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  1. #1
    Join Date
    Mar 2012
    Location
    Sacramento
    Posts
    36

    High super heat.

    Hey guys,


    I've was checking out my friends system. I have a 9 on my sub cooling target is 10 but my target superheat is 15 my actual is 23, it is a txv system.
    The return supply split, is 77 going in and 66 going out, also it's a r22 system.
    Any thoughts about the low split. Duct work looked ok. I am thinking low on freon.

  2. #2
    Join Date
    Nov 2007
    Location
    Mississippi
    Posts
    1,367
    Pressures? Compressor amps vs FLA? Package unit or is the AHU in an attic? Ambient temp? Where are you measuring return temperature? Need more info

  3. #3
    Join Date
    Nov 2011
    Location
    USA
    Posts
    391
    Normally, 9˚ subcooling is enough to load the evaporator, but have seen a few instances where a few more degrees of subcooling eventually loaded up the coil and brought down the superheat. It's either undercharged, the TXV is underfeeding or there's a liquid line restriction before the TXV.

  4. #4
    Join Date
    Sep 2002
    Location
    The Alamo
    Posts
    3,025
    Slow the fan down.
    Read, read, read!

  5. #5
    Join Date
    Sep 2002
    Location
    The Alamo
    Posts
    3,025
    I mean, check static presure and verify airflow.
    Read, read, read!

  6. #6
    Join Date
    Sep 2002
    Location
    The Alamo
    Posts
    3,025
    350-450 cfm per ton, then adjust freezone.
    Read, read, read!

  7. #7
    Join Date
    Mar 2012
    Location
    Sacramento
    Posts
    36
    Suction line pressure is 67, liquid line pressure is 209psi ambient temp at cu is 89. Indoor wet bulb temp is 67 at return grill suction line temp is 62 liquid line temp is 9. Ahu is in actic.

  8. #8
    Join Date
    Jul 2009
    Location
    Columbia, MD
    Posts
    4,257
    you still dont have all of the info to properly diagnose from across the USA. My guess would be to jump the subcooling up a little more. how long are the lines? you could read 9* at OD unit but really have 4-5* at the a/h due to long lines and attic heat. have you verified that your tools are accurate?

  9. #9
    Join Date
    Mar 2012
    Location
    Sacramento
    Posts
    36
    Lineset is only about 40 feet. When I get back over there I am probably going to make sure the door to the Ahu is sealed up and then add some freon and see if my supperheat drops. So my question is actic air could raise my supper heat but not my subcooling?

  10. #10
    Join Date
    Mar 2012
    Location
    Sacramento
    Posts
    36
    Sorry liquid line temp is 95.

  11. #11
    Join Date
    Dec 2005
    Location
    Cincinnati, Oh
    Posts
    5,096
    fan is moving to much air.
    Or a mix of underfeeding txv + extremly high humidity.
    "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

  12. #12
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,319
    Temp readings are right at the AH, not at registers?

    Leaks in return can add to SH since that is load on evap. 67 wb says it is a bit humid but that alone won't cause 10° drop.

  13. #13
    Join Date
    Jul 2006
    Posts
    1,091
    Why would I check temperature difference? I do it all the time, but only for self satisfaction. If the unit is designed for a SHR above .85 my target TD would be 21 degrees, if my SHR is below .80 my target TD 17 degrees.

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