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  1. #1
    Join Date
    Dec 2011
    Location
    Hiram, Ohio
    Posts
    214

    seasonal air damper changes

    Hi again.. Goodman modulating furnace soon to be mated with a 2 stage HP, full communicating system.. In the winter, I open the ducts full in the basement and partly close some of them upstairs. In the summer, I open them all the way upstairs and close them in the basement. If my tech installs and sets me up in the spring / early summer when I have my ducts in "AC mode" should I be concerened in the fall when I switch the ducts to "heat mode" ? I suppose this somewhat depends on fan speeds set at the t-stat? the system can be programmed for fan speeds and profiles for propane heat, and AC... when this HP is installed will there be separate fan speeds/profile settings for propane heat, heat pump, and air conditioning? Thanks, Mike.

  2. #2
    Join Date
    Dec 2010
    Location
    The Quad-Cities area (midwest).
    Posts
    2,604
    You might want to consider zoning the home with automatic dampers. Let the dampers open/close automatically with a thermostat in each area (zone). With the variable-speed fan, the airflow will change as the dampers open or close to maintain the proper amount of air needed.

  3. #3
    Join Date
    May 2008
    Location
    Missouri
    Posts
    3,424
    Are we to assume most of the ductwork is covered and non-accessible? So difficult to actually zone?

  4. #4
    Join Date
    Dec 2011
    Location
    Hiram, Ohio
    Posts
    214
    There is one main trunk line running along the ceiling in the basement, with individual 6" round runs for each register in the entire house. 16 runs not counting the three outlets in the main trunk for the basement. All runs are labeled, which makes it simple for me to manually "zone" it depending on the season. All runs have butterfly valves. The basement is not finished, but it is very clean, dry, and painted.

  5. #5
    Join Date
    Dec 2010
    Location
    The Quad-Cities area (midwest).
    Posts
    2,604
    Quote Originally Posted by troyport View Post
    There is one main trunk line running along the ceiling in the basement, with individual 6" round runs for each register in the entire house. 16 runs not counting the three outlets in the main trunk for the basement. All runs are labeled, which makes it simple for me to manually "zone" it depending on the season. All runs have butterfly valves. The basement is not finished, but it is very clean, dry, and painted.
    Is your home a ranch or a two story? What size is the heat pump going to be? What size is the A/C now? This will let us know how many supplies need to be left open.

  6. #6
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    THe heat pump normally rusn hte same blwoer speecds as AC since it's has hte same airflwo requirements. The furnace will likely be lower airflow.

    However how mcuh airflow only matter if your ductwork is too small. Adjusting a damper on a main trunk has a proportional effect. Meaning you are diverting a percentage of the airflow and doing it by creating resistance in the duct, thereby increasing the pressure in the plnum and forcing more air the less restricted duct.

    The fan speed are porbably only when running the fan seperately, not when runnign the equipment. Some system do allow some airlfow reductions for comfort and dehumidification, but not by more than 20-30%.


    What equipment brand and model and what size were installed. Tell us a little more about the house. 2 story homes almost always need to be zoned manually or automatiacally in a 4 season climate. Properly sized equipment will reduce the differture difference between floors and make balancing easier. You cannot size equipment based on square footage, especially 2 story homes, since they will have lower heat loss and gain than the same size single story home.

  7. #7
    Join Date
    Dec 2011
    Location
    Hiram, Ohio
    Posts
    214
    2100 square foot colonial built in 1990, typical construction grade, nothing fancy. load calcs taken at time of furnace purchase made it a crapshoot between a 60K and a 80K furnace. I have the Goodman modulating 80K, and in hindsight should have gotten the 60K. But I like using setbacks during the winter. The HP is going to be a 2-stage, 3 ton. The load calcs suggested a 2.5 ton, but at least once every summer my current 3 ton AC would run non-stop, and since the new one is going to be a 2-stage I am going with the 3 ton. FWIW, with the old AC and new furnace, I set the AC blower speeds for the correct CFM from the charts for 3 ton, and had a 15 - 20 degree temp drop across the evap, which is how it always was, so it seemed pretty good.

  8. #8
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    A better way to set blower speeds is t measure temp rise in heating with the furnace to get a baseline CFM, then pull out hte installation manaul and look-up the blower data to find the correct speed for the AC. A 15-20F temp drop assumes the unit is charged correctly, and depends on humidify level and indoor and outdoor tmerpatures. Too many vairables. But 20F is pretty safe and too much air flow won;t hurt it, but it will could be a little noisier amnd use slightly more energy.

    Of course with VS, that's not an issue.

    I'd use the normal blower speed and utilize dehumidify on demand features ot slow the blwoer as needed. That way it you get ht most effceincy and capacity when you have long run times, but under low load conditions, in cool weather, it dehumidifier a little better.

    For hte heat pump, I think you can set a tmerpature when it will lower the CFM below a certain outdoor temp for a higher heat rise. This drop effceincy a little, but makes it more comfortable. For the constant fan. I personally keep mine in Auto most of the time to save energy and get more out of my furnace filter, except nighttime, then I run it on low, which on carrier Infinity is 50% of the highest equipment speed.

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