Page 1 of 2 12 LastLast
Results 1 to 13 of 24
  1. #1
    Join Date
    Jun 2013
    Posts
    6

    high superheat normal subcooling

    Have a R404a freezer with -11f evap temp 20f box temp 100f condenser temp. 50f super heat and 10f subcool. 75f ambient and 80%rh. any thoughts why not colder?

  2. #2
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,386

  3. #3
    Join Date
    Jun 2013
    Posts
    6
    Tech

  4. #4
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,386

  5. #5
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,386
    NOW.... Let's get down to this.

    Does the unit have a sightglass? If so, is it clear?

    Are you not in the slightest concerned that the superheat is 50 degrees?

  6. #6
    Join Date
    Jun 2013
    Posts
    6
    Sight glass is clear. I am thinking high superheat is caused by blocked txv?

  7. #7
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,386
    I wouldn't "think" anything. I would investigate and determine WHY these things are happening.

    This is the job of a technician.

    A malfunctioning TEV is a good place to start, but there are a number of reasons that it could be malfunctioning. There are inlet screens that plug up and power heads that fail.

  8. #8
    Join Date
    Jun 2013
    Posts
    6
    there was a large formation of ice on the txv along with the high super heat that leads me to believe the tev has an issue. if the tev is restricted, shouldn't the subcooling be high also?

  9. #9
    Join Date
    May 2003
    Location
    Utah
    Posts
    718
    Since you are a "tech", why don't you state your case for why the TEV restriction should lead to high sub cooling.

  10. #10
    Join Date
    Jun 2013
    Posts
    6
    I am a new tech. i THought that if the tev is partialy blocked the evap would be starved giving me the high super heat and and cause a backing up of the refrigerant in the condenser giving it more time to subcool

  11. #11
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,386
    The problem with that is that, typically, a subcooling measurement on a refrigeration system like this isn't as meaningful as it is in a split residential AC unit.

    You've got a good head pressure and a solid glass and that's about where your liquid side measurements end. Maybe need to look at the possibility of a plugged liquid drier, but other than that...


    I don't think that bunny or I disagree with your assessment of a malfunctioning TEV. What we're trying to get you to do is to think bigger about how the system is operating and how one failure can cause or lead to another.

    Start by examining the TEV inlet screen. That's a very common thing to plug and all you need to do is to clean the trash out of it and start it back up. If that's clean, replace the power element and sit back and see what happens. Maybe measure the pressure drop across the filter drier if possible. Take the temp drop across the filter-drier if not (although this isn't the BEST way to check them)

  12. #12
    Join Date
    Sep 2002
    Posts
    12,195

    R-22 TXV ?

    Any chance it has an R-22 valve on the coil?

    What does the powerhead say?

    PHM
    -------





    Quote Originally Posted by yvnsteve View Post
    Have a R404a freezer with -11f evap temp 20f box temp 100f condenser temp. 50f super heat and 10f subcool. 75f ambient and 80%rh. any thoughts why not colder?
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  13. #13
    Join Date
    Jul 2012
    Location
    Western KY
    Posts
    1,221
    Quote Originally Posted by jpsmith1cm View Post
    The problem with that is that, typically, a subcooling measurement on a refrigeration system like this isn't as meaningful as it is in a split residential AC unit.

    You've got a good head pressure and a solid glass and that's about where your liquid side measurements end. Maybe need to look at the possibility of a plugged liquid drier, but other than that...


    I don't think that bunny or I disagree with your assessment of a malfunctioning TEV. What we're trying to get you to do is to think bigger about how the system is operating and how one failure can cause or lead to another.

    Start by examining the TEV inlet screen. That's a very common thing to plug and all you need to do is to clean the trash out of it and start it back up. If that's clean, replace the power element and sit back and see what happens. Maybe measure the pressure drop across the filter drier if possible. Take the temp drop across the filter-drier if not (although this isn't the BEST way to check them)
    I would actually start cheeper. Try to adjust TEV and see if it will or pull the bulb and hold it in your hand. I'd wanna know if it responds before I take the system down and open it.

Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event