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  1. #1
    Join Date
    Mar 2011
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    Abilene Tx
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    82

    Trane RTAA Winding temp alarm

    Been having problems with a RTAA 100 ton chiller, two circuits. I replaced circuit B compressor about a month ago and it has been running fine until the past week. We have had 100F ambient air also for the past month down here in Texas. Circuit A is fine. On install, I weighed charge in to 100lbs. Unit calls for 98lbs but I added a suction line drier. It is a remanufactured compressor and was shipped with no oil. I follow directions and put about 2 pints in suction cavity of compressor and primed oil filter two hand pumps of oil. I also put in fresh three gallons of Trane 15 oil. I previously cleaned entire system because of burnout. After changing drier cores out multiple times I checked for acid and system was clean so I took suction drier cores out and button her up. I added two extra pounds of freon because of the extra piping. So it has been running fine for a month and that was the history of it. Now it is going off on winding temp. I have checked all condenser fans, cleaned condensers very good, checked for restrictions on LL drier all good. Got a clear sight glass, around 5-6 superheat and 18-19 subcool. I have a normal suction pressure, about 90psi with 65F water leaving. Head pressure is a little high, around 360. I cannot seem to find anything about the compressor winding stats. The cover of the panel on top of compressor shows three t-stats, I have mine hooked up from W to BT. What are the three for? Can I switch them around if maybe one is faulty? I'm open to ideas, thanks!

  2. #2
    Join Date
    Jun 2010
    Location
    Tampa, FL
    Posts
    101
    Check the submittal data for operating conditions. Normal for ac is 45 out/55 in. Looks like you have high load. Check evap water flow gpm. Motor cooling depends on about 40 - 45 suction temp. You need the SB to check out the sensors. There is one for each of the 3 phase windings. You can reduce the evap flow rate until the load is under control. If then it can't maintain design temp chiller is too small. Walk fan deck to make sure all fans blow up. One or two fans turning backward can make a big difference. Check istalllation. No walls higher than top of chiller and 6 ft clearance all around.

  3. #3
    Join Date
    Mar 2011
    Location
    Abilene Tx
    Posts
    82
    Well, of course, three stats for each winding. I should have figured! LOL The clearance of the chiller is very well, lots of room. I have checked all fan rotation and operation. That is good. I have not checked water gpm, although pressure is good. Chiller usually maintains 6F or 7Fwater ent/leaving. The chiller has a huge load. They have lots of servers/computers in the building. With Circuit A running only, and the 100+ temps we have had, the water will be 65F+. With both circuits running it pulls it down to setpoint, 45F, but struggles once it gets to 55. Also, chiller will run all night and day, water temp will be around setpoint until 4pm comes around and then circuit B compressor goes on winding temp alarm. That's what stumps me, as the load isn't high at all. Ambient temp is hot as heck, but the water temp has already been pulled down.

  4. #4
    Join Date
    Aug 2006
    Location
    Mixing oil and fire with a big spoon.
    Posts
    4,494
    you probably have an inaccurate saturated evap temperature sensor or compressor temperature sensor. i know it says 4-5F but it most likely isn't.

    check your discharge superheat...it should be around 25-35F at full load. maybe a little higher if it is unloaded.

    high suction superheat causes the windings to overheat. high discharge superheat is a great indicator of suction superheat temperature sensor accuracy. i can promise you right now that you can not accurately measure the suction superheat with a bead probe. you would need to have the access core removed and a probe installed to accurately measure it...i have a setup that allows me to do this...discharge superheat is so much easier.

    as for the 3 gallons of new oil...how much oil did you remove FIRST? you didn't just add oil without removing 3 gallons first did you?
    "If you pull one more stunt like you just pulled with Tommy, you won't have to get on a plane because I will personally kick your ass from here to Korea!" - Best of the Best

  5. #5
    Join Date
    Mar 2011
    Location
    Abilene Tx
    Posts
    82
    I completely drained the oil before adding new oil. Also blew system thouroughly with dry nitrogen since it was a burnout.

  6. #6
    Join Date
    Mar 2011
    Location
    Abilene Tx
    Posts
    82
    Well, I did some more troubleshooting last night on that chiller. Everything was leaning toward the unloaders. I found that the male unload solenoid valve wasn't de-energizing once loaded by the female unload solenoid valve. I replaced compressor module and everything is working great. Thanks for ya'lls help!

  7. #7
    Join Date
    Mar 2007
    Posts
    3,124
    I had a very similar issue with an RTAA125 where the unload solenoid on the B compressor would not de-energize once the female solenoid went into the loaded position. I also replaced the MCSP module in that case.
    "There is no greater inequality than the equal treatment of unequals."

    -Thomas Jefferson

  8. #8
    Join Date
    Aug 2006
    Location
    Mixing oil and fire with a big spoon.
    Posts
    4,494
    Quote Originally Posted by Cowpoke View Post
    Well, I did some more troubleshooting last night on that chiller. Everything was leaning toward the unloaders. I found that the male unload solenoid valve wasn't de-energizing once loaded by the female unload solenoid valve. I replaced compressor module and everything is working great. Thanks for ya'lls help!
    sure...that adds up. extended unloading (even though the chiller didn't want it) can cause higher temperatures. add in the extra load and your return refrigerant temperatures are already quite high...poof! you trip on your pudding temperature sensor.
    "If you pull one more stunt like you just pulled with Tommy, you won't have to get on a plane because I will personally kick your ass from here to Korea!" - Best of the Best

  9. #9
    Join Date
    Mar 2011
    Location
    Abilene Tx
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    82
    Quote Originally Posted by jayguy View Post
    sure...that adds up. extended unloading (even though the chiller didn't want it) can cause higher temperatures. add in the extra load and your return refrigerant temperatures are already quite high...poof! you trip on your pudding temperature sensor.
    Pudding temperature sensor? LOL There must be a story that I am missing on why you call it that!

  10. #10
    Join Date
    Mar 2011
    Location
    Abilene Tx
    Posts
    82

    Frown

    Bummer, buddy of mine says circuit B is down an winding temp again. It's got me puzzled, was working fine for a couple of days. The classic line, "It was working when I left!" Unloaders worked properly after changing MCSP module. Maybe the UCM (which talks to the MCSP) is not working right, who knows. I will check it out tuesday and see what is going on. Another tech told me a Trane tech he knows had a similar problem with winding temp alarm. He changed MCSP module and moved the winding t-stat wires from the terminals on the end, to the middle two (inside the compressor electrical housing). By doing that he bypasses the other two winding t-stats, right? I guess if he did that it's ok to do. I'll let ya'll know what's happening....meanwhile, any ideas welcome!

  11. #11
    Join Date
    Dec 2010
    Location
    Central US
    Posts
    431
    Quote Originally Posted by Cowpoke View Post
    Bummer, buddy of mine says circuit B is down an winding temp again. It's got me puzzled, was working fine for a couple of days. The classic line, "It was working when I left!" Unloaders worked properly after changing MCSP module. Maybe the UCM (which talks to the MCSP) is not working right, who knows. I will check it out tuesday and see what is going on. Another tech told me a Trane tech he knows had a similar problem with winding temp alarm. He changed MCSP module and moved the winding t-stat wires from the terminals on the end, to the middle two (inside the compressor electrical housing). By doing that he bypasses the other two winding t-stats, right? I guess if he did that it's ok to do. I'll let ya'll know what's happening....meanwhile, any ideas welcome!
    Probablly already checked but did you check for voltage drops, amp the motor at full load, and did you put a new contactor in when you changed out the screw comp. and check all wiring termination points to make sure they were all good and snug. Just some thoughts.

  12. #12
    Join Date
    Jan 2009
    Location
    Not in Iran
    Posts
    1,107
    i also had a winding temp alarm, drove me crazy for a miniute, i cleaned up the connections at the board and and at the compressor and problem went away
    no signature blast'em man blast'em
    !!!KILL THE TERRORIST!!!

  13. #13
    Join Date
    Jun 2010
    Location
    Tampa, FL
    Posts
    101
    That model did have crappy plug terminations at the board. Always having to pop the plastic caps and push in on the wires to reestablish good electrical contact. If you want to bypass the safeties as for a failed winding temp stat just add 75 ohm resistors at the board. I hope you don't let the smoke out. Instead of guessing you really need to get the SBs and determine whether its the board, wiring, or sensors or you actually do have a motor over temp condition. If its an old machine the efficiency of the condenser could be low. On other brands I have had to use a hp switch to energize unloader to keep machine on line.

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