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Thread: Fan settings

  1. #1
    Join Date
    Dec 2010
    Posts
    71

    Fan settings

    I have a new Bryant evolution HVAC system installed which is tied to a Bryant evolution thermostat. The installer suggested that the fan setting be left on Low. His rationale was that the fan running on low at all times would add to the circulation and comfort in the home. He mentioned that since the blower is an infinte speed blower it would adjust as needed when the heat or AC came on, so not always running on low. He said they recommend the upstairs level (second floor) system to be on Auto and the main level on Low. Said that running the fan all year on low is like $40 per year so not significant.

    Does this make sense?

    Thanks

  2. #2
    Join Date
    Sep 2006
    Location
    Montana
    Posts
    983
    Constant fan operation will accomplish several things. Better overall comfort, constant air filtration(= cleaner indoor air) and more even and consistent temp. throughout the house. I run my blower continuously, 24/7. This may not work for everybody, depending on where you live and what humidity levels you're dealing with. For me, it works well.

  3. #3
    Join Date
    Jan 2002
    Location
    Ft.Worth,Tx
    Posts
    4,584
    Quote Originally Posted by bigkutta View Post
    I have a new Bryant evolution HVAC system installed which is tied to a Bryant evolution thermostat. The installer suggested that the fan setting be left on Low. His rationale was that the fan running on low at all times would add to the circulation and comfort in the home. He mentioned that since the blower is an infinte speed blower it would adjust as needed when the heat or AC came on, so not always running on low. He said they recommend the upstairs level (second floor) system to be on Auto and the main level on Low. Said that running the fan all year on low is like $40 per year so not significant.

    Does this make sense?

    Thanks
    I would follow what the set-up for that unit states,low fan speed would help with circulation, but if house has more than 4 * set differential , could add some humidity to the home.
    "Everyday above ground, is a good day".
    "But everyday that you have made a difference in someones life, may insure you stay above ground a little longer".<aircooled>

  4. #4
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,373
    All of that your tech says is true. Add the fact that with fan "on", the coil/ducts will be drier and less prone to "wet sock syndrome" odor problem. The negative point is that any moisture on the cooling coil is re-evaporated back into the home. The moisture on most a/c coils is +1lb. of moisture per ton of capacity. When an a/c operates at 75^F, 50%RH, with a 45-50^F coil, it takes 30 minutes for most dry coils to get saturated enough to start dripping to the drain (+1 lb/ton). A lb. of moisture humidifies 900 sqft of home +10%RH. It takes 30-40 mins. for the moisture evaporate from the coil with the fan on low. A short cycling a/c with fan "on" does not remove much moisture.
    As a home becomes higher %RH, the a/c will remove more moisture which decreases the problem somewhat.
    I operate with fan "on" but use t-stat setup to increase the length of the cooling to remove more moisture. By raising the day/afternoon temp to 80^F, then the t-stat lowers to 75^F at 5:00 PM. This get me one hour of continuous cooling on a hot day. My basement helps cool my house which also supports the fan "on" mode.
    The bulk of my moisture removal is from the whole house ventilating dehumidifier plus the 1-2 hour afternoon/evening cycle. 30-40 lbs. of mositure per day is typical with +65^F outside dew points.
    Without the basement, I suggest fan "auto" unless you are have the "wet sock syndrome" odor problem. During wet weather, you will need a whole house dehumidifier for <50%RH. Adequate fresh ventilation on moisture from the occupants requires the 30-50 lbs. of moisture removal with +65^F outside dew points. This gets real indoor comfort and control over mold/dust mites in the home and ducts.
    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"

  5. #5
    Join Date
    Feb 2007
    Posts
    999

    Question for Teddy Bear

    Regarding your statement: "My basement helps cool my house which also supports the fan "on" mode.", do you have a finished basement with supplies and return(s)? I ask this based on (my) current heat load where the cool 1st floor (stat location) prevents the a/c from coming on, and allows the 2nd floor to rise in temperature.

    If my assumption about your situation is correct, then your fan on is pumping cooler basement air throughout the house.

    Today, I tried an experiment. This morning, I switched the fan to 'on'. Based on similar OD temps the last 2 days, I seem to be about 3 - 4 degrees cooler upstairs.

    Once, I tried switching the fan back on at the conclusion of a call for cooling. It immediately became muggy in the house. I seem to recall the constant speed fan was set on high. Would running it on low (which I have it set to now as my winter setting) lessen the possibility of 'rehumidifying' the house?

    Thanks for your input.

  6. #6
    Join Date
    Dec 2010
    Posts
    71
    good points. The new system serves the basement (Intake and supply) and main level, and the basement is very cool, so I guess running the fan at all times may lower the main level temp and lower the ac use.

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