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  1. #1
    Join Date
    May 2005
    Posts
    15

    Trane intellipak help.

    RTU supply fan sometimes starts and sometimes not. I have a diagnostic
    "OA humidity sensor failure" I replaced the sensor but the diagnostic is still there after resetting. Upon startup the oa damper opens to 10%, unit goes to occupied mode, the K-2 relay on the RTM closes (Enableing the vfd) but no speed signal is coming out of it. After about 2-3 minutes I get "supply fan failure"

    When it does try to start, it tries to ramp up to 60hz but before it gets there it shuts down and I get a "space pressure sensor failure". Does anyone have any ideas?

    Thanks in advance


  2. #2
    Join Date
    Mar 2008
    Posts
    82
    Is the pressure sensor it is controlling to ok?

  3. #3
    Join Date
    May 2005
    Posts
    15
    It seems to be.

  4. #4
    Join Date
    Oct 2007
    Location
    Austin Texas
    Posts
    1,814
    I've got a couple of I-pacs on my roof that will still run with the diagnostic that you describe.
    Nemo me impune lacessit.

    How much blood do I have to bathe in to get clean?

    Don't look down on anyone unless you're helping them up.

  5. #5
    Join Date
    May 2005
    Posts
    15
    ok...thanks. Any idea why the supply fan wont start?

  6. #6
    Join Date
    Oct 2007
    Location
    Austin Texas
    Posts
    1,814
    I would start with the VFD.
    Nemo me impune lacessit.

    How much blood do I have to bathe in to get clean?

    Don't look down on anyone unless you're helping them up.

  7. #7
    Join Date
    Dec 2007
    Location
    chicago
    Posts
    249
    Quote Originally Posted by John Culpepper View Post
    I would start with the VFD.
    I had the same problem last year, unit under warrenty, Trane came out and replaced the vfd. Trane VFD has a tech support # 1-877-872-6363

  8. #8
    Join Date
    Oct 2007
    Location
    Southern Indiana
    Posts
    94
    Check the pressure switch in front of the fan. Its down by the motor mounted on the panel to the right of it. It's the supply fan proving switch I have changed a few of those. If I remember correctly it had the same symptoms you are describing.

  9. #9
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    19,261
    Quote Originally Posted by GOVHVAC View Post
    Check the pressure switch in front of the fan. Its down by the motor mounted on the panel to the right of it. It's the supply fan proving switch I have changed a few of those. If I remember correctly it had the same symptoms you are describing.

    During the summer of '08 I found a bad crimp on one of the two wires that connect to the pressure switch. I found it when I placed my hand on the connector and pulled it off the spade terminal and the wire popped out of the end of the connector. It had been crimped onto the insulation, and not the wire conductor.

    I also pulled a panel (with door and hinge assy) to reach it more easily.
    [Avatar photo from a Florida training accident. Everyone walked away.]
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  10. #10
    Join Date
    Nov 2005
    Posts
    1,350
    I doubt the supply air dp switch controls the vfd. I have had supply air proving switch failures and it has always been the switch or a dead fan motor. I would suspect that the vfd is the issue and the proving switch is doing its job.

    Space pressure sensor fault? I have not seen that before. Find the space pressure sensor and verify that it is operating correctly.
    I STARTED WITH NOTHING, AND I STILL HAVE MOST OF IT!

  11. #11
    Join Date
    Jan 2004
    Posts
    1,176
    They have service mode for trouble shooting.
    Federal Reserve, stealing your kids futures since 1913

    UA290

  12. #12
    Join Date
    Jun 2004
    Location
    Milwaukee, WI
    Posts
    258
    Trane I paks supply fan will start with a 0% single to the VFD. A start command will be sent and then the UCM controller looks for a closed pressure switch within 1200- 180 seconds. If no proof made the unit will shut down . There is typically a couple pressure transducers in the fan cabinet. Duct static, Building Static, High Static Safety. Check tubing and terminators for obstructions and breakages. 0-5 vdc signal from transmitters.
    Jeff F.
    www.vfdhelp.com
    VFD, HVAC Motors and Manufacture Assistance.

  13. #13
    Join Date
    Nov 2009
    Location
    Aptos, Ca
    Posts
    40
    Check the K-42 relay in the vfd compartment for proper operation. Terminal 12 on vfd is 24Vdc out. see that you also have 24vdc at terminal 18 and 27 when you start the unit, these are the interlocks. Terminal 53 is the 0-10 or 2-10Vdc drive speed command. Minimum speed should be 22hz. Also as mentioned below, in the filter access compartment above the economizer motor and exhaust damper motor are the transducers for space pressure and static pressure. Check and make sure the pnuematic tubing is proerly attached and not backwards also check the wiring plugs. Of course run the unit in test mode and then use the status menu to see if you are building supply air static and any measurable building static. Also in the supply air section next to the fan discharge is the supply fan proving switch and the static pressure pick-up cone. I have seen those tubes rub holes in each other. Check the plug on the econo module in the control panel that receives the building static input. Its also possible you have a failed module.

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