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Cool room

KTS Member Posts: 4
I have radiant heat and my first floor is on one zone. My living room is 5 degrees cooler than the rest of the house, how can I correct this issue?


  • Gordan
    Gordan Member Posts: 891
    edited October 2010
    What kind of radiant?

    Radiant floors? If so, what's the floor covering situation in the various rooms?

    How long has the system been in operation? When did the problem start? Has anything changed between then and now?

    Any details you can provide about the rooms and the heating system will help us help you.
  • KTS
    KTS Member Posts: 4
    Re: Radiant heat

    I have in floor radiant heat and a hot water system with a Buderus GB 142 gas boiler. The system is three years old and I have been having this issue since day one. The system seems to have trouble keeping the house warm at cold temps (0-10). However the worst of the problem seems to be in the living room where it is always colder than the rest of the house. The flooring is the same on the entire first floor, engineered hardwood.
  • Gordan
    Gordan Member Posts: 891
    edited October 2010
    More details needed

    Can you provide a sketch of your downstairs with relative room sizes, door openings and whether they're typically open or closed? Do you have rugs or large skirted upholstered furniture or anything else that would block the output of the radiant floor? Are there any drawings of the tubing layout that the contractor provided? What kind of radiant floor is it - tubing embedded in gypcrete or in a concrete slab? Staple-up? With or without plates? Are there manifolds? How many loops in the first floor zone? Do the manifolds have balancing valves? What are the loop lengths? Does the boiler run on outdoor reset? What's the reset curve look like?

    Some possibilities for what could be going wrong:

    - too much obstruction on top of the floor

    - flow is not balanced properly across the loops (if you know where, on the manifold, the takeoffs for your living room are located, you could just feel it and note any perceptible differences between that loop and other loops)

    - there is a problem with air binding, kinked tube, or other obstruction, and there's no flow to that loop at all - the only heat in the living room comes from other rooms

    - all the rooms are on the same loop (!) and the living room is at the end of it (that would be a near worst-case scenario)

    Etc. If you can snap some pictures of your mechanicals and post them, it may help with the diagnosis. Did you try to contact the installer?
  • CMadatMe
    CMadatMe Member Posts: 3,085
    Are we Plateless

    Did you use plates? Is the tubing suspended with clips? Is the tubing stapled to the bottom of the sub floor? If no plates are we sure there was a 2" air gap left between the insulation and the tubing?

    How is the radiant controlled? Thermostatic mixing, variable speed pump? What water is the system set up to run at design temp (coldest day)?
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • tim smith
    tim smith Member Posts: 2,397
    edited October 2010
    Other questions

    Is this a old house, does the living room have old single paine windows and the rest have updated ones. Were other areas insulated during a remodel but living room untouched. Do you have an area carpet in living room covering good portion of floor. How is the infiltration on windows/doors. Is the living room loop over 350ft or so. All will have an effect on how well this area heats vs others. As others stated, did they use plates with under floor tubing. etc etc etc. Inquiring minds want to know.

     Maybe they used one 1000ft roll and just kept pulling and pulling:)
  • KTS
    KTS Member Posts: 4

    It is a new home built in 2007. All of the windows are new quality windows. The radiant is in the concrete floor and the house was built on a frost wall and slab with no basement due to a wet area. The water is from a private drilled well. As far as the length of the loop, I am not sure. The floor and walls were insulated before the concrete was poured. The water is set at 170 degrees I believe as far as the mixing I am not sure. I believe there were two loops run, one for the living room and one for the kitchen dining and half bath. I am sorry I can't answer all questions as I am not that knowledgeable about the system. I will try to snap a picture of the system later today and post it. Thanks for all of the help.
  • Gordan
    Gordan Member Posts: 891
    Please be sure to take pictures of the manifolds

    If there are valves on each loop, we may be able to suggest some troubleshooting steps.
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    I hate when that happens (to me).

    My house has in slab radiant downstairs. 5 1/2-inch tubes enter the slab apaced about 2" apart. One one-inch tube returns. There are 5 rooms there. There was a funny manifold hooked to those 5 tubes, but the slotted shafts at the top turned forever and made no difference, so I had it replaced. Contractor put in 5 ball valves.

    1.) I have no idea if there was insulation under the slab.

    2.) I have no idea if there is insulation around the edge of the slab.

    3.) I have no idea as to the spacing of the tubes.

    4.) I had no idea which ball valve went to which room.

    I turned on all the ball valves full on to start with.

    I assumed that no tubes crossed one another. No idea if this assumption is correct.

    I drew a layout that might be true.

    I waited until it got cold and turned off one of the ball valves and waited many hours to see if one room's floor cooled off. Took quite a while. Rinse and repeat. Determined my initial layout was wrong.

    Came up with a second layout. It was wrong too.

    Now have a third layout that I imagine is correct.

    Three ball valves are full on. My bedroom is slightly throttled down. My computer room is almost off (can hear water rushing through that ball valve). One computer has 650 Watt (output) 70% efficient power supply, and the other one is more normal. That is a lot of heat.

    Had contractor zone upstairs (baseboard) separately from downstairs. Upstairs was always cold since system operated at a temperature more suitable for in-floor radiant. Now I put hotter water upstairs than downstairs. Contractor used Taco 007s for all circulators. Probably correct for downstairs, but I do not know because I do not know the lengths of the 5 loops; unlikely they are the same. Upstairs loop has about 65 feet of 1/2 inch tubing, 25 feet of 3/4 inch tubing, and 28 feet of 3/4-inch Slant/Fin. I infer that the 007 is too big from the fact that the temperature drop is only a few degrees, once it stabilizes. I.e., when it starts running it is more because of the cold water in the loop, but when the return water warms up it is almost the same as the supply.

    I do no mixing because the reset for upstairs zone and downstairs zone are different, so the water temperature supplied is kind-of independent. It is a small Cape Cod and the upstairs zone requires very little heat. (6500 BTU/hr when it is 0F outside. Design day is 14F around here.)

    I wish they had to supply a layout of the tubing in the slab. It would be easy if they prepared one before the concrete was poured.
  • Brad White
    Brad White Member Posts: 2,393
    When all of the other variables are fixed

    meaning circuit length, spacing, depth, insulation... then temperature is all you have to work with.

    A supply temperature of 170 was mentioned but is that at the boiler or out to the circuit? For concrete, even with carpet on it, that is too high, if indeed that is what you are sending out to the floor.

    As others have mentioned, once you have the floor areas, tubing diameter and number of circuits (we can only guess at the lengths), we can get a better picture.

    One thing I would do is look for a local energy auditor who uses an infrared camera. This can reveal the tubing pattern, perimeter losses, hot and cold spots, not only in your current problem room, but for comparison, the rooms that now work. Fire up the floors and take a peak through IR.
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"

    -Ernie White, my Dad
  • tim smith
    tim smith Member Posts: 2,397
    RE: living room radiant problems

    Maybe it is as simple as a bad telestat?? Or could be a kinked loop. Will be intellesting to find out. Tim
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