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  1. #1
    Join Date
    Feb 2005
    Posts
    19
    New installed complete 5 ton system with TXV. The discharge thermostat is shutting condenser off after about 2.5 - 3 hours of run time. Then after about 2 hours the condenser runs again (discharge thermostat resets itself).

    I checked customers subcooling, it is 18. I am thinking system is over charged. System is a 12 Seer Armstrong.

    If I have this right I need to lower subcooling to around 12-15 by letting out some freon. I do not know what the subcooling should be for sure on an Armstrong unit. Can someone inform me what it is for an Armstrong 12 Seer?

    The 18 subcooling is making the compressor run harder and causing higher discharge pressure which causes higher discharge temperature. Thus causing the discharge thermostat to over heat and shuts the condensor off.

    Do I have this right?

  2. #2
    Join Date
    Aug 2003
    Posts
    290
    so you took some freon out ....and all was okay?

  3. #3
    Join Date
    Feb 2005
    Posts
    19
    No I have not taken any freon out yet as I wanted to be sure I have this correct and the proper subcooling reading I should come to when I take some out. House is empty so will not bother anybody if condesor shuts off for 1 1/2 hours.

  4. #4
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,981
    I don't like to see 18º subcooling. Too much liquid is stacking up in the condenser. I would adjust the subcooling to 12-15º, then check to be certain the TXV is providing the proper superheat.
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  5. #5
    Join Date
    Feb 2005
    Location
    Dothan, Al
    Posts
    3,453
    If 18 subcooling, then vapor is turning to liquid inside the outdoor coil, removing refrigerant would cause a higher subcooling no. as less vapor in the outdoor unit will cause less time to condense, causing the saturation point to move further inside condenser.
    the question is what is causing the temp to rise enough to open the thermostat.

  6. #6
    Join Date
    Jan 2004
    Location
    Midlothian, Virginia
    Posts
    195
    removing r22 would lower subcooling and head pressures if the system is over charged and not restricted. removing the excess liquid in condenser gives the gas more space to give off heat and become a liquid which is good.
    Goodbyee stranger it's been nice. Hope you find your paradise! Hey it aint rocket science, "It's a Trade !"

  7. #7
    Join Date
    Feb 2005
    Posts
    19
    Everything in the system is new and it is R22.

    Last 2 responses said to do opposite things (one said ad freon the other said to remove freon).

    Sysytem has sight glass and it is clear and dry.


  8. #8
    Join Date
    Feb 2005
    Posts
    19
    gauge reading were 70 low side and 142 high side. Outdoor air tempature around 90.

  9. #9
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,981
    resolutetech is correct, I'm not sure that bornriding has proofread his post

    Pressures alone tell us absolutely nothing other then a very basic range of info (OK, if the head is 300 and the suction is 20, there is a problem).

    You mentioned subcooling; what are you calling subcooling?

    142 head seems low for a 90º day, but could be with some higher efficiency systems.
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  10. #10
    Join Date
    Apr 2002
    Location
    Omaha, NE
    Posts
    1,561
    Originally posted by RoBoTeq
    142 head seems low for a 90º day, but could be with some higher efficiency systems. [/B]
    Sounds impossible to me. 142 PSI corresponds to about 79°F.SCT which is 11°F. BELOW outside ambient air temp. of 90°F.

  11. #11
    Join Date
    Feb 2005
    Posts
    19
    I was giving you pressures off the r22 scale.

    On PSI scale pressure would be 70 low side and 210 high side with pressure temp of 106 and line thermostat temp was 88.

  12. #12
    Join Date
    Jun 2003
    Location
    Florida
    Posts
    9,548
    Subcooling should be around 12-15, but you need to measure your superheat to see what's happening in the system. those pressures seem low for 90 degrees, but without more readings it a guess. SH/SC,ambient, delta t,ect.
    If everything was always done "by the book"....the book would never change.

  13. #13
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,981
    Originally posted by stvokc
    I was giving you pressures off the r22 scale.

    On PSI scale pressure would be 70 low side and 210 high side with pressure temp of 106 and line thermostat temp was 88.
    I for one have no idea what any of this is supposed to mean. Are you in the HVAC business?
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


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