inches appart dont even think I could fit more.

  7. #7
    Journeyman & Gas Fitter Doherty Plumbing's Avatar
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    Quote Originally Posted by alfpark View Post
    The temp has already dropped!! I have 2 runs per joist bay 8 inches appart dont even think I could fit more.
    Are you sure the thermostat is accurate and functioning properly??

  8. #8
    Retired Defense Industry Engineer jadnashua's Avatar
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    It doesn't take much air to block flow...you might want to purge the lines again...
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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