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  1. #1
    Join Date
    Dec 2011
    Location
    British Columbia, Canada
    Posts
    53

    Need help diagnosing Goodman heat pump problem

    I have been in the hvac industry for 17 years but heat pump repairs are not too common for me. I want to be great at what I do but lack experience in this area.
    I was called to a one year old Goodman heat pump install that was apparently noisy, gave no heat, and froze up in heat mode. I like to start from scratch so I checked out everything. It is a 5 ton, 2 stage unit but it was only wired as a single stage, the thermostat setting were all wrong, the blower was only moving 1300 cfm, the furnace has return air on right side only(no way you can move 2000 cfm through that), capillary tubes off outdoor txv were rubbing and vibrating so much that they almost made a hole in the tubing. Phew, I think that's most of it. I am trying to be thorough.
    It has a piston at the coil but I have not checked the size yet. I had 5 degrees of superheat, with a 57F od ambient and 51F wet bulb. It works well in cooling mode. I switch to heating mode, and it runs for only a few minutes before the outdoor txv freezes up and the compressor shuts off. The condensor fan continues to run so I assume this is the defrost cycle?
    I really want to learn so could you please help me understand?

  2. #2
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,915
    Well, you definitely don't have enough indoor airflow.

    Those old Goodman 2 speed units specifically REQUIRE a TXV on the indoor coil. It is in the installation instructions AND on a sticker on the control box cover inside the unit.
    With that system, there is no such thing as "correctly charged" if it has a fixed orifice on the indoor coil.
    With just having an orifice inside, I would strongly recommend against "fixing" the control wiring to allow 1st stage to run by itself.
    If you were to fix it so it would use both stages, and adjusted the refrigerant charge so it is "correct" in 2nd stage, the system will be over charged for 1st stage.
    If you adjust the charge so it is "correct" in 1st stage, the system will be under charged for 2nd stage.

    The condenser fan still running when the compressor shuts off is an indication that it is NOT in defrost.

    On those units, the condenser fan is switched on and off by the control board in the unit, so will stay running if the compressor is turned off due to a low or high pressure switch tripping, or the compressor protection module turning the compressor off due to the compressor windings getting to hot.

    You didn't really give enough information to know why the outdoor TXV ices up in the heat mode, or why the compressor shuts off, but they could be related.
    If the outdoor TXV is failed closed, the system would operate "normally" in the cooling mode, but in the heating mode the TXV and distributor tubes can/will frost up, and the low pressure switch would open, causing the compressor to turn off.
    If more government is the answer, then it's a really stupid question.

  3. #3
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,768
    Kind of sounds like they knew it had a problem when it was installed. So they left it only able to run in first stage to prevent the system from locking out on high head in heat mode, and low pressure in cool mode.

    Sat pressures and temps help us to help you. Along with all temp readings including the inside temp.
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  4. #4
    Join Date
    Dec 2005
    Location
    Cincinnati, Oh
    Posts
    5,312
    As far as the staging goes:

    There are some tech's, on heat pumps, that abandon first stage. Homeowner complaints about air temp tip their hand. Then it seems like the HO never calls to complain again.

    Personally, I think I would fix the installation issues and then try and charge the system.
    Charging a 2-stage heat pump, without a txv, is gonna give you problems.
    Model #'s?
    "Better tell the sandman to stay away, because we're gonna be workin on this one all night."

    "Dude, you need more than 2 wires to a condenser to run a 2 stage heatpump."

    "Just get it done son."

    Dad adjusted

  5. #5
    Join Date
    Dec 2002
    Location
    SouthEast NC ICW & Piedmont Foothills
    Posts
    7,635
    1st_ I'll take your word that you're a tech, nothing in the profile to confirm or deny

    2nd_ not near enough information as stated above

    discharge_ psi & temp
    suction_ psi & temp
    liquid_ psi & temp
    ID temp
    coil condition ID & OD

    that'll give us a clue what's happening
    It`s better to be silent and thought the fool; than speak and remove all doubt.

  6. #6
    Join Date
    Dec 2011
    Location
    British Columbia, Canada
    Posts
    53
    Sorry, you're right. I have more info to offer but with 2 young children and performing heat loss/gain calculations in the evenings, I guess I rushed.
    I am a tech and will fill out my profile ASAP.

    Furnace model was the variable 95090 with 5 ton blower. Sorry, didn't record it.
    Heat pump model number is SSZ160601AE
    Indoor coil model not known but is an 060.
    Condition of both coils is good and clean
    Outdoor ambient is 57F
    Indoor temp is 66F
    Indoor wet bulb is 51F
    Suction pressure is 101 psi
    Suction line temp is 37F
    Liquid leaving temp is 57F
    Liquid pressure is 173
    R410a system

    Yes, it was running on 2nd stage only. Maybe the original tech knew of a problem. He was a refer mechanic in his 60's but passed away a month ago. I've been to several of
    His jobs that look and work great but this one is out of his character.

    Anyway, I hope this all helps. I am suspecting a failed outdoor txv. What would cause it to fail closed?

  7. #7
    Join Date
    Dec 2002
    Location
    SouthEast NC ICW & Piedmont Foothills
    Posts
    7,635
    is that liquid psi from the small pipe or the insulated pipe?

    txv failure-cap tube rub, crimp around head of txv leak, previous leak....

    the info passed on will be limited because of open forum
    It`s better to be silent and thought the fool; than speak and remove all doubt.

  8. #8
    Join Date
    Jul 2002
    Location
    SE Texas
    Posts
    460
    Quote Originally Posted by HomesteadHVAC View Post
    ...capillary tubes off outdoor txv were rubbing and vibrating so much that they almost made a hole in the tubing.
    This caught my attention. Did you look at capillary tube coming from the power element.
    With your chrome heart shining in the sun, long may you run.

  9. #9
    Join Date
    Dec 2011
    Location
    British Columbia, Canada
    Posts
    53
    This is liquid psi measure off the 3/8 service valve.

    It should be noted that when i read pressure from the 3rd port( i don't know what else to call it), I had a negative reading. Could this be from a closed txv, which is shutting off the compressor?

    I did not look specifically at the capillary coming from the power element. I assume that by this, you mean the solenoid?

  10. #10
    Join Date
    Dec 2002
    Location
    SouthEast NC ICW & Piedmont Foothills
    Posts
    7,635
    that psi port alone by itself is the suction psi tap in heat mode

    capillary from power head to bulb


    me believes you just found your problem
    It`s better to be silent and thought the fool; than speak and remove all doubt.

  11. #11
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,768
    Quote Originally Posted by HomesteadHVAC View Post
    This is liquid psi measure off the 3/8 service valve.

    It should be noted that when i read pressure from the 3rd port( i don't know what else to call it), I had a negative reading. Could this be from a closed txv, which is shutting off the compressor?

    I did not look specifically at the capillary coming from the power element. I assume that by this, you mean the solenoid?

    The third port, is known as the true suction port. Its the suction port in both heating and cooling. And should have the same pressure as the large line when the unit is in cooling mode.

    Are you sure the vapor/large line's service valve is completely open.
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  12. #12
    Join Date
    Dec 2011
    Location
    British Columbia, Canada
    Posts
    53
    I have not checked to see if the service valve is completely open, however this unit has worked well up until recently so it sounds like the rubbing of capillary tubes over the months has caused the txv to fail.
    I will check to see if the valve is fully open when I go back to be sure.

    Do you suppose that the low airflow has caused the capillary tubes to vibrate in the first place?

  13. #13
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,768
    Quote Originally Posted by HomesteadHVAC View Post
    I have not checked to see if the service valve is completely open, however this unit has worked well up until recently so it sounds like the rubbing of capillary tubes over the months has caused the txv to fail.
    I will check to see if the valve is fully open when I go back to be sure.

    Do you suppose that the low airflow has caused the capillary tubes to vibrate in the first place?
    Its possible.
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