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  1. #1
    Join Date
    Feb 2012
    Location
    Atlanta, Ga
    Posts
    20

    Is this normal operation?

    Rooftop package unit with TXV
    Discharge pressure 285
    Suction pressure 70
    Sub cool 11
    Superheat 30
    Suction line temp 70*
    Air across coil is 81* return and 61* supply

    Also it was 96*F on the roof
    Is the TXV stuck closed?

  2. #2
    Join Date
    Feb 2005
    Location
    In a van by the river
    Posts
    621
    No, it actually appears to be proper. TXV appears wide open but under a high heat load. A closed txv would give you a low suction pressure, high sub cooling, high superheat with a low delta T.
    ## + years in the field never made you a know-it-all This industry is far more diverse than you are

  3. #3
    Join Date
    Feb 2012
    Location
    Atlanta, Ga
    Posts
    20
    Quote Originally Posted by git-r-dun View Post
    No, it actually appears to be proper. TXV appears wide open but under a high heat load. A closed txv would give you a low suction pressure, high sub cooling, high superheat with a low delta T.
    That's what I told the owner that the system is running at max capacity. She doesn't believe me, said it used to run cooler inside. It is almost 100*F outside and the store front is west facing with all window.
    When I came to check the system, it was overcharge and cut off on high pressure. It was 106*F outside.

  4. #4
    Join Date
    Jun 2012
    Location
    Delaware
    Posts
    14
    They always say that when it is a 100 degrees out.

  5. #5
    Just a question,,,, what is the refrigerant you are working with on this system?

  6. #6
    Join Date
    Jul 2011
    Location
    East coast USA
    Posts
    976
    Quote Originally Posted by alex13177 View Post
    That's what I told the owner that the system is running at max capacity. She doesn't believe me, said it used to run cooler inside. It is almost 100*F outside and the store front is west facing with all window.
    When I came to check the system, it was overcharge and cut off on high pressure. It was 106*F outside.
    Is this a Carrier RTU? sound like one of mine...lol. but i have to agree this unit is balls out doing what it can.

  7. #7
    Join Date
    Jul 2007
    Location
    Mount Airy, MD
    Posts
    7,281
    Looks pretty good but I question the Back pressure a little with an 81* return.....

    If the condenser is a little dirty and a 285 head.... although that looks good and the Compression ratio looks pretty good, it could fool you if ya had a little dirt.... The compression ratio that is...

    SC and SH look good.....

    But would love to know the DSH, the 3rd piece in the puzzle

    You could have a slightly week pump and sized on the edge.....

    I would check it and pump it down "if" possible.

  8. #8
    Join Date
    Jun 2012
    Posts
    19
    How do you know it was overcharged? Are we positive the condenser is clean? Did you recover and weigh it?

  9. #9
    Join Date
    Jul 2012
    Location
    Phily
    Posts
    6
    Just a thought how much O.A. is coming in

  10. #10
    Join Date
    Feb 2012
    Location
    Atlanta, Ga
    Posts
    20
    Quote Originally Posted by Notasupertech View Post
    Just a question,,,, what is the refrigerant you are working with on this system?
    R22

  11. #11
    Join Date
    Feb 2012
    Location
    Atlanta, Ga
    Posts
    20
    Quote Originally Posted by Aalmaraz View Post
    How do you know it was overcharged? Are we positive the condenser is clean? Did you recover and weigh it?
    Yes, I cleaned the condenser after I saw the discharge pressure was like 350 and suction was above 100

  12. #12
    Join Date
    Apr 2012
    Location
    So. Fl.
    Posts
    57
    Possible dirt impacted in between the coils, check your condenser discharge air along the circumference of the coil. If you have sections where discharge air temp is greater that's where the dirt is and the coil is dirty. Next: change the the drier, yes carrier rtu's do sometimes allow too much out door air in to system.

  13. #13
    Join Date
    Feb 2007
    Location
    Central NJ
    Posts
    519
    Quote Originally Posted by Stohr View Post
    They always say that when it is a 100 degrees out.
    yep... people aren't too bad during heating season but seem to loose their sanity during cooling season.
    You have to pay your due's before you pay the rent!

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