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  1. #1
    Join Date
    Jul 2011
    Posts
    28

    high sbcooling in heay low in ac

    hey so i did some maintenance on my parents system and found head pressure at 580 with 34 degrees subcoolingin heat check it at ac on 70 degree day and had 5 degrees in cooling . have correct return air, clean filters clean coils. any ideas txv operational on outdoor unit has me stumped 4 ton unit any input would be appreiated thanks

    Danny

  2. #2
    Join Date
    Jul 2005
    Posts
    5,491
    Quote Originally Posted by stemps22 View Post
    hey so i did some maintenance on my parents system and found head pressure at 580 with 34 degrees subcoolingin heat check it at ac on 70 degree day and had 5 degrees in cooling . have correct return air, clean filters clean coils. any ideas txv operational on outdoor unit has me stumped 4 ton unit any input would be appreiated thanks

    Danny
    Looks like an air flow issue despite what you said about air flow. Are you sure the blower was running when you were looking at your gauges? It could be dropping out intermittently.

  3. #3
    Join Date
    Feb 2012
    Location
    Ottawa, Ontario Canada
    Posts
    40
    i would love to help! however your lack of punctuation and lack of information hinders me. Delta T accross both coils, high and low side pressures, superheat and subcoolig are all basic assets when asking for AC help.

  4. #4
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,914
    You had a heat pump running in the heat mode on a 70 day?
    What was the indoor temperature?
    If more government is the answer, then it's a really stupid question.

  5. #5
    Join Date
    Feb 2013
    Location
    Florida
    Posts
    69
    Low indoor airflow, overcharge, possibly both?

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,875
    Quote Originally Posted by mark beiser View Post
    You had a heat pump running in the heat mode on a 70 day?
    What was the indoor temperature?
    If that heating SC check was done when it was 70 outside, its a wonder it didn't go off on high head.
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  7. #7
    Join Date
    Jul 2006
    Location
    Virginia
    Posts
    4,619
    if you had a 80 degree return air and 70 degree outdoor temp might be perfect ,also thermostat does not show correct RA temp
    We really need change now

  8. #8
    Join Date
    Jul 2011
    Posts
    28
    Quote Originally Posted by b-roq View Post
    i would love to help! however your lack of punctuation and lack of information hinders me. Delta T accross both coils, high and low side pressures, superheat and subcoolig are all basic assets when asking for AC help.
    yeah sorry for lack of punctuataion. like i said i checked the subcooling in ac on a 70 degree day and had low subcooling, however in heat mode on a 40 degree day i had 34 degrees. Since you check heat pumps with txvs rather than pistons in subcooling not superheat i did not include that info. I can get the delta t across coils, however head pressure of 586 on a 40 degree day seemed to me to be problematic one way or another. could be wrong. Fan was running and there is 1670 cfm of return air on a 4 ton unit. and please no comments from people who try to put others down with above quotes to make themselves feel better. No disrespect justr don't have time or patience for it. Thanks

    Danny

    od temp 40
    heat mode
    suction 120
    head 586
    subcooling 34
    410a unit
    4 tons

  9. #9
    Join Date
    Feb 2009
    Location
    Tallahassee, FL
    Posts
    6,031
    So you have a outdoor txv ? And a communication variable speed that shows the 1670? Doesn't always mean you are getting it. Not saying that is the problem here though.

    Please provide model and serial of units.

  10. #10
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,914
    Quote Originally Posted by stemps22 View Post
    Since you check heat pumps with txvs rather than pistons in subcooling not superheat i did not include that info.
    You should always check the superheat anyway, since it is an indicator of whether the TXV is operating correctly or not.

    Also, what model of indoor and outdoor units?
    The issue could be related to the equipment matchup.
    If more government is the answer, then it's a really stupid question.

  11. #11
    Join Date
    Jul 2011
    Posts
    28
    yeah i thought about the unmatched possibility ill get the m/s numbers but no i got the trurn air with a ductulator duct is sealed and not kinked so i figured it was pretty close thanks for the tip about superheat though. makes sense.

  12. #12
    Join Date
    Feb 2009
    Location
    Tallahassee, FL
    Posts
    6,031
    This may be a whole nother thread worthy but you how are you using that ductulator?

  13. #13
    Join Date
    Jul 2009
    Location
    Columbia, MD
    Posts
    3,834
    Sounds to be over charged in heating.

    You need 450cfm/ton for heating mode.

    You will have a higher subcooling in heating mode because the ID coil is smaller then the OD coil.

    You're head pressure is too high in heating.

    What are your pressures when you checked in cooling?

    70* is a little cool. If you had lower head pressures this would be why you have lower SC.

    If airflow checks out and you know charge is good (check in a/c) then i would recommend adding a VPS to the OD fan. Carrier used these back in the day on their 410a h/p. If you turn OD fan off it should lower your head pressure.

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