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  1. #1
    Join Date
    Jan 2008
    Location
    Florida
    Posts
    39

    Confused Odd fan/compressor sequence?

    Carrier 5T Heatpump system with a Focus Pro 5000 thermostat.

    While the AC was operating, I raised the temperature 2 degrees. A few minutes the AH fan shut down (after the normal delay), but the compressor kept running, would not turn off even if I took the T-stat out of cool mode. I pulled the outside breaker, turning off the compressor. Now the system works normally: temperature reached, compressor shuts down, a few minutes later the AH fan shuts off.

    What could have caused the compressor to keep going with the AH fan off?

    Could changing the temperature setting on the T-stat have temporarily scrambled something in the T-stat that could have caused this.

    But I thought the AH fan was turned on and off from a contactor at the condensor that also controls the compressor/fan contactor preventing the compressor from operating without sending power to the AH.

    What would have happened if this had happened if I did not pull the breaker?

    Thanks for help.

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,601
    The OD unit doesn't any control over the indoor unit unless its 2 stage.

    Your stat may be wired or configured wrong.

    If its a new install, call your contractor back.
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  3. #3
    Join Date
    Jan 2008
    Location
    Florida
    Posts
    39
    It's not a new install. The system has been working fine this winter in HP mode and this summer in cool. The manual fan control works too.

    It seemed like the stat hung up. Has that happened with this type if the temperature is changed too quickly under certain circumstances?

    The system operating normally now. I am not sure I could duplicate what happened but something did.

    When would the condensor have kicked off and what condition would have caused it? I suppose that the coil would have frosted up, but without air running over it not much ice would have accumulated before the condensor shut itself off.

  4. #4
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,371
    Hard to say for certain what exactly caused your problem. It's possible the triac or relay inside the thermostat that energizes/de-energizes the compressor contactor got stuck on. Also possible the compressor contactor itself got stuck on. When you hit the breaker, the contacts cooled enough to let go...possibly. If the system has a few years on it and you've never had the outdoor compressor contactor replaced, might be a good idea to get that done. Being it's a heat pump, the compressor runs year round, so contactor life is used up more quickly than for straight a/c.

  5. #5
    Join Date
    Jan 2008
    Location
    Florida
    Posts
    39
    New contactor and fan on the condensing unit in January.

    Damdest thing.

    As said before, what would have happened if I was not around, although I suppose if I wasn't the temperature setting would not have been manually raised is some way that caused the odd operation.

    I thought that as long as the compressor contactor was closed, the AH fan would run. It's a SP fan, but runs for about two minutes after the compressor stops. I thought the control for that was in the condensor.

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,601
    Its not.
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  7. #7
    Join Date
    Aug 2005
    Posts
    73
    problem with the stat, if it was wired wrong you would have noticed by now.

    those focuspro stats are pieces of ****, changed a few this year already due to failure..and they were less then 2 months old.

  8. #8
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,601
    haven't had a problem with them. What were they doing or not doing.
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  9. #9
    Join Date
    Aug 2005
    Posts
    73
    i had 2 that decides to "pop out" of there designated equipment mode.

    these have the ability to run 1/2/hp/oil fired/etc type equipment. and you set it for whatever your running, but i had 2 different customers, with completely diff equip, one was a 2 stage rtu, so it was set for 2 stage on the stat. got a call back it was hot, so went back, the stat had set itself to only 1stage system, and wouldnt come out of econo when it was hot. did this 2 or 3 times and just said f-it. changed the stat. same thing happened about a month later at a different customer.


    i never liked the green color anyway

  10. #10
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,601
    Ok, 2 out of how many?
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  11. #11
    Join Date
    Aug 2007
    Location
    MN
    Posts
    2,677
    Quote Originally Posted by Carry On View Post
    New contactor and fan on the condensing unit in January.

    Damdest thing.

    As said before, what would have happened if I was not around, although I suppose if I wasn't the temperature setting would not have been manually raised is some way that caused the odd operation.

    I thought that as long as the compressor contactor was closed, the AH fan would run. It's a SP fan, but runs for about two minutes after the compressor stops. I thought the control for that was in the condenser.
    give the service guy a call, your outdoor equipment needs attention. The stat is not going to keep the condenser on without the air handler on.
    You can't fix stupid

  12. #12
    Join Date
    Jan 2008
    Location
    Florida
    Posts
    39
    Would the compressor have shut down automatically without the AH operating?

  13. #13
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,601
    Depending what model outdoor unit you have, it should have a safety switch that wouold have cycled it if the pressure got too low. Not sure if it would lock it out though.
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