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snap/banging sound from PEX, doesn't keep up on cold nights upstairs

 When the temperature drops below about 4 F, one

zone won't maintain the 71 degree set point on thermostat. It will

drop to between 66 and 69.


  • patagoniaboarderpatagoniaboarder Member Posts: 9
    edited December 2013

  • kcoppkcopp Member Posts: 2,746
    wow... long post.

    Is there insulation? how much? Was there a  heatloss done? How long are the loops? What do you have for tubing? O2 barrier pex? What do you have for a boiler?
  • STEVEusaPASTEVEusaPA Member Posts: 1,452
    I'll take a crack at it....

    Am I correct to assume this is a new install? 2nd problem first.

    Heat not keeping up could be a result of many thing:

    1. You say you have a manifold upstairs. Are there flow meters on them? This would help diagnose flow problems.

    2. Do you have any diagrams of the design, loop lengths, heat load/loss, btu requirement, etc? Was carpet considered in the design?

    3. On the staple up zones, any aluminum transfer plates? This could be the bulk of your problem, necessitating ta need for a higher water temp, but not185 degrees.

    4. Bleeding needs to done properly, loop by loop, zone by zone.

    5. We're the joist bays w/staple up insulated properly?


    Although constant circulation could help, there's most likely an installation problem. Something is too tight. Installer should have got system up and running before drywall finished, if possible, to check for this problem.

    But overall, you paid a lot of money for your system, and rather then have the original installer trying to fix it with ideas that won't work, I would get a radiant consultant in there to go over everything, and make recommendations the original installer should correct.
  • patagoniaboarderpatagoniaboarder Member Posts: 9
    edited December 2013
    this is an existing install

    good insulation is verified
  • patagoniaboarderpatagoniaboarder Member Posts: 9
    edited December 2013

  • patagoniaboarderpatagoniaboarder Member Posts: 9
    and what about an outdoor reset?

    Is the plumber correct in telling me that he'd have to re-pipe a bunch of the stuff toward the boiler side of these pictures in order to do an outdoor reset? I don't quite understand why, as it seems like a different mixing valve could be used that is controlled by outdoor temp...and the mixing valve could simply let in more hot water in the cold winter days and less in the warmer spring/fall nights.
  • IronmanIronman Member Posts: 3,410
    edited January 2012
    The main issue...

    Is the lack of heat transfer plates.

    Adding outdoor reset can be accomplished by adding motorized or electronic valves and should not require major re-piping. This would probably reduce the majority of the noise, but would not increase the heat output in the areas that are lacking. However, your comfort may possibly be increased by the longer run times with a more balanced water temp. Maybe. No guaranty.

    Putting a larger boiler in will not do any good unless the present one is under-sized. Putting more logs on the wagon isn't gonna do any good if the mule (piping) can't carry the load now. You need to do a heat loss calc.

    I would recommend that you look elsewhere for professional help. The three "heat guys' that you've had are not.

    Mark Eatherton is in the Denver area and you won't find any better. Maybe he can help or direct you to someone who can. His foot prints are all over this site.
    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
  • patagoniaboarderpatagoniaboarder Member Posts: 9
    edited December 2013

    MANY THANKS again to everyone!
  • NRT_RobNRT_Rob Member Posts: 1,009

    1. yes, staple up systems can chew through pex over time. one of the many reasons this install method has fallen out of favor.

    2. it would be good to know why that valve is not working. can't tell from your pics what the issue might be. IF the valve really is clogged and not piped incorrectly then you could replace with a motorized valve, yes, but it would only serve the same areas that valve serves, which I would guess is slab only? at the very least you'll want 2 temps if you are doing slab radiant and naked staple up pipe, so you won't do this from one valve, most likely.

    3. if the reset curve is set properly you'll have close to constant circulation in the "lead zone" for each water temp nearly all the time.

    4. it's highly doubtful you're going to maintain 71 with plateless system. but it's possible.
    Rob Brown
    Designer for Rockport Mechanical
    in beautiful Rockport Maine.
  • patagoniaboarderpatagoniaboarder Member Posts: 9
    edited December 2013
    my two zones

    My two water temp zones are:

    (1) HOT water directly from boiler - ie. for hot water storage tank and baseboard zone.

    (2) less hot water that goes through a manual mixing valves - serves all other zones.
  • patagoniaboarderpatagoniaboarder Member Posts: 9
    edited December 2013
    thanks again

    I've gotten a lot of good advice from people so far, so thanks.
  • SWEISWEI Member Posts: 7,356
    mixing valve size

    In inches does not have to match the size of piping connected to it.  When properly sized for full authority (Cv) it can sometimes be a smaller nominal size.
  • NRT_RobNRT_Rob Member Posts: 1,009
    large tempering valves

    are very, very expensive. small ones like you have are very restrictive. lots of tradeoffs.

    slow acting zone valves will not help expansion noises appreciably. might make some difference.

    I have to admit I still can't follow your piping to tell if the 3 way valve is piped in properly. bit of a nest in there...
    Rob Brown
    Designer for Rockport Mechanical
    in beautiful Rockport Maine.
  • heat is now keeping up

    Problem was simple - one of my pumps was going out and wasn't circulating good enough. Now the heat keeps up!
  • GordanGordan Member Posts: 891

    This should have been apparent from the return temperature on that zone. Flow issues always show up as too high temperature drop through the branch. But you have to measure the branch return temp, not the system return temp, in order to detect this.
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