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  1. #1
    Join Date
    Jul 2010
    Posts
    4

    Subcool low and Superheat high

    I had a new goodman heat pump 410a 15 seer and air handler unit installed last week. The installer had overcharged it the first time and had to return to cool the compressor and remove coolant. I dont feel it is working as it should after research on the proper method to ensure the superheat and subcool are within range. I had called another tech to check his work and now this one states the TXV is stuck open and liquid is returning to the compressor. This is the head and suction pressure he reported 304/156 liquid line temp 96 degree and suction line temp 56. I did the math using the chart and came up with a superheat of 37 and subcool of 7. First, can someone help me with making sure Im correct with my numbers, and second will a small charge correct the issue or do I need to adjust the TXV?

  2. #2
    I think you need to have the original installer back out and fix it.

  3. #3
    Join Date
    Jul 2010
    Posts
    4
    Thats the problem, I'm not sure he knows the problem.

  4. #4
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,125
    Without knowing what the line temps measured. We can't confirm that your math is right.
    If the suction line temp was 56, you have virtually no SH, only 1.2.
    If you have 37 of SH, then the suction line temp would need to be 91.

    It looks like you posted saturation temps, not measured line temps.
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  5. #5
    Join Date
    Jul 2010
    Posts
    4
    I will get another pressure and line temps this weekend and repost them and go from there.

  6. #6
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    4,989
    Quote Originally Posted by phlrbear View Post
    I had a new goodman heat pump 410a 15 seer and air handler unit installed last week. The installer had overcharged it the first time and had to return to cool the compressor and remove coolant. I dont feel it is working as it should after research on the proper method to ensure the superheat and subcool are within range. I had called another tech to check his work and now this one states the TXV is stuck open and liquid is returning to the compressor. This is the head and suction pressure he reported 304/156 liquid line temp 96 degree and suction line temp 56. I did the math using the chart and came up with a superheat of 37 and subcool of 7. First, can someone help me with making sure Im correct with my numbers, and second will a small charge correct the issue or do I need to adjust the TXV?
    Well, 304-psig is 96-F SCT, therefore the suction line would have to be 89-F to get 7-F subcooling.

    A 156-psig is 55-F SST, a 56-F suction line would be around 1-F superheat. Many heat pumps use 10 to even 7-F TXV superheat.

    Appears beenthere nailed it, you appear to be using the pressure saturation temps.

  7. #7
    Join Date
    Jul 2010
    Posts
    4
    OK it does look like I miscalcuated the superheat. Now what should be done to correct the subcool problem of 1 deg. To much coolant or to little?

  8. #8
    Join Date
    Dec 2005
    Location
    Cincinnati, Oh
    Posts
    5,047
    Quote Originally Posted by phlrbear View Post
    OK it does look like I miscalcuated the superheat. Now what should be done to correct the subcool problem of 1 deg. To much coolant or to little?
    Your still not providing the neccessary information. Line temperatures are needed. Call back the installer.
    "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

  9. #9
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,692
    Quote Originally Posted by phlrbear View Post
    OK it does look like I miscalcuated the superheat. Now what should be done to correct the subcool problem of 1 deg. To much coolant or to little?
    Starting to venture into DIY territory.

    Even if you don't use the info for DIY purposes, someone else might.

    A good tech would see a charge related problem pretty quickly.

  10. #10
    Join Date
    Jan 2010
    Posts
    6,327
    Stacking up

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