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  1. #1
    Join Date
    Jul 2012
    Location
    Cincinnati ohio
    Posts
    252

    Airflow question

    I would be willing to bet that 95% or more of the two story homes I go to have the registers closed in the basement or first floor trying to force air to the upper level. I hear conflicting answers about this. Some techs say it is a bad idea because it creates high static pressure and actually makes the air flow worse and some say it helps. What are your thoughts?

  2. #2
    Join Date
    Jan 2010
    Location
    new orleans
    Posts
    230
    It's a common problem. Measure esp and air flow for yourself. All homes and duct systems are different.

  3. #3
    Join Date
    Dec 2002
    Location
    Arizona
    Posts
    4,411
    I would say most duct systems are undersized form the get go, so.................. turning half of the supplies off can cause flood back to the compressor on cooling and over heating of the heat exchanger on heating. Not a good idea!
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  4. #4
    Join Date
    Feb 2012
    Location
    North Plainfield ,NJ
    Posts
    58
    Are you a new tech, if so i suggest you take an air balancing class. I'll bet that the designed did not know what he was doing and call the supply house guy to figure that ACCA calculations for him. It seems to me that the ducts were not sized out right. If the ducts were sized correctly,the this would not be an issue.As far as high pressure yes but only way it will not be high pressure is if the blower motor is an ECM motor. As I said in the begining a Air balancing class would be a huge help for you!!!

  5. #5
    Join Date
    Feb 2012
    Location
    North Plainfield ,NJ
    Posts
    58
    A flood on the heat exchanger would set off the high limit off but also consider for yourself the blower is at a lower speed in the winter. I know what I would do but I'm playing teacher and letting you figure things out for yourself because i rather teach you how to fish than give you a fish

  6. #6
    Join Date
    Dec 2002
    Location
    Arizona
    Posts
    4,411
    Quote Originally Posted by jrath66 View Post
    .As far as high pressure yes but only way it will not be high pressure is if the blower motor is an ECM motor.
    Why would that be?
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  7. #7
    Join Date
    Feb 2012
    Location
    North Plainfield ,NJ
    Posts
    58
    Be more specific about post


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  8. #8
    Join Date
    Dec 2002
    Location
    Arizona
    Posts
    4,411
    Are you saying an undersized duct system will not cause high static with a VS motor?
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  9. #9
    Join Date
    Sep 2008
    Location
    VA
    Posts
    1,768
    Quote Originally Posted by meh70087 View Post
    It's a common problem. Measure esp and air flow for yourself. All homes and duct systems are different.
    I agree, all homes and duct systems are different.
    Cutting back a 4 vents out of 25 likely will not cause a problem, but cutting back 4 out of 10 will likely cause some issues. There are many things to consider.
    I would agree check TESP before and after adjustments are made. If you're within mfg spec, then you should be ok.
    "The only true wisdom is in knowing you know nothing" Socrates

  10. #10
    Join Date
    Jan 2007
    Location
    Mn the state where absolutey nothing is allowed
    Posts
    1,351
    Quote Originally Posted by jrath66 View Post
    A flood on the heat exchanger would set off the high limit off but also consider for yourself the blower is at a lower speed in the winter. I know what I would do but I'm playing teacher and letting you figure things out for yourself because i rather teach you how to fish than give you a fish
    huh?

    fishing for a heat exchanger in a flood limit in the lower winter speed?

    Be more specific about post
    Last edited by ch4man; 03-21-2013 at 10:18 PM. Reason: whiskey tango foxtrot moment
    my boss thinks its possible to repeal the laws of physics

  11. #11
    Join Date
    Dec 2002
    Location
    Arizona
    Posts
    4,411
    Are you saying that didn't answer your question? LOL
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  12. #12
    Join Date
    Mar 2013
    Location
    Joplin,Missouri
    Posts
    310
    Check for 121 jigawatts to the flex capacitor at the flooded exchanger ecm winter speed if not close half the vents that should solve the problem lmao seriously though it all depends on how the duct was originally sized and how the system was designed i dont like to see vents closed off completely basements alot of times have too much airflow anyway so it may be okay to damper them down about 50 percent but closing vents off altogether usually just creates hot and cold spots in the house most people dont size the upstairs or a bonus room correctly to begin with so closing a couple vents wont do any good anyway

  13. #13
    Join Date
    May 2007
    Location
    Dry as a bone Tucson
    Posts
    4,344
    Bad idea,really bad.
    Instant red flag for undersized supply to 2nd floor. It's easier to shut dampers on the second floor to get air to the first than shut dampers on the first to get air to the second that is of course all depending on where your blower is located and a thousand other issues...........
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