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  1. #1
    Join Date
    Oct 2003
    Location
    Rockwall Texas
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    4,519

    Default Condensing unit fan motor question

    Can any of you HVAC guru's advise me on why a condensing unit fan motor would run continuously even though the thermostats are in the off position?

    If the breaker at the panel box is switched on, the fan on the condensing unit runs but not high speed, but more in a slower speed.

    Rick

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  2. #2
    Join Date
    Mar 2007
    Location
    Ormond Beach, Florida
    Posts
    26,243

    Default Re: Condensing unit fan motor question

    Not an HVAC guy, but ... something wired wrong would be my guess. Either that or something going bad and allowing a tremendous amount of bleed through current.

    The contactor should keep that off if the contactor is wired correctly and is not pulled in by the thermostat.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  3. #3
    Richard Stanley's Avatar
    Richard Stanley Guest

    Default Re: Condensing unit fan motor question

    May be bad limit switch.


  4. #4
    A.D. Miller's Avatar
    A.D. Miller Guest

    Default Re: Condensing unit fan motor question

    Quote Originally Posted by Rick Hurst View Post
    Can any of you HVAC guru's advise me on why a condensing unit fan motor would run continuously even though the thermostats are in the off position?

    If the breaker at the panel box is switched on, the fan on the condensing unit runs but not high speed, but more in a slower speed.

    Rick
    Rick: One possibility: thermostat is bad or battery is bad AND one side of the bridged breaker is bad. Or, a multi-speed condenser that is malfunctioning?


  5. #5
    Join Date
    Mar 2007
    Location
    Chandler, AZ
    Posts
    119

    Default Re: Condensing unit fan motor question

    For what it's worth, I've seen some units that run the fan to circulate air, but only for about 10 minutes and then it shuts off. It did this even when the thermostat was set to off (not heat or cool mode).

    Of course this was not continuous like you saw.
    BTW, I'm definately not a HVAC guru.

    Dave Hill
    Buyers & Sellers Property Inspections LLC
    WWW.BuyersSellersPi.Com

  6. #6
    Join Date
    Mar 2007
    Location
    Ormond Beach, Florida
    Posts
    26,243

    Default Re: Condensing unit fan motor question

    Dave,

    That is for the AHU, one of the ways they achieve the higher SEER ratings.

    He is talking about the condenser unit outside.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  7. #7
    Join Date
    Mar 2007
    Location
    Ft. Myers, FL
    Posts
    363

    Default Re: Condensing unit fan motor question

    Does it appear that the fan has been changed at some time? Maybe some genius wired to a continuouus power source, like maybe the wrong side of the contactor.

    Paul Kondzich
    Ft. Myers, FL.

  8. #8
    Join Date
    Mar 2007
    Location
    Plano, Texas
    Posts
    4,170

    Default Re: Condensing unit fan motor question

    Bad contactor... but the compressor is typically on the same contactor so I would think the compressor would be trying to run. With the fan motor running at less than full speed it may be one of the older units that just breaks one leg of the 240v and the motor windings have gone to ground part way through the winding. It is just running on 120v until the breaker is shut off. Then when the breaker and contactor are on, the motor runs at nearly full speed.
    IF it is a newer unit with solid state multi-spead fan, then all bets are off. Look at replacing the circuit board.
    If it is a heat pump, make sure you allow time to cycle through defrost delays.

    Jim Luttrall
    www.MrInspector.net
    Plano, Texas

  9. #9
    Darrel Hood's Avatar
    Darrel Hood Guest

    Default Re: Condensing unit fan motor question

    I saw this recently on new construction. The thermostat connection was incorrect.

    Also, I have heard, though not from a credible source, that some High Velocity systems run continuously.

    Darrel Hood
    DILIGENT PROPERTY SERVICES


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