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  1. #1
    Join Date
    Sep 2005
    Location
    Maryland
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    221

    RTAA 90 Oil Fault Help!

    I have a Trane RTAA0904XJ01A3C0BG that has circuit 1 continuously tripping due to "Oil System Fault-ckt 1". Now, there has been no recent repairs done to this circuit which could have brought in any contaminates, and the refrigerant charge is good. I'll be going in later to check oil level, but I know the oil filter on this system is generally oversized and shouldn't need replaced regularly (per the mfg), and there doesn't appear to be any leaks on this particular circuit (or even a history of leaks for that matter). Do any of you chiller pro's have any insight as to what a common cause is. I know this chiller verifies proper oil charge by means of the oil temp at the separator and the saturated condenser temp, and I believe it faults after 30 mins if there is lower than a 4 degree difference. What could cause this fault or restriction?

  2. #2
    Join Date
    Jul 2009
    Location
    In a mechanical room....
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    1,886
    Fans staging properly?
    Are all of your sensors reading accurately?
    What's your SH/SC
    Do you have a operating Log?
    “It takes courage to grow up and turn out to be who you really are.”

    - E.E. Cummings

  3. #3
    Join Date
    Jun 2012
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    526
    Quote Originally Posted by chrishvacman View Post
    Fans staging properly?
    Are all of your sensors reading accurately?
    What's your SH/SC
    Do you have a operating Log?
    I second that check your condenser fan motors.

  4. #4
    Join Date
    Sep 2005
    Location
    Maryland
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    Quote Originally Posted by chrishvacman View Post
    Fans staging properly?
    Are all of your sensors reading accurately?
    What's your SH/SC
    Do you have a operating Log?
    I'll start with checking that this evening, I was there last week which is why I knew the charge (at that time) was good. However, I just had received emails regarding the faults it was logging, which is what prompted the question. So this could be an issue with condensing temperatures and not so much an oil restriction?

  5. #5
    Join Date
    Jun 2012
    Posts
    526
    High cond. Pres. Causes a high enough oil differential to trip it. A lot of times one fan falls out and knocks multiple fans out.

  6. #6
    Join Date
    Aug 2009
    Location
    Prattville, Alabama
    Posts
    1,749
    A search of this site will show numerous threads on this subject. This is not an oil DP switch function. It's usually caused by carry over, or over feeding refrigerant to the evaporator. Check the compressor discharge temp. And look at the temperature sensors that are used to control the EXV. That would be the saturated evaporator refrigerant temperature sensor and the compressor suction temperature sensor. And perform the test on the EXV.

  7. #7
    Join Date
    Jun 2012
    Posts
    526
    Quote Originally Posted by Nuclrchiller View Post
    A search of this site will show numerous threads on this subject. This is not an oil DP switch function. It's usually caused by carry over, or over feeding refrigerant to the evaporator. Check the compressor discharge temp. And look at the temperature sensors that are used to control the EXV. That would be the saturated evaporator refrigerant temperature sensor and the compressor suction temperature sensor. And perform the test on the EXV.
    The 125's and lower don't do what i was reffering to do they.

  8. #8
    Join Date
    Aug 2009
    Location
    Prattville, Alabama
    Posts
    1,749
    Correct, Freightshaker. It's easy to get them confused. I've done it myself. And I ain't gonna promise that I won't do it again!

  9. #9
    Join Date
    Jul 2012
    Location
    Western KY
    Posts
    1,221
    Sensors being off can cause it. Plugged oil filter could possibly cause it, holding oil in cooler. Never had this fault on the baby screws I take care of so let us know what you come up with.

  10. #10
    Join Date
    Jun 2012
    Posts
    526
    I'm good at that. Checked a manual after you said that and got to thinking about it. I don't think I have been around a RTAA under 125. Have a safe day NC.
    Keep us updated OP.

  11. #11
    Join Date
    Jul 2009
    Location
    In a mechanical room....
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    Don't forget to check the accuracy of those sensors and DO NOT check that SH and SC with readings from the panel use your own manifold and thermocouple.
    “It takes courage to grow up and turn out to be who you really are.”

    - E.E. Cummings

  12. #12
    Join Date
    Sep 2005
    Location
    Maryland
    Posts
    221
    An update will be coming in the next couple of hours. Thanks for all the advice it's pointing me in the right direction.
    I also noticed a post earlier where someone was talking about sweating LL canisters on these units possibly caused by bad EEV's. Coincidentally enough this unit does the same when not running (several hours after shutdown is when I noticed it.) So the EEV will definitely be looked at and tested once on site.

  13. #13
    Join Date
    Sep 2005
    Location
    Maryland
    Posts
    221
    Update: unit is now online, both circuits are running. Here are the readings for circuit 1 (the circuit that has been tripping on 'oil failure').
    Compressor RLA average=91%
    Entering oil temp=125* (actual reading 121*)
    Evap Pressure=68 (confirmed)
    Cond Pressure=251 (actual reading 233 at LL)
    Compressor suction temp=48* (actual reading 52*)
    Evap temp=40*
    Saturated condenser temp=117* (confirmed)

    SH: 14ish
    SC: 9ish

    Those were the readings.

    I ran an EEV test, and it appeared to operate fine, upon opening I saw refrigerant flow in the sight glass, upon closing it stopped.
    Now something odd I haven't heard before was happening, shortly after the chiller started up, on circuit 1 I was hearing a very very high pitched buzzing sound (almost not noticeable), happening for about 5 seconds every 20 seconds or so. Not sure if this info will help anyone but I couldn't pinpoint where it was coming from, just that it sounded to be coming from the two unloader solenoids on the male side?

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