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  1. #1
    Join Date
    May 2005
    Location
    Chicago suburbs
    Posts
    11
    In May I had a new Carrier Infinity system installed:

    Furnace A58MVP100-F
    AC 2 SPD 38 TDB0483
    Aerosealed the ducts

    in my 2,200 sq ft mid-1960's 3 bedroom ranch home. The home is well shaded by old growth trees, located in the Chicago suburbs. Attic has R38 insulation. Ducts are insulated sheet metal, size 16x20 with static pressure of .43 after Aerosealing Windows are old 1960's Anderson double payne WindowWalls. One skylight and 2 solar tubes.

    The problem is high humidity. The Infinity controller continually shows 60%-65% humidity even though it perfectly maintains 72F no matter the outdoor temp. To keep humidity around 50% I run a 50 pint portable dehumifier in the house that collects about 1.5 to 2 gallons of water every 24 hours.

    The Infinity system is excellent other than this. It is nice and quiet, and vary rarely runs on high. I am hoping for better humidity control, if possible.

    Is a whole-house dehumifier the answer? Is it the shady trees that don't let the system run long enough?

    For whatever its worth, I believe the installer said he set the AC for "efficiency"

  2. #2
    Join Date
    Jul 2005
    Location
    south
    Posts
    588
    need to get install/program manual and check all program parameters very carefully. configured inproperly.

  3. #3
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,914
    Change it over to "comfort", and you will get better humidity control.

    That is about the extent of my knowledge of the Infinity controls, so don't ask me for more details.
    If more government is the answer, then it's a really stupid question.

  4. #4
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    There are options,as mentioned ,comfort setting lowers cfm to 350 per ton,cool to dehumidify ,will run the system 3 cooler to dehumidify,I don't think I'd use that function when stting it at 72.

    In low speed it's only 2 tons,so it should be able to run a lot and dehumidify bette then what you are getting.

    What is your humidity set point?

  5. #5
    Join Date
    May 2005
    Location
    toronto canada
    Posts
    25
    Unfamiliar with carrier controls but i would assume that the system has a setting for dehumidify and would be curiuos to know what this is set at.Also usually this setting will allow unit to run at lower air volume even though the temperature in the house is satisfied to bring the humidity down.Other than that it sounds like it was not programmed propperly.

  6. #6
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,260
    With +90^F outside, air tight ducts, and a cold coil, you should be able to maintain 50%RH without a dehumidifier. Shade and insulation cuts cooling load which decreases sensible load and decreases the a/c's dehumidification. Do you have a crawlspace with exposed earth or open outside vents? They are a big humidity load. With rain and low/no cooling load expect to need 70-80 pints (6-7 gal./day)of dehumidification to maintain <50%RH. Just fixed a house in KY with the same a/c/problem with whole house dehumidifier. They tried lowering the t-stat to cool the home dry. Picked up musty odor throughout the home after several months of 68^F with 55-65%RH. Used 100 pint dehumidifier to get to <50%RH. Odors went away. Tobe fair, we are dehumidifier mfg and are selling thousands in this damp weather. Your a/c guy can do this.

  7. #7
    Join Date
    Mar 2004
    Posts
    1,042
    This sounds oversized to me, given the heavy shade.

    Two speed equipment is somewhat more tolerant of oversizing than single speed, but there are definitely limits. If the system is still running mostly on low while keeping the house at 72 in this heat wave, that would be a confirmation of my hunch.

    Leave the fan in Auto until cooling season is over; continuous fan operation will definitely hurt its ability to dehumidify. If you have been using Auto already, have them come back and switch the AC mode from Efficiency to Comfort. That will help a bit with dehumidification.

    The system will not overcool by three degrees from a thermostat setpoint of 72. When your cooling setpoints get this low, the extent to which it will overcool tapers off to zero. So I'd say to go ahead and use the Dehumidify function -it's on the Advanced screen related to cooling. It's probably already on, though. On the same screen, make sure the cooling setpoint for humidity is cranked down to the minimum, or close to it.

  8. #8
    Join Date
    Mar 2005
    Posts
    997
    What is wrong with using your 50 pint dehumidifier?

  9. #9
    Join Date
    Jul 2004
    Posts
    253
    Try measuring the RH with a quality instrument and adjust User Interface RH reading to match an insturment - go under service menues. The RH sensor may be mis-calibrated.

    Originally posted by jthatcher
    In May I had a new Carrier Infinity system installed:

    Furnace A58MVP100-F
    AC 2 SPD 38 TDB0483
    Aerosealed the ducts

    in my 2,200 sq ft mid-1960's 3 bedroom ranch home. The home is well shaded by old growth trees, located in the Chicago suburbs. Attic has R38 insulation. Ducts are insulated sheet metal, size 16x20 with static pressure of .43 after Aerosealing Windows are old 1960's Anderson double payne WindowWalls. One skylight and 2 solar tubes.

    The problem is high humidity. The Infinity controller continually shows 60%-65% humidity even though it perfectly maintains 72F no matter the outdoor temp. To keep humidity around 50% I run a 50 pint portable dehumifier in the house that collects about 1.5 to 2 gallons of water every 24 hours.

    The Infinity system is excellent other than this. It is nice and quiet, and vary rarely runs on high. I am hoping for better humidity control, if possible.

    Is a whole-house dehumifier the answer? Is it the shady trees that don't let the system run long enough?

    For whatever its worth, I believe the installer said he set the AC for "efficiency"

  10. #10
    Join Date
    Jul 2005
    Posts
    14
    I'm just a homeowner, but wow your system seems way oversized to me. I live in Toronto, Ontario so our climates are pretty similar. My house is about 18 years old, with many oversized windows. It is about 2600 sq feet. My Carrier MVP furnace is 80,000 BTU. Last winter, the only times it went into high, were in the morning after having set back the temp for nighttime.

    As far as the a/c - we have the Infinity 3 ton. It has maintained set temps of 73 or 74 with outdoor temps in excess of mid 90's. My only complaint, is the RH goes too low for my comfort. So we simply increase set temp to 75 or 76 on the really hot days.

  11. #11
    Join Date
    Nov 2002
    Posts
    94
    Originally posted by teddy bear
    With +90^F outside, air tight ducts, and a cold coil, you should be able to maintain 50%RH without a dehumidifier. Do you have a crawlspace with exposed earth or open outside vents? They are a big humidity load.
    Teddy Bear,

    I live in Richmond & have a crawl space (over a brick house) w/vents that I open in the summer time. It also has some plastic down but some spaces of earth are showing.

    Should I close vents? I was always told open vents in summer & close in winter.

  12. #12
    Join Date
    May 2005
    Location
    Chicago suburbs
    Posts
    11
    Thank you for your help!

    In answer to the questions posed:

    There is a large, 4 foot high crawl space below the home. It has cemented walls and floors, with the walls insulated with foam insulation panels. I run a portable dehumifier in the crawl there set at 50%, draining automatically to the sump pump drain with a hose. I suspect that moisture from the ground seeps through anyway, even through the old owner said the cement was "treated." Left alone, the crawlspace tends to remain significantly cooler but higher in humidity than the living space.

    On the Infinity, I've set the dehumidity percentage to 46%, the lowest setting.

    I want to keep living space humidity down to due my allergies. I am not allergic to mold (thank goodness), but am quite sensitive to dust mites and they love 50%+ environments.

    The portable dehumifier works, but is noisy and a bother to empty every day, particularly considering the low noise and automation of the Infinity. I want to make sure I am achieving as much dehumidification I can realistically getbefore considering the expense of a whole house dehumifier.


  13. #13
    Join Date
    May 2005
    Location
    Chicago suburbs
    Posts
    11
    Thank you for your help!

    In answer to the questions posed:

    There is a large, 4 foot high crawl space below the home. It has cemented walls and floors, with the walls insulated with foam insulation panels. The vents are closed. I run a portable dehumifier in the crawl set at 50%, draining automatically to the sump pump drain with a hose. I suspect that moisture from the ground must seep through even through the old owner said the cement was "treated." Left alone, the crawlspace tends to remain significantly cooler but higher in humidity than the living space. There are no obvious slope or drainage problems along the house.

    On the Infinity, I've set the dehumidity percentage to 46%, the lowest setting.

    I want to keep living space humidity down to due my allergies. I am not allergic to mold (thank goodness), but am quite sensitive to dust mites and they love 50%+ environments.

    The portable dehumifier works, but is noisy and a bother to empty every day, particularly considering the low noise and automation of the Infinity. I want to make sure I am achieving as much dehumidification I can realistically get before considering the expense of a whole house dehumifier.


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