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  1. #1
    Join Date
    Jan 2013
    Posts
    8

    Humidification difficulty

    Hello,

    My house was built early last year, and this is the first winter I'm in the house. The house has a RUUD RGFG 75K BTU gas furnace and matched A/C. I also have a communicating thermostat (501), which apparently can't control humidifcation function (but can control dehumidification). I also have a bypass humidifier on the furnace, with a manual control.

    The trouble I'm having is that the humidifier doesn't seem to help much -- when it runs anytime the system runs it increases humidity levels 2-3% (from 22% RH to 25% RH at 25 deg F outside temp, and 70 deg indoor temp). The furnace is modulating with a variable speed motor, and while it tends to run for longish periods of time, it tends to run at a comfortable 400 CFM (low noise), at 40-50% capacity.

    My hunch is that the airflow is too low for bypass humidifier to do much, and thus I'm just wasting water. Should I replace it with a powered humidifier? Do you think it would help resolve the problem?

    The house is 3600 sq. ft, and has a second furnace in the attic covering the second floor. Similar problem there, though humidity is more reasonable at 30-33% RH under the same conditions.

    Thanks!

  2. #2
    Join Date
    Sep 2009
    Location
    Arnold mo
    Posts
    3,955
    How many people living in the home? Just because a house is newly built does not mean it does not have major air leakage. Air leakage in winter allows cold dry air to push its way into the lower leaks in the home, which then pushes the warmer moisture air out of the upper area leaks.

    Before looking into the humidifier, I would have your home tested for air leakage.
    An answer without a question is meaningless.
    Information without understanding is useless.
    You can lead a horse to water............
    http://www.mohomeenergyaudits.com

  3. #3
    Join Date
    Jan 2013
    Posts
    8
    I'm sure air leakage is a problem in a number of spots, and I intend to do an energy audit, but it's unlikely I'm going to be spending a lot of money at this point on a fix. A fix to humidifier option seems pretty inexpensive and much quicker relative to other options. The house does have rim joists spray foamed, insulated basement walls (R-12), foam sealing around windows and doors, as well as wall outlets and switches on exterior walls. Windows are energy star rated andersen 400 series DH. However, the house wasn't built to energy star standards, so I'm sure there are areas for improvement.

    Still would love to hear thoughts on the humidification question.

  4. #4
    Join Date
    Sep 2009
    Location
    Arnold mo
    Posts
    3,955
    You just need to figure out whether fixing the air leaks now will be the least expensive option, or whether paying constantly higher heating & cooling bills will end up costing you more.
    An answer without a question is meaningless.
    Information without understanding is useless.
    You can lead a horse to water............
    http://www.mohomeenergyaudits.com

  5. #5
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,315
    You could have excessive duct leakage (assuming ducts are in attic) that is counteracting a lot of the work your humidifier is doing. I would put more focus on a duct leakage test first off since the house itself is pretty new and hopefully tight. Fixing the ducts will improve a lot of things in addition to humidity control in winter.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  6. #6
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,060
    A bypass humidifier does not work well on a modulating furnace. The pressure differential between the supply and return, low velocity and lower temperatures at the lower en prevent enough evaporation to do much.

  7. #7
    Join Date
    Dec 2010
    Location
    The Quad-Cities area (midwest).
    Posts
    2,626
    I would make sure that water is flowing thru the humidifier. Make sure the humidifier was installed level. Also make sure the damper is open. I assume you can hear the solenoid open and close. Normally we find new home have an excess of humidity from the new construction materials.

  8. #8
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,333
    Quote Originally Posted by George2 View Post
    I would make sure that water is flowing thru the humidifier. Make sure the humidifier was installed level. Also make sure the damper is open. I assume you can hear the solenoid open and close. Normally we find new home have an excess of humidity from the new construction materials.
    I fixed a bypass humidifier by install a 6" duct fan in the bypass duct, +200 cfm. I had the windows dripping in two days. You do not get enough air flow from a by pass. Even the standard fan does not have enough. +200 cfm works much better.
    Regards TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  9. #9
    Join Date
    Jan 2013
    Posts
    8
    Thanks for the suggestions. The issue is with the furnace in the basement, so duct leakage is probably not the major issue -- the basement is insulated and stays at 68 deg. F, and all ducts are sealed up with mastic. The humidifer is level, and water is flowing through it just fine.

    Sounds like the problem is air flow is the root of the problem. Short of the 6" fan in the bypass duct (interesting idea), would a switch over to a power humidifier be a reasonable fix?

    The overall air sealing is a separate issue, and one I intend to address as well -- I'm having a blower test done after the holidays to see where I stand at the moment. A quick walk through with a thermal imaging camera I borrowed from a friend found a couple of spots, which have been addressed, but everything else looked not too terrible. Fixing the drafts I did find, made no difference to the humidity issue though.

  10. #10
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,874
    What brand and model number humidifier do you have.
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    How many times must one fix something before it is fixed?

  11. #11
    Join Date
    Jan 2013
    Posts
    8
    Not 100% sure, it's a York, but probably relabeled aprilaire 600.

  12. #12
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,874
    Quote Originally Posted by ddr View Post
    Not 100% sure, it's a York, but probably relabeled aprilaire 600.
    They put a York label humidifier on a new Rheem furnace. LOL

    Is it connected to the cold or hot water line.
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  13. #13
    Join Date
    Jan 2013
    Posts
    8
    It's connected to the cold line.

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