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  1. #27
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,167
    Yes, and yes.
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    How many times must one fix something before it is fixed?

  2. #28
    Join Date
    Dec 2002
    Location
    omaha
    Posts
    343

    Question

    HO stated return air temp. at wall grille 64 that seems a bit low if stat is set to main 74

  3. #29
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    68,167
    In the first post, it was 77, so I took th 67 as a typo.
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  4. #30
    Join Date
    Dec 2007
    Location
    Houston, TX
    Posts
    29

    Not a typo

    beenthere, post stating 64* at intake is not a typo. I am using a refrigeration
    thermometer with about a 5" stem on it and pushing it thru the cheap fiberglass filter. The ubit does have a 5" media filter upstairs, I do not rely on cheap fiberglass filter alone.

    I will post size, length of ducts in a little while.

    Here are some specs from today.

    thermostat left at 74* all day.
    82* outside - intake 64* - rm1 76* in room w/58* at register,
    rm 2 73* in room w/56* at register, rm3 74* in room w/58* at register

    95* outside - intake 65* - rm 1 76* in room w/51* at register,
    rm 2 73* in room w/58* at register, rm 3 77* in room w/62* at register.

    Room 2 seamed to get better ??

    Thanks

  5. #31
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,167
    Sounds like some supply air is traveling across teh ceiling and into the return.

    Remove your 1" filter and try it that way for the weekend.
    2 air filters in series can slow the air down more then you think.
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  6. #32
    Join Date
    Dec 2007
    Location
    Houston, TX
    Posts
    29

    duct specs

    Thanks beenthere, I will remove fiberglass filters.

    Here are the approx. duct sizes. I don't envy you guys crawling around in an attic ! When the new unit was installed the hard pipe was cut back and hooked to plenum with flex. Approx lengths include the flex.

    36' of 12" hardpipe serving 1 register to kitchen
    36' of 16" hardpipe serving 3 registers to den & dining room
    25' of 12" hardpipe serving 2 resisters to bedroom & bath
    12' of 12" hardpipe serving 1 register to bedroom with Y of 7' of 8" to bath
    45' of 5" flex serving 1 register to washroom
    6' of 7" flex serving 1 register to bedroom
    20' of 9" flex with the triangle box then 5' of 7" to bedroom & 25' of 7" to office

    1 20 x 30 hall return & 1 14 x 25 ceiling return

    All I know about cfm is installer told me 400cfm per ton x 4 ton = 1600cfm
    Home is 1950 sq ft
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  7. #33
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    68,167
    The air extra filters out will help alittle. Maybe enough.
    With the majority of your system being hard piped. The flex runs are alittle too restrictive for the air flow you need.
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  8. #34
    Join Date
    Dec 2007
    Location
    Houston, TX
    Posts
    29

    The flex runs are alittle too restrictive

    Quote Originally Posted by beenthere View Post
    The air extra filters out will help alittle. Maybe enough.
    With the majority of your system being hard piped. The flex runs are alittle too restrictive for the air flow you need.

    Does this mean the flex is undersized ?

    I took the filters out for now. Will see if that helps.

    Thanks

  9. #35
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,167
    Not so much undersized for the amount of air needed. As much as for the size of the existing hard ducts. With dampers installed and the hard pipe runs balanced, the flex runs would work fine.

    See how it does for you this weekend.
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  10. #36
    Join Date
    Dec 2002
    Location
    Houston,Tx.
    Posts
    16,008
    Well according to my air duct calculator @.1 static you have enough duct sizes to provide for over 4000 cfm's of air, the air velocity must be terrible especially with those long runs, but at least your volume is good.

    36' of 12" hardpipe serving 1 register to kitchen = 700 cfm's
    36' of 16" hardpipe serving 3 registers to den & dining room =1500 cfm's
    25' of 12" hardpipe serving 2 resisters to bedroom & bath =700 cfm's
    12' of 12" hardpipe serving 1 register to bedroom with Y of 7' of 8" to bath = 700 cfm's
    45' of 5" flex serving 1 register to washroom = 70 cfm's
    6' of 7" flex serving 1 register to bedroom = 150 cfm's
    20' of 9" flex =300 cfm's
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  11. #37
    Join Date
    Dec 2007
    Location
    Houston, TX
    Posts
    29

    How about a little ductwork 101 for dummies

    Does all this mean my hardpipe is hogging all the air and not letting the flex get what it needs ?

  12. #38
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,167
    Air takes the path of least resistance. So without balancing dampers, yes.
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  13. #39
    Join Date
    Jan 2008
    Location
    lexington, kentucky
    Posts
    50
    It means that you have very little static pressure in your duct system. If you put 1600 cfm's into a duct system that will carry 4000 cfm's, by the time that the air gets to the registers, there is no air. I would really like to see the numbers that are produced if the system is tested with a hood at the registers.

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