heat pump problem

Discussion in 'HVAC Heating & Cooling' started by khalsa, Feb 8, 2014.

  1. khalsa

    khalsa New Member

    Messages:
    5
    Location:
    MD
    when i turn the heat on my thermostat the heat pump doesn't come on outside. i can see it start for about a second (the fan moves a tiny bit) and then it stops. it's a carrier performance series heat pump (25hcc542a300). any ideas on where i should start looking?

    thanks!
  2. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,126
    Location:
    Houston, TX
    How cold is it outside ?
  3. khalsa

    khalsa New Member

    Messages:
    5
    Location:
    MD
    it's around 28 F outside and my other heat pump is running fine.
    Last edited: Feb 8, 2014
  4. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,126
    Location:
    Houston, TX
    You may want to feel the compressor and determine if the Crankcase heater is working.

    You may have a bad capacitor.

    Can you hear the compressor safety overload click when it does not start ?
  5. khalsa

    khalsa New Member

    Messages:
    5
    Location:
    MD
    I was missing it before, but the fan on the heatpump actually runs for 7-8 seconds every time I turn the thermostat off and back on (after 5-10min or so) as it's turning off I can hear what sounds like pressure releasing and a single small click sound (is that the internal overload?) as the fan is near to a stop.

    Any ideas? I think I need to call this in, but I'd like to give them an idea what the problem might be.

    The unit's compressor is under warranty, but the rest is past. Should I talk to Carrier first?
    Last edited: Feb 10, 2014
  6. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,126
    Location:
    Houston, TX
    You may be hearing the head pressure equalizing in the compressor, after it kicks off on overload. The Reversing Control Valve may be stuck. It could be a number of things.

    Some units are not made to run below freezing, not sure about that one. I did not find much info on the model number that you provided. Below 32F and efficient drops way down.

    Is your Aux heating strips working ?

    It may be best to call the Man.


    Good Luck.
    Last edited: Feb 10, 2014
  7. khalsa

    khalsa New Member

    Messages:
    5
    Location:
    MD
    Is this what you mean about it (the fan?) not running below freezing?

    someone showed me the installation instruction manual here http://iompics.com/downloads/Heat P...e/Install Instructions 25HCC5/25hcb-c-5si.pdf
    and I saw this:

    Defrost
    The defrost control is a time/temperature control which has field
    selectable settings of 30, 60, 90, or 120 minutes, factory set to 90
    minutes. These settings represent the amount of time that must pass
    after closure of the defrost thermostat before the defrost sequence
    begins.
    The defrost thermostat senses coil temperature throughout the
    heating cycle. When the coil temperature reaches the defrost
    thermostat setting of approximately 32_F (0_C), it will close,
    which energizes the DFT terminal and begins the defrost timing
    sequence. When the DFT has been energized for the selected time,
    the defrost cycle begins. Defrost cycle is terminated when defrost
    thermostat opens, or automatically after 10 minutes.
  8. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,126
    Location:
    Houston, TX
    Yep Yep.

    You may want to try after it gets a bit warmer.

    It could be going into defrost.

    Is your electrical strip heating working ?

    If so it may be best and cheaper to use that, when below 32F.


    Good Luck.
  9. khalsa

    khalsa New Member

    Messages:
    5
    Location:
    MD
    Thanks.
    It is working fine. If it is going into defrost, I think it stays there-- but I can't hear anything. I'll check it out in a few days once the temps reach over freezing. I will keep you posted.
    Last edited: Feb 10, 2014
  10. nukeman

    nukeman Nuclear Engineer

    Messages:
    711
    Location:
    VA
    My guess is it is something else. Even if it goes into defrost, the fan (outdoor) will stop, but you will still hear the compressor run. The defrost will terminate when either the coils warm up enough or if it has been in defrost for 10 minutes. At that point, it will go back into normal operation.

    With the defrost timer set to 90 minutes, the coil must be freezing for 90 minutes before the defrost cycle begins. So, it goes like this (when in heat mode):

    1. coil temperature sensed below 32F
    2. defrost thermostat closes and starts timer
    3. if the defrost thermostat remains closed until timer expires (90 minutes w/ factory settings), the defrost cycle will start
    4. when defrost is complete (or if 10 minutes has past) it goes back into normal operation and the steps repeat

    If ambient temperature are low (below 32F), the coils will be even colder (how a heat pump works), so you will get 1 defrost cycle every ~90 minutes with those settings.

    I would get a tech to look at it (or we can dig more into it, if you are comfortable). It could be something related to the run capacitor or it may be locking itself out to protect the compressor (low pressure, etc.).

    For the crankcase heater, it only specifies one being needed if the lineset is 80' or longer (or if outdoor unit 20' lower than indoor unit). My unit is a different brand and does not use a crankcase heater.
  11. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,126
    Location:
    Houston, TX
    I agree with Nukeman, that was a great explanation of how the system Should work.

    There are many things that can hose the sequence of events.

    If it is a bad Capacitor and it is very cold, sometimes heating them up will help get the electrolytic in them work better and can increase the capacitance. A hair dryer can do that, just for a test. It is best just to measure them, and a good technician will have the proper tools.

    If it is in warranty you are better off to call the man, but a service call for labor can get expensive, even if parts are under warranty.

    As Nukeman pointed out you could have a refrigerant leak.


    Good Luck.
  12. airtrackinc

    airtrackinc New Member

    Messages:
    1
    Location:
    Ontario
    Start and run capacitors are commonly replaced when the system is not starting or running correctly.

    If you suspect the start or run capacitor to be faulty, disconnect all external wiring from the start capacitor. Ensure power is off and proper safety precautions are taken. Ensure that there is no charge in the start capacitor. This can be accomplished by using an touching both terminals with the same metal object at the same time (some like to use a screwdriver with a an insulated handle). Make sure that your hands are insulated from the metal so that you don't get a shock!

    Using an ohmmeter, test both terminals. If the reading is infinite, the capacitor is good. If not, the capacitor should be replaced.
  13. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,126
    Location:
    Houston, TX
    If the capacitor is open, that test will tell you nothing.

    You should reverse meter leads and the reading will be close to a short, for a very brief period, because you are reversing polarity, and then go to infinite if the cap is charging and is not shorted.

    I think you just missed a step, but the precautions given are good.
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