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  1. #1
    Join Date
    Oct 2008
    Location
    Indiana
    Posts
    10

    Angry Trane Rtaa 270 with oil and low suction trouble

    Hi guys and gals need some advice. I have a Trane RTAA270 with the UCM system and I am having problem with two issues with this system. I work at a local university and do not have a ton of experience with the system. I am running a low suction and having a nuisance trip of low oil flow. I know for a fact that the system is charged correctly with 130 lbs of r22. I weighed it in this afternoon. Reading a manual I thought that my problem with this system was over charged. So I fell back and punted. I found a bad condenser sat temp sensor and replaced that. Now the system will run after reset. I have checked all coils for dirtiness and all fans are running correctly. I have checked oil solenoid, load and unload coils for operation. Also checked filter driers. I seen where someone on here posted about pill filters? Also on menu p2 line 27 on the amp reading. Is this reading percentage or actual amps of comp running at the time of start up. I also checked oil switch and system runs for a long while. Also checked oil pressure switch also.
    I also noticed evap limiting code 77. I found a manual about within 6 degrees of set point. Does it use the sensor to determine low pressure cut out.

  2. #2
    Join Date
    Aug 2006
    Location
    Mixing oil and fire with a big spoon.
    Posts
    4,336
    sounds like you are doing some homework...good job.

    the displayed value in menu #27 is %RLA.

    do you have glycol in the system? if yes, what type and how much?

    what are these menu settings?
    1. 40
    2. 41
    3. 49
    4. 4A
    5. 4B
    6. 52

    also keep in mind that all pressures are converted from temp sensors

    good luck.
    "Mother" is the name for God on the lips and hearts of children....The Crow

  3. #3
    Join Date
    May 2001
    Location
    Western Wa
    Posts
    1,831
    Superheat and subcooling?

    Actual, not calculated.
    God Bless our Veterans

    God Bless the USA

  4. #4
    Join Date
    Oct 2008
    Location
    Indiana
    Posts
    10
    hey guys did not get to work on it today. had a couple barber coleman actuators and a trane dx unit to repair.

  5. #5
    Join Date
    Oct 2003
    Location
    tidewater, va
    Posts
    2,136
    Check amp draw at start up, this one maybe be starting loaded.

    r404a

  6. #6
    Join Date
    Mar 2004
    Location
    ottawa canada
    Posts
    2,042
    I agree with Jayguy . Badtech you have done your homework . Finally a tech who comes on here who has done some reading and some work to try and correct the problem instead of just "it trips on oil flow I guess the oil filters plugged "
    The pill filters are exactly that they are small brass filters fitted in the oil gallerys underneath the solonoids ,there purpose is to remove "start up" debris from unit manufacture .
    it does sound from your description that you have a compressor starting loaded , check item 27menu 2 right after start up it should be no more than 45%, if it is then the piston is stuck and may need a rebuild .
    you can try dissconnecting the load/unload solonoid wires off the ucm and take a jumper and find a 110volt power source in the panel , get the compressor running and put power to the unload solonoid constantly to try and force the piston to unload ,if you can get it fully unloaded then load it up with the jumper (slowly) or you will trip it . do this several times to exersize the piston . If you cant get the amperage to change then bingo time for a rebuild on the piston . good luck Graham
    Ps If you do remove the solonoids to check the pill filters then just remove them and toss them in the garbage they are not needed once the unit has run for a while .

  7. #7
    Join Date
    Mar 2008
    Location
    Florida
    Posts
    193
    Dear Sir, you do a disservice to every tech who has made a comment on this site. As a matter of fact , I can tell you I learn from every comment I read. I appreciate hearing every voice. As trifle as they may sound, all input pertaining to hvacr in my view is welcome to someone. I look forward to meeting that person who knows it all just starting out.

  8. #8
    Join Date
    Mar 2004
    Location
    ottawa canada
    Posts
    2,042
    And your point is ??????????????????????????..............
    I was merely commending badtech for his information and prior work in his diagnostic work and trys at repair . A lot of techs come on here and provide next to no info and ask vague questions and show very little apptitude towards the problem they are trying to solve .
    I gave badtech sound reliable practices and tests and information to help him , obviously you didnt read all the post or any of my previous posts particularly on this subject with the RTAA series chiller ??????
    If you cant provide advice on the post in question then do us all a favour and dont post unnessacary comments .

  9. #9
    Join Date
    Mar 2008
    Location
    Florida
    Posts
    193
    Badtechs' diagnostics, on which you had commented on were good. However; your comment stating: "Finally a tech comes on and does his homework". True, comments of little consequence are made, but finally is a heavy word, which Lead me to believe that no one previously in your eyes has done their homework. Sorry if you felt offended. None were meant.

  10. #10
    Join Date
    Oct 2008
    Location
    Indiana
    Posts
    10
    Hey thanks guys for the info. Also it does not tell me where in the manual to check superheat. Does trane techs do it right after the exv or after it goes threw the evap? Also graham I have read a lot of your post. I am assuming that you are a trane tech. What causes the piston to stick? Does it swell due to age, traces of moisture in system and or overcharged unit? I really do not think it is the oil filter because it runs long after the 20 seconds it would take to trip. Also if it is the piston needing rebuilt do we need to contact a trane tech or is this a job that i can tackle?

  11. #11
    I had a RTAC with the same problems, and found out that the oil return solenoid had failed. Which caused the evap to become oil logged and was tripping on low oil level and low evap temp. I would look for a solenoid on the oil return line and troubleshoot that. Trane tech support directed me to cut out the valve and sweat in straight pipe. I haven't had any trouble since.

  12. #12
    Join Date
    Mar 2004
    Location
    ottawa canada
    Posts
    2,042
    There are two things in common between the RTAA and the RTAC
    1 they are painted the same colour.
    2 they are built in Pueblo .
    Thats it thats all, different refrigerant different evaporator different EVERYTHING???????? there is no oil return line or solonoid so dont look for one .
    The piston changeout is easy if you can use a recovery unit and a vacuum pump , just remember the nuts and bolts are metric and put a tray under the compressor when you remove the end plate to catch the oil.
    Superheat is set and calculated by the UCM using the sat evap and suc temp sensors .
    If.you drain a lot of oil in the piston change out the just remove the flare fitting below the master oil solonoid and pour in the equivalent new amount before you evacuate the compressor .
    Are you sure the piston is sticking and you dont just have a solonoid or problem or possibly a leaking lip seal ??? Item 27 menu 2 amperage????
    There is a very useful service bulletin published that gives all the procedures for checking out load/unload issues for the RTAA.

  13. #13
    Join Date
    Mar 2004
    Location
    ottawa canada
    Posts
    2,042
    Two service bulletins which are very useful for this diagnosis are RTAA-SB-4 and RTAA-SB-12

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