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  1. #1

    Question 410A High Discharge Temperature.

    I have a Carrier 410A HVAC that keeps tripping the Discharge temperature switch. I have two such systems side by side and I measured the discharge temp and the one that is tripping was 30 degrees F hotter. The system cools the rooms when it is running, but when the outside temp rises above 90F the increase is enough to trip the switch after 4 minutes of operation. So when the A/C is needed the most the unit switches on after the compressor delay and off after 4 minutes. Water cooling the compressor will make it run indefinitely.

    There is some sweating back to the condensing unit. The unit that works well, has a lot of sweating all the way to the compressor.
    I checked the refrigerant with the superheat method and the calculated value was 61F and the measured was 65F. This is certainly within the margin of error. Checking the unit that works well, it appears to be overcharged with calculated = 68F and measured temp =55F

    The system is a 2004 and other than the high discharge temp seems to work fine. There are no service records so I have no idea what if anything has been done to it since installed. It may have always had this issue or it may have just developed this issue.
    I'm thinking its either slightly undercharged or there is moisture in the system.

    Any idea of other tests I might try.

    FYI, I used to operate a refrigeration / A/C repair business back in the late 70's and early 80's. I have been out of the industry since. So 410A is new to me.

  2. #2
    Join Date
    Dec 2005
    Posts
    1,923
    Quote Originally Posted by klatu View Post
    ..

    FYI, I used to operate a refrigeration / A/C repair business back in the late 70's and early 80's. I have been out of the industry since. So 410A is new to me.
    The whole core theory behind this A/C thing has not changed. If you still have not grasped the basic theory 40 to 50 years back, it is time you call the Pro out to help you.

  3. #3
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,062
    Quote Originally Posted by klatu View Post
    I have a Carrier 410A HVAC that keeps tripping the Discharge temperature switch. I have two such systems side by side and I measured the discharge temp and the one that is tripping was 30 degrees F hotter. The system cools the rooms when it is running, but when the outside temp rises above 90F the increase is enough to trip the switch after 4 minutes of operation. So when the A/C is needed the most the unit switches on after the compressor delay and off after 4 minutes. Water cooling the compressor will make it run indefinitely.

    There is some sweating back to the condensing unit. The unit that works well, has a lot of sweating all the way to the compressor.
    I checked the refrigerant with the superheat method and the calculated value was 61F and the measured was 65F. This is certainly within the margin of error. Checking the unit that works well, it appears to be overcharged with calculated = 68F and measured temp =55F

    The system is a 2004 and other than the high discharge temp seems to work fine. There are no service records so I have no idea what if anything has been done to it since installed. It may have always had this issue or it may have just developed this issue.
    I'm thinking its either slightly undercharged or there is moisture in the system.

    Any idea of other tests I might try.

    FYI, I used to operate a refrigeration / A/C repair business back in the late 70's and early 80's. I have been out of the industry since. So 410A is new to me.
    over charged, dirty coil, confined space.

  4. #4
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,776
    Your temp probe or compound gauge is probably inaccurate. You probably don't have a 55 degree vapor temp, with a sat temp of 68.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  5. #5
    Join Date
    Jul 2006
    Location
    Virginia
    Posts
    4,879
    Might be a good time to call a skilled service tech to come find the problem and fix it .the repair will probably involve a garden hose

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