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  1. #14
    Join Date
    Jan 2009
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    Indiana
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    3,228
    i am thinking its your transformer. u may have 24 Volts but the VA may have dropped..Enough voltage to do the job just just not enough ass behind it.

  2. #15
    Join Date
    Mar 2003
    Posts
    7,326
    define good low voltage, at around 22 you will have trouble pulling in contactors.possibly transformer tapped wrong?

  3. #16
    Join Date
    Nov 2006
    Location
    Southeastern Pa
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    18,557
    Quote Originally Posted by garytulsa View Post
    Can anyone help with this one? I have this 12 ton carrier package unit that has a call for cooling but compressors arent running or outdoor fans. I got voltage but contactors are not engaging. I was told to just hit the disconnect and give it five minutes and turn it back on and it will run. I took a look at it and and found the contactors wont pull in, with a little nudge they suck right in. any ideals what i can look for. model number 48 HJF 012 571HQ thank you for any help.
    This could be more than one issue. The behavior of pushing in the contactors and they hold is the classic reset of the CLO, compressor lockout board. Your unit has two of these little boards, with a power wire passing through a metal sensing loop.

    When you look at the unit, and you have a call for cooling at Y1, make sure you have the same voltage coming back from the economizer, if you have one.

    Then BEFORE pushing in the contactor, look for the control voltage at the coil terminals. If it is not there, and then, if you push in the contactor and it holds, you have a lockout issue.

    If that is the case, start checking everything else. Pressures, superheat, subcooling, condenser and evap delta T, fan operation, etc.

    I have seen low suction pressure as the number one cause of compressor lockout on these Carrier units.

    If you have voltage at the compressor contactor and it does not pull in, measure the current. Does the current change if you:

    a) jump R to Y1 at the terminal strip?

    b) eliminate the Y1 circuit from the economizer? (use the economizer plug or jump the terminals on the economizer logic module)
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist

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  4. #17
    Join Date
    Nov 2006
    Location
    Southeastern Pa
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    18,557
    Quote Originally Posted by yellowirenut View Post
    i am thinking its your transformer. u may have 24 Volts but the VA may have dropped..Enough voltage to do the job just just not enough ass behind it.
    By that, the meaning is that you can have 24 volts all day, but a high resistance in the circuit can limit current flow, and that will keep a contactor from pulling in, even when the CLO is not an issue.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist

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  5. #18
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    Jul 2009
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    Quote Originally Posted by garytulsa View Post
    I have 3 contactors and all of them are not fully engaging. I did ohm out the contactor coils and they tested good. I am getting good voltage at the relay. I didnt ohm out its coil. Today it ran fine. Seems like every other day and up to three times a day i have to pull the disconnect or just push in the coils. i will check out the line voltage at the disconnect and see if i am gettin a full 440. I am not sure where to go from there. thank you for your help so far.
    Did you check the contactor voltage at the coil before or after pushing them in? Have you checked the voltage with the wires off of the coil? My first guess would be the CLO because when you reset the unit ,it works. check all while it is running and hopefully you will find why it is locking out.

  6. #19
    Join Date
    Jun 2009
    Location
    Bakersfield, Ca
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    1,716
    Quote Originally Posted by yellowirenut View Post
    i am thinking its your transformer. u may have 24 Volts but the VA may have dropped..Enough voltage to do the job just just not enough ass behind it.
    Right, you need va. behind your voltage and if the transformer doesn't have the balls anymore, you know what you gotta do.

  7. #20
    Join Date
    Sep 2009
    Location
    Stumptown,USA
    Posts
    1,251
    Does this unit use semi-hermetic compressors? Also I had a carrier about the size you describe doing the same thing after I rinsed the condenser on a cold day. Somehow when the low pressure switch opens it keeps the contactor from pulling in on it's own. But if you push in the contactor it stays in. Another tech told me that is how carrier locks out some of their gaspacks (CLO board). Check your pressure switches or put tattle tales across them and come back later. I agree with timebuilder and pdrake65.
    Challenge yourself, take the CM test --- Certificate Member since 2004 ---Join RSES ---the HVAC/R training authority ---www.rses.org

  8. #21
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    Jul 2009
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    Quote Originally Posted by yellowirenut View Post
    i am thinking its your transformer. u may have 24 Volts but the VA may have dropped..Enough voltage to do the job just just not enough ass behind it.
    Transformer would be my second guess.

  9. #22
    Join Date
    May 2001
    Location
    Western Wa
    Posts
    1,837
    Check the line voltage. If it's within spec, then find the voltage drop on the low voltage.
    Even in this age of high tech DMMs, a 28V test lamp can be a good friend on the low voltage side, especially dealing with triac or other semiconductor outputs on stuff. Sometimes the high impedance DMMs can lie to you, simply because they are so high impedance.
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  10. #23
    Join Date
    May 2010
    Location
    oklahoma
    Posts
    12
    i have 27v from step down transformer also at relay coil and contactor coil. Thank you all for pointing me in a good direction come monday i'll get back on the roof and see what happens. Again thank you everybody for your help!

  11. #24
    Join Date
    Jun 2006
    Location
    New Jersey
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    4,337
    Quote Originally Posted by garytulsa View Post
    i have 27v from step down transformer also at relay coil and contactor coil. Thank you all for pointing me in a good direction come monday i'll get back on the roof and see what happens. Again thank you everybody for your help!
    You CLO's are locking out, as others have said. I normally check airflow first, since I see more freezestat's locking them out the most.

    Also when checking voltage at contactor, check across the two contactor terminals. Not one and ground.

  12. #25
    Join Date
    Nov 2006
    Location
    Southeastern Pa
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    18,557
    Quote Originally Posted by garytulsa View Post
    i have 27v from step down transformer also at relay coil and contactor coil. Thank you all for pointing me in a good direction come monday i'll get back on the roof and see what happens. Again thank you everybody for your help!
    Just make sure you come back and post what you found to this thread until this is resolved, so that there is a beginning, a middle, and yes, an end to the thread.

    And you are welcome. We are all here to learn and share.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist

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  13. #26
    Join Date
    Jan 2010
    Posts
    6,311
    Quote Originally Posted by garytulsa View Post
    i have 27v from step down transformer also at relay coil and contactor coil. Thank you all for pointing me in a good direction come monday i'll get back on the roof and see what happens. Again thank you everybody for your help!
    Gary,
    Come monday disable two contactors and leave one to quick test transformer.
    Or turn unit off and turn I.D. blower on. Provided all are on same transformer.

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