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Thread: need some help

  1. #1
    Join Date
    Apr 2012
    Posts
    44

    need some help

    I have been working on a 2 ton trane system, installed in '01, 410a unit, and cant seem to get it right.
    I went out first call, found head press low, suction press low. added freon, couldnt get pressures to increase no matter how much i added.
    Checked evap coil with camera, nice shiney clean, pulled blower to check secondary xchanger, shiney clean, blower clean. Cleaned condenser coil.
    No change in operation. Figured TXV sticking open. Replaced TXV. Vac. down to 400 microns, holding good. Open system up & run. Running great, charged to 12 deg. subcool. Dropped house temp from 78 to 75 in about an hour. Good to go.
    Calls back later that day, not keeping up. Go out start unit, head press up to 450. Recover some freon, down to like 300 psi running press. Run system, check things over while running, like clogged drain trap, check temp drop across coil, 77 deg. r.a., 55 deg supply side. End up adding small amount of freon to get to 12 deg SC. House cooling down good. Call last nite, not working, 80 deg in house. I guess what i'm wondering is after a couple hours of running, could the compressor be getting hot and bypassing gas or something?? Did not do an amp draw, but will today. More less hoping typing this out would make me think of something i missed.
    When i left yesterday this is what i had
    Indoor temp - 79
    outdoor temp - 83
    Head press - 295
    Suct. press - 125
    subcool - 12- 14 deg
    22 deg drop across coil
    No evidence of water around furnace, and H.O. says blowing good at reg's., so its not icing up.
    Any ideas are appreciated.

  2. #2
    Join Date
    Jul 2005
    Posts
    5,359
    Superheat?

  3. #3
    Join Date
    Apr 2012
    Posts
    44
    didnt check SH. Usually dont on TXV system.

  4. #4
    Join Date
    Apr 2012
    Posts
    44
    Suction line was cold & condensating at the service valve tho.

  5. #5
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,395
    Quote Originally Posted by ottawaair
    didnt check SH. Usually dont on TXV system.



    How are you going to know if the evaporator is properly fed without measuring Superheat?

  6. #6
    Join Date
    Apr 2012
    Posts
    44
    The TXV systems I install give me a target subcool temp on the label. I will check it when out today tho.

  7. #7
    Join Date
    Jul 2005
    Posts
    5,359
    Quote Originally Posted by ottawaair View Post
    didnt check SH. Usually dont on TXV system.
    You MUST check it. How else do you determine whether the TXV is working properly?

  8. #8
    Join Date
    Feb 2010
    Location
    NE Alabama
    Posts
    301
    SH is definitely an essential part of the equation for me.

  9. #9
    Join Date
    Dec 2002
    Location
    Arizona
    Posts
    4,308
    You may have a CFM dropping out late in the day. Just a thought.
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  10. #10
    Join Date
    Apr 2012
    Posts
    44
    I considered the blower tripping out after time, but I see no evidence of coil freezing. And homeowner says still blowing good at registers.

  11. #11
    Join Date
    Dec 2002
    Location
    Arizona
    Posts
    4,308
    I'm talking about your condenser fan motor.
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  12. #12
    Join Date
    Nov 2007
    Location
    Tucson, AZ
    Posts
    95
    Take Micro farad reading of caps take amp reading of comp, cond and blower.
    Check bearings in cond fan motor. Take SH and SC Always when charging or trouble shooting!
    maybe restriction across the filter drier! whats the temp on each side?
    Bruce

  13. #13
    Join Date
    May 2005
    Location
    South
    Posts
    580
    Tell the customer to see if the outdoor unit is running if this no cool situation comes up again. (of course the answer will be yes if the cfm is turning).

    I'd check the electrical components in the cond unit, replace the low voltage wire nuts since they're always exposed to weather on most tranes I've seen.

    I've even seen the thermostat batteries leak and corrode the circuit board on some brands and cause all sorts of weird intermittent problems.

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