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  1. #1
    Join Date
    Feb 2009
    Location
    philly area
    Posts
    5

    Carrier 30gt-100-chiller EXV problem

    Troubleshooting output voltage on the procesor board for ckt.a EXV. The IOM says to set voltmeter to 20 vdc and check output voltage to valve where the wire plugs in. (on the processor board) I am getting a floating voltage between 1 and 3.9 vdc. Does that seem correct? Checking when machine control power is first energized as per IOM.

  2. #2
    Join Date
    Jan 2007
    Location
    central america
    Posts
    157

  3. #3
    Correct. If voltages does not fluctuate or stays at zero check processor.
    If voltage fluctuate then ohm check exv then open up exv and check to see if orfice is scared or will not slide easily.

  4. #4
    Join Date
    Mar 2007
    Location
    State of Confusion
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    1,210
    Not to throw a wrench into the works here but I believe you could change the exv to a txv and then change the operation in the config menu....If all else fails why not go that route?

  5. #5
    Join Date
    Feb 2009
    Location
    philly area
    Posts
    5
    Thanks for the responses. The IOM manual shows the specifics on EXV troubleshooting. I am at the point where I am going to pull the valve apart. I just was just looking for the specific output voltages coming out of the processor. Ckt. b is disabled due to lack of load. If 1 to 3.9 vdc is sufficient then I am happy with it. I will probably be going back to the job mon. or tuesday this coming week. Thanks for the link for the manual.

  6. #6
    Join Date
    Jun 2004
    Posts
    26
    Maxpower is absolutley right. Put in a txv. Done it a few times-no more problems

  7. #7
    Join Date
    Mar 2007
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    State of Confusion
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    1,210
    Superheat is Superheat. Screw the electronics..

  8. #8
    Join Date
    Jan 2008
    Location
    Dallas ,Texas
    Posts
    3,710
    Not to forget about the obvious but are your sensors ok? Return gas and saturated suction temp.
    UA 100

    It takes three people to do anything around here. Two do the work, one explains to the crowd of people who showed up when they seen smoke and flames.

  9. #9
    yes voltages will fluctuate from o to 3.9 vdc. exv's produce a tighter control and improves efficiency. But whatever.

  10. #10
    Join Date
    Feb 2009
    Posts
    52
    philly420,

    First what is the error code you are getting for the 30GT? And need some info to assist.

    - Most common problems for the EXV on this Chiller is sensor failures for either T-5 Evaporator or T-7 Compressor sensors assuming it is circuit-A, read dc voltage for both and compare to temps and you will usually find one sensor reading incorrect, the most common is evap sensor.

    -To check the EXV set meter 20vdc and cycle control power and measure voltage of proccessor board, as the chiller will step the EXV, one lead is on common and the other on the output and you will see a rise and voltage and then drop to zero as it goes to the next output on the winding (happens quick)

    - You can also cycle control power and put your hand on the EXV and feel it pulsate the valve open and closed.

    -If the sensors check out for DC Volts and temps are correct, ohm out the winding on the EXV from com to the others, if any (one) are open you need a new EXV as it will not adjust superheat correctly during the load and either have to low/high superheat and fault.

    We service hundreds of the Carrier Chiller products, never converted to a TXV for any problem either, the machine is a a little sensative but a pretty good product, just follow the service tech book posted.

    More often than not just one of the sensors.

    Paul R.

  11. #11
    Join Date
    Feb 2009
    Location
    philly area
    Posts
    5
    Thanks for all the info. Checking the sensors was on the agenda. I will be going back probably early this week. (chilled water has a economizer switchover) I will let you guys know what I come up with.

  12. #12
    Join Date
    Feb 2009
    Location
    philly area
    Posts
    5
    Today I checked the sensors associated with EXV Ckt. A (t5 & t7) The sensor at the compressor checked out ok. The sensor at the barrel was off 6 or 7 degrees colder. I figure I will probably replace the barrel sensor. I also felt the EXV motors to see if I felt movement and I did. I am not sure if a 6 degree diff. on temp on the sensor would cause the valve to stay clolsed or not but I am thinking maybe it could due to it thinking the evap is colder than it is. I will prob. replace the sensor and run it and check before I open up the system. Any thoughts? p.s. My method of checking the sensors was with ice and water w/thermometer reading a steady 32.

  13. #13
    Join Date
    Feb 2009
    Posts
    52
    philly 420

    What error code do you get for the lockout? The way you checked them is fine, but a lot of work pumping down and pulling the, for the evap sensor just run the unit and note the suction pressure and convert to temperature from a P&T Chart, the comp sensor I pull and compare to ambient when I have too, and of course isolate and pump down the entire circuit.

    There is another book from Carrier called 30GT Controls and Troubleshooting that has a lot more detail for servicing the unit, as oppose to the Installation and Strart-Up one posted above.

    Paul R.

    That error is enough to cause lockouts for the superheat on the machine and I would change it,

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