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  1. #1
    Join Date
    Jan 2012
    Location
    York,PA.
    Posts
    34

    What Am I Missing?

    Two Luxaire Furnaces- Model #PBFMD12F08501A and Model#PBFMD12F05501A.Both Furnaces Use The Same Blower Motor And Wheel With Different Airflow Ratings.Something Has To Regulating Flow On The Smaller Output Furnace.
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  2. #2
    Join Date
    Jan 2012
    Location
    York,PA.
    Posts
    34
    No,All unit dimensions,filter & duct openings are identical.It almost has to be electrical.

  3. #3
    Join Date
    Jan 2012
    Location
    York,PA.
    Posts
    34
    Quote Originally Posted by Jeff P View Post
    No,All unit dimensions,filter & duct openings are identical.It almost has to be electrical.
    Here is wiring diagram:
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  4. #4
    Join Date
    Jul 2004
    Location
    Charleston, SC
    Posts
    930
    Smaller furnace has higher pressure drop across furnace section?
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  5. #5
    Join Date
    Aug 2004
    Location
    S.E. Pa
    Posts
    6,056
    Bigwave, This is the Ask Our Pro's or AOP forum. In order to post responses here, you must have verified qualifications and have been approved by the AOP Committee. Please see my signature line for links to register and review the AOP Forum Rules. Thank you. Your post will now be deleted. Further infractions may result in loss of posting privileges.

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    66,808
    Probably has baffles in the smaller one to make sure air flow goes over the heat exchanger. And not bypass it.
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  7. #7
    Join Date
    Jan 2012
    Location
    York,PA.
    Posts
    34
    Thanks beenthere.I have seen low firing rate baffles mentioned after searching it.This is the only PDF I have found:http://www.hamiltonhomeproducts.com/...s/Pfm-tech.pdf

  8. #8
    Join Date
    Jun 2010
    Location
    Philadelphia PA
    Posts
    2,159

    2 different airflows

    means 2 different pressures with this twinned unit SO the unit with the higher pressure is stopping the air delivery from the smaller unit. Not good since winter operations could see high limit trips and cooling will have frozen coils.

    The units need to be balanced airflow regardless of dischagre temp. The air will mix so no need to worry.
    You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!

  9. #9
    Join Date
    Jan 2012
    Location
    York,PA.
    Posts
    34
    I take it this is a bad design.Adding baffles to reduce airflow to save manufacturing costs.I am looking into natural gas.(line is appx.350' away) and hopefully get rid this fuel hog furnace.

  10. #10
    Join Date
    Mar 2005
    Location
    burlington county n.j.
    Posts
    9,642
    Quote Originally Posted by beenthere View Post
    Probably has baffles in the smaller one to make sure air flow goes over the heat exchanger. And not bypass it.
    if the cabinets are the same size it would make sense to have baffles and a smaller heat exchanger.

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