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  1. #1
    Join Date
    Aug 2002
    Location
    NTexas
    Posts
    79

    Trane YHC blower overamping question??

    Hey guys,

    Got a quick problem and looking for some feedback

    Got a guy out in the field doing an air balance and trying to troubleshoot an overamping blower motor. He's fairly green so I'm having to walk him through everything. Running out of ideas here, and looking for that one thing I haven't thought of.

    Here's the details.

    Trane YHC092A4RMA
    480 v (495 actual)
    2 hp blower motor (3.1 FLA / 3.6 SFA)

    Initial airflow was measured at 136% of Engineers design airflow. (3000 cfm) (we find this a lot, so it's not unusual)
    Motor initially operating at 4.1 amps (FLA = 3.1)
    Tech adjusted pulley to minimum setting. This brought airflow to 125% of design, but amps only went down to 3.9.
    Replaced blower pulley and brought airflow down to 100% of design, but amps only went down to 3.7.
    RPM and pulley sizes are consistent with what we see on this concept, but the motor staying above FLA is not. No matter how far he slows the fan down, the amps are not dropping more than a 10th or two and the fan remains above FLA. Motor is not excessively hot.

    This is the details of one system. There is also an 8.5 ton unit with the same problem. The motor will not go below FLA despite any adjustments. The remaining 4 units are all okay.

    Right now he's checking for a short cycling roof curb.

    I can provide any additional details if you need any.

    Thanks,

  2. #2
    Join Date
    Mar 2003
    Location
    Cincinnati
    Posts
    7,977
    Hope this don't sound too elementery but if it's a belt drive blower he don't have the belt too tight does he ??

  3. #3
    Join Date
    Aug 2002
    Location
    NTexas
    Posts
    79
    That's where I'm at with it. I'm overthinking it now and possibly overlooking the obvious.

    At this point nothing is too elementary. I'm open to any possibilities.

    He's running a static profile for me right now.

    Thanks, Mattm

  4. #4
    Join Date
    Mar 2003
    Posts
    7,326
    how about running a voltage check? sounds like the building voltage may be a bit low if all units are overamping....

  5. #5
    Join Date
    Aug 2002
    Location
    NTexas
    Posts
    79
    Quote Originally Posted by flange View Post
    how about running a voltage check? sounds like the building voltage may be a bit low if all units are overamping....
    Only 2 of 6 units are overamping.

    Supply is 498 volts. 286/287/283



    ESP is .61 on the 8.5 ton @ 894 rpm =3800cfm
    ESP is .52 on the 7.5 ton @ 700 rpm =2800cfm

  6. #6
    Join Date
    Dec 2003
    Location
    45th Parallel
    Posts
    957
    I am a little out of my element here, but, I assume all duct work is done?
    Does your ESP seem a little low?
    I guess you got the airside under conrol, so maybe you have a motor problem. Are all legs balanced? T1, T2, T3.
    What is the amp draw unloaded, with belt off? How does it compare to the other fans of same HP(that don't have this issue)
    with their belts off? Maybe you have a motor with electrical center off causing it to pull higher amps. Most of the new stuff is made in Mexico or China anymore, so you never know.

  7. #7
    Join Date
    Jun 2007
    Location
    Darby, PA
    Posts
    561
    A bit off center, but where are you getting motor info? From unit nameplate or motor nameplate? Is it possible that motor may be different than unit nameplate, such as a larger HP motor?
    Psalm 51:10, 12

  8. #8
    Join Date
    Aug 2008
    Location
    Michigan
    Posts
    27
    My guess would be the fan is pumping the air (short curcuit in roof curb) or the motor is bad. Take the belt off and check amps of motor.

  9. #9
    Join Date
    Aug 2002
    Location
    NTexas
    Posts
    79
    Tech left the site. Had to get home (6 hrs) to spend time with his girlfriend. That's another issue we'll be discussing tomorrow. Looks like I'm going out to Vegas next week to do a quality audit on this guy and take over troubleshooting these units with the installing contractor. Aaargh!!! I hate flying anymore. Hopefully they can figure it out before then.

    Motor info is off motor plate. Static pressure is right on according to Tranes fan curves, which is confusing me even more.

    Once I can get in front of it, I'll figure it out......but keep the ideas comin' anyway wink wink

    One thing I didn't have him do was belt off amp draw.

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