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  1. #1

    Confused AC runs all day, two rooms have low air flow! Yipes!

    We are renting a 2 year old house, approx. 1600 sq. ft, 1 level. It has a ComfortMaker unit that I think is a 3 ton. Air flow is great in the living room and kitchen, very powerful, so much so that when the unit kicks on you have to turn up the volume on the TV.

    But in the two smaller bedrooms (which are actually closest to the HVAC unit), there is very little air flow and those rooms are about 8 degrees hotter than the others. Even though we have dark curtains on the windows and keep the blinds closed, the system runs NON STOP from 8 AM - 11:30 PM.

    Thermostat is set at 72 degrees. The temp. outside has been from 85 - 95 degrees. We live in SC, so it is only going to get worse over the next few months. Our energy bill for April was already almost $200. Had the freon checked and the tech says it is OK. Any ideas? My toddler cannot sleep b/c her room is so hot.

    Have changed the air filter once per month. I am using a 3M allergen filter.

    Any ideas on what to do next? We have sliding glass doors on the back side of the house, and from 1:00 - sundown the sun is hitting those doors. We keep the vertical blinds closed, but you can feel the heat coming in. Is this a major factor in the house being several degrees hotter than the thermostat is set for? (i.e. set for 72, but is currently reading 76).

    Thanks so much for any advice you can offer. I want to be educated when I call someone out here to look at it. I don't want to waste time or money.

  2. #2
    Join Date
    Jan 2007
    Location
    N.E. Ok.
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    1,371
    1st. the 3m filter is likely to restrictive for your system, they will reduce the airflow needed for your system causing many problems.
    A technician will be needed for the airflow problems, may be simple may not be.

  3. #3
    Join Date
    Jun 2005
    Location
    SW Wisconsin
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    5,022
    Where the plenum is, or where the branch runs come off the main trunk, check for dampers, someone may have closed those dampers on the bedroom runs! A 2 year old house should have dampers on the duct runs, the prior renters may not have slept in those two bedrooms, & closed the dampers.

    Make sure there is NOT hot air being sucked into the Return Air duct system from the attic or garage.

    What size are the ducts? Insulation inside the ducts?

    Everyone living in a home where there is an AC should get a low cost Springfield thermometer/humidity gauge.

    You may also be able to do a lot to reduce the heat-gain in your home.
    Generally speaking, a 3-ton System that is operating properly ought to handle a 1600 SF home, or make changes so it can handle it.

    If you take the right temp & humidity readings, we, (I), can provide a ballpark estimate as to whether the AC is operating close to its Nominal BTUH Ratings.
    - Darrell

  4. #4
    Join Date
    Jul 2005
    Posts
    717
    captube suggested it could be the filter.....I don't think, so because you say the air flow is good in some of the other rooms.
    These 2 smaller bedrooms that have low air flow, do they have any RETURN air in them at all?. If not, then that could be the reason for poor air flow.
    And as udarrel suggested check the dampers to these 2 rooms they may need adjusting.

  5. #5
    Join Date
    Jan 2007
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    N.E. Ok.
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    Quote Originally Posted by deejoe View Post
    captube suggested it could be the filter.....I don't think, so
    Captube suggested the 3m filter is likely to restrictive for the system.

  6. #6
    Join Date
    Sep 2002
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    If you have balancing dampers at the registers, ensure that they are completely open in the bedrooms and partially closed in the kitchen.

    If your ductwork is accessible, check all the seams and takeoffs for leakage; for metal ductwork, foil tape works well.

    If you can't resolve the problem, contact the landlord.

    As the others have said, some 3M filters are very restrictive. The filter is there to protect the equipment, not improve IAQ; a medium efficiency pleated filter should do the job. Do not use any 1" filter rated higher than MERV 8.

    The other thing is that 72F is a very low setpoint; 75-78F offers a better balance between energy consumption and comfort.

  7. #7
    Join Date
    Jan 2002
    Location
    Ft.Worth,Tx
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    I would try and take a look at ductwork that supplies air to those rooms .
    I would also take a look to make sure you have enough return air, sometimes I go to homes with new systems in them with not enough return air grills and unit is noisy and allot of airflow problems exist.

    As for the allergy filter you have make sure you change it ever 45 days, weather it needs it or not. They do restrict airflow if they get dirty.
    "Everyday above ground, is a good day".
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  8. #8
    Join Date
    Feb 2008
    Location
    Western NC
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    2,504
    Being a rental.......

    Your best to contact the landlord and let him know of the situation. If he sends no one out immediately....at least it will be noted for future reference.

    Dampers are likely. The 3M filter is too restrictive. I don't know why people buy them.

    Like said before, the filter is for the eqiupment, not for you. A standard filter (changed monthly) will be fine.

    I would have it looked at and have the system balanced by a technician. This is not something you should attempt yourself. Have it done professionally, that way its done properly and then don't touch the adjustments.
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  9. #9
    Join Date
    Nov 2004
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    SW FL
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    Exclamation There is a problem to define and fix

    Quote Originally Posted by Caitlinem View Post
    We are renting a 2 year old house, approx. 1600 sq. ft, 1 level. It has a ComfortMaker unit that I think is a 3 ton.

    Air flow is great in the living room and kitchen, very powerful, so much so that when the unit kicks on you have to turn up the volume on the TV.

    But in the two smaller bedrooms (which are actually closest to the HVAC unit), there is very little air flow and those rooms are about 8 degrees hotter than the others.

    We live in SC, so it is only going to get worse over the next few months.

    Our energy bill for April was already almost $200.
    Are the doors to the two small bedrooms open?

    Or,
    Is there a duct that is not secure and leaks?
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

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