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Radiant Heat trouble

as a new topic! ;)

Comments

  • Matt_66
    Matt_66 Member Posts: 15
    Radiant Heat trouble

    I had radiant heat installed in my kitchen and just noticed that half the floor heats up very fast and the other half takes a very long time. The water coming through the PEX tubing is hot going in but the return is just luke earm. Is this normal or is there a problem with the heating?
  • EMB
    EMB Member Posts: 37
    Need more info

    Sq. footage, size of tubing, length of end runs, size of circulator, design flow rate, actual flow rate etc.

  • Any way,,,

    you can trace and inspect the cold side loop(s) for a kink? Unless the loop is way too long which goes back to what EMB said, more info needed.
  • Timco
    Timco Member Posts: 3,026


    Could be that there is one big loop, and the hottest water goes in one side and is cool by the time it gets to the other side but if one side is really hot and one not, could be unbalanced flow, where two loops are moved by the same circ and one is being favored, and needs to be restricted by a circuit setter type devise, or as mentioned, a loop may have a kink and the other gets the flow...

    Tim
    Just a guy running some pipes.
  • True, could be

    one or more balancing valves closed too much at the manifold. Hopefully it's that simple.
  • Matt_66
    Matt_66 Member Posts: 15
    Radiant Heat trouble

    The room is about 280sq feet. It is one run of PEX tubing. I believe it is 1/2 inch tubing. It does run hot into one side and comes out cool on the other. I do not know the size of the circulator.
  • tim smith
    tim smith Member Posts: 2,397
    280 sft, one loop?, could be 500 + ft loop!!!!!

    If 2 runs per joist bay, this sounds like wayyy too long of a loop. Would definately cool down alot by the time it returned. Something sounds fishy. Tim
  • Matt_66
    Matt_66 Member Posts: 15
    Any fix?

    The room is 280 sq ft. With the cabinets and appliances, the PEX is probably only under about 180 sq ft. Everything is already finished is there any way to remedy the problem?
  • scott markle_2
    scott markle_2 Member Posts: 611


    Does it effect your comfort? Well modulated radiant in a decent envelope often makes "warm floors" somewhat of a misnomer. The best radiant systems deliver heat at variable temperature, not in the on/off fashion of convective heating systems.

    Maybe you have a setpiont mixing valve and a room thermostat that cycles the circulator. If this is so you might try turning the setpiont down, this will keep the circulator on more of the time, evening things out.
  • Uh oh,,,

    even at 180sq ft times two runs per joist space you are looking at ~ 360 ft or so of 1/2" tube. Last I recall 200 ft of 1/2' was recommended max length. If this is the case the best repair is to find a way to split that single loop into two loops somehow. Easier if it was strapped up underneath, not so easy if it's above imbedded in the floor. OR if you could find a way to reverse the flow back and forth regularly, you may squeak your way out of this one. I have seen devices that will do that but not for this particular application. And didn't I find it in the stuff I got at the NYC expo: try Water Technology of Pensacola, Inc. 800-282-7978 www.atbsystems.com [email protected] The reversing device is not intended to be used in this manner but it MAY work for you. Just a shot in the dark I'm afraid. Whoever did the install should be contacted and made to address the problem themselves though. Good luck
  • Looks like,,,

    the smallest they go is 4" pipe but I KNOW they had a smaller display one at the show. Worth a try if it's your only choice. Or maybe it can be rigged to reverse another way like with zone vales or something. Just a thought.
  • jp_2
    jp_2 Member Posts: 1,935
    how does it function?

    does the pump run all the time or is it connected to a thermostat?

    a reversing valve is a common fix for this type of problem.

    re-post and ask "Hot Rod or ME, reverse valve, floor tubing too long" I believe they have done this type of 'fix' before.

  • I'll be,,,

    intersted in that answer myself.
  • Matt_66
    Matt_66 Member Posts: 15
    Reverse valve for Raciant heat - Tubing too long

    Can anyone help with the workings of a reverse valve for Radiant heat? My radian heat is connected to a thermostat. I can turn it up to 82 degrees and it takes about 4 or 5 hours for the floor to get hot. the one side is very hot and the other is still lukewarm but a lot warmer than it has been.
  • steveex
    steveex Member Posts: 95


    You can do constant circ. will help with some swings and time.
  • scott markle_2
    scott markle_2 Member Posts: 611
    constant circ.

    I also suspect constant circ. would probably fix it.

    Constant circulation requires using water only as warm as required, this is regarded as the best way to minimize the thermal inertia inherent to radiant systems.

    Any temperature gauges? what are you using for a supply temp? PDI thermostat?

    I think a mixing or injection station with a well calibrated reset curve would be cheaper than the reversing setup and would probably do the trick.

    What does the installer say?

  • EMB
    EMB Member Posts: 37
    Sorry all

    Been away from the site for a couple of days.

    Matt, do you know the length of the loop? Also, what is the make and model of the pump. We need to figure out why you have such a high delta T across that loop. Also, I may have missed this somewhere in the post, but what are we dealing with; staple up, gypcrete etc?
  • jp_2
    jp_2 Member Posts: 1,935
    quick test

    first what is the water temp of the floor zone?

    set the supply floor temp down to 90F, set the tstat at 85F, let the room 'run' all day. does the floor temp even out?

    this can help decide if constant circulation can solve the problem or not.

    how does the tubing attach to the floor?
  • Matt_66
    Matt_66 Member Posts: 15
    Radiant Heat trouble

    this is a reply for all. Again, thanks for the help.

    The tubing is 1/2" and is in the concrete subfloor with the tile on top. It is one loop and the pump is a TACO 007. The room is 260 sq ft but with cabinets/appliances/closet/bench seat the actual tile floor the radiant is under is approx. 160 sqft. It is controlled by thermostat and when i ran it at 82 degrees for about 4 hours the floor evens out somewhat. I would like to get it so it is even at a lower temp and much quicker.
  • Matt_66
    Matt_66 Member Posts: 15
    const cir

    The temp at the furnace for the floor is set at 120 degrees. Like I said, when I set the thermostat at 82 degrees (that is as high as it goes) it evens out after 4 or 5 hours. tubing is embedded in subfloor concrete. Is const. cir require anything additional or is it just keeping the temperature at one setting?
  • jp_2
    jp_2 Member Posts: 1,935
    theres most of the problem

    120F is too high for concrete.

    i run a tile on top of gypcrete floor at 90-95F, no controls, runs 24/7 in winter.

    i'd guess since part of the floor is real warm, the other part then feels too cool but could be at reasonable temp.

    Is that concrete well insulated bottom and sides?

    I think if you lower the water temperature, you'll find it runs almost all the time still using the thermostat.

    give it a try.
  • Matt_66
    Matt_66 Member Posts: 15
    const cir

    why is the 120F too high? so if I lower the water temp to 90F what should the thermostat be set at to keep it running.

    And yes, the floor is insulated underneath in the crawlspace and on the sides.
  • jp_2
    jp_2 Member Posts: 1,935
    remote trouble shooting

    from what I see from your posts:

    the hot water is over heating the floor in the first half of the loop, this small 'hot/warm' area shuts down the tstat, room seems warm but other part of floor "seems" cold.

    too much temperature difference at first causes big temp difference across the floor, lots of heat transfer at first.. so if you lower the loop temp, the temp dfference at first will be less and thus the temperature will be 'more' consistant across the whole room, floor temps will be more even.

    walk around and measure the floor temps,

    its still possible you loops is too long, but sounds like we have no idea how long that is?

    how is the rest of the house heated?
  • Matt_66
    Matt_66 Member Posts: 15
    trouble shooting

    I'll try lowering the loop temp this weekend and see if that helps. I can also measure to see how long the loop actually is. I know how it was set up before the mudjob was put on top.
    The rest of the house is heated with radiators.

    Also, the thermostat in the room is on the side that heats up first. So maybe it is shuting off before the other side heats up.

    So you recommend setting the loop temperature at 90-95F and keeping the thermostat at a constant setting in order to maintain an even effect?
  • jp_2
    jp_2 Member Posts: 1,935
    just a suggestion

    for a starting point. you might find 80F works or 110F works.

    or you are going to find that the boiler doesn;t like just supplying the floor circuit?

  • Matt_66
    Matt_66 Member Posts: 15
    thanks

    Thaks for the help. I'll let you know what happens this weekend
  • Techman
    Techman Member Posts: 2,144
    Time

    What would be a normal ammount of time for this floor to get up to a "stabilized " condition?Air Conditioning can take several hours to stabilize an area.
  • A day or two...

    ya gots to give it time! ;)
  • chris_93
    chris_93 Member Posts: 84
    pipe length

    depending on the brand look at the supply and return lines, there should be writing indicating brand, o2 barrier, and lengths every 3' feet i believe. Subtract the 2 numbers and that is the loop length.
  • steveex
    steveex Member Posts: 95


    If we all keep giving him advice it will be spring soon, and time for ac, if you have a well for a sprinker system pipe it in the circut, for fun.
This discussion has been closed.