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  1. #1
    Join Date
    Jun 2005
    Location
    Henrico,VA
    Posts
    69

    Trane TCD Cond Fan Fuses Blowing

    My newly aquired customer has 4 of these package rooftop units,
    Mod#TCD600AD0C2BBNF4DH
    The 20 amp condenser fan fuses blow from time to time.I first
    saw it happen this summer.
    The motors ohm out good and draw
    about 6 amps.Two (208vac/1 phase) motors per 20 amp fuse
    (one 20 amp fuse per line)
    I had another call on one of these yesterday where all 4 fuses were blown(all 4 fans offline).Replaced the fuses after checkingfor grounds,open windings and bad run capacitors.Motors came online without a hitch.
    A.B.C.-always be careful!

  2. #2
    Join Date
    Feb 2010
    Location
    Landis North Carolina
    Posts
    528

    Thumbs up

    Quote Originally Posted by rgd2005 View Post
    My newly aquired customer has 4 of these package rooftop units,
    Mod#TCD600AD0C2BBNF4DH
    The 20 amp condenser fan fuses blow from time to time.I first
    saw it happen this summer.
    The motors ohm out good and draw
    about 6 amps.Two (208vac/1 phase) motors per 20 amp fuse
    (one 20 amp fuse per line)
    I had another call on one of these yesterday where all 4 fuses were blown(all 4 fans offline).Replaced the fuses after checkingfor grounds,open windings and bad run capacitors.Motors came online without a hitch.
    Did you check start-up amps, are fans staged, are the fans not running spinning bacwards before start-up? Also check wiring, loose connectors ect. are bearings worn? can you pull or push on shaft and feel resistance? Ive had motors run fine untill a load is put on such as pulling/pushing effect of fan. check to see if any are turning backwards/is it 3ph? maybe someone replaced fan motor and didnt check rotation,also if not 3ph check caps. and wiring to them for misswiring.

  3. #3
    Join Date
    Jun 2005
    Location
    Henrico,VA
    Posts
    69
    I did check starting amps,voltage capacitors,wiring for shorts or miswiring.Nothing like these seems to surface.These motors are single phase and wired from the factory to run in the correct rotation.
    They seem to have enough torque to change from deenergized
    (turning backwards)to correct rotation when energized.
    The fuse blowing problem seems to appear on all 4 rooftop units at various times.
    The customer has been told that the electrical service to his building is bad at certain times.If that is the case,I would like to have some type of fix.
    I will at some point go back and recheck everything you mentioned although,gut feeling is that something else is happening.
    Thanks for the reply.
    A.B.C.-always be careful!

  4. #4
    Join Date
    Oct 2001
    Posts
    6,945
    counter rotation from the lead fan then the other kick in?just for future reference...on the supply fan side and 460 rooftops trane was short on the wires from the contactors to what the motors had so you'll see a line voltage terminal strip looking into the fan belt section at the 2 o'clock positon mounted on the fan shroud.over the years belt dust moisture and fan vibration cause arking on the slip connectors and as soon as you close the fan contactor with the access panel down baa boom you think the motor blew it was the 3 phase terminal jumping on each other remove the sta-kons and wire nut it and wire tie it onto the shroud check the fan contactors thy take the hit also...CFM are rotation in off position
    "when in doubt...jump it out" http://www.youtube.com/watch?v=U1qEZHhJubY

  5. #5
    Join Date
    Jun 2005
    Location
    Henrico,VA
    Posts
    69
    counter rotation from the lead fan then the other kick in?
    I am going to have a closer look at the counter rotation situation,stickinit2thman mentioned that also.
    Thanks for the heads up on the indoor fan.
    A.B.C.-always be careful!

  6. #6
    Join Date
    Nov 2010
    Posts
    10
    I had that problem before. Almost every week the fuse blow.
    Check temp on the fuses using infared thermometer, line side and load side if there is difference in temp change the fuse holder.

  7. #7
    Join Date
    Feb 2010
    Location
    Landis North Carolina
    Posts
    528
    Quote Originally Posted by rgd2005 View Post
    My newly aquired customer has 4 of these package rooftop units,
    Mod#TCD600AD0C2BBNF4DH
    The 20 amp condenser fan fuses blow from time to time.I first
    saw it happen this summer.
    The motors ohm out good and draw
    about 6 amps.Two (208vac/1 phase) motors per 20 amp fuse
    (one 20 amp fuse per line)
    I had another call on one of these yesterday where all 4 fuses were blown(all 4 fans offline).Replaced the fuses after checkingfor grounds,open windings and bad run capacitors.Motors came online without a hitch.
    Fuses should be time delay or HACR rated to allow for starting of motors.

  8. #8
    Join Date
    Feb 2010
    Location
    Landis North Carolina
    Posts
    528
    Quote Originally Posted by stickinit2thman View Post
    Fuses should be time delay or HACR rated to allow for starting of motors.
    This may be reaching a bit but is there any kind of weired airflow such as conditions that make downdraft condition and fans are turning rapidly backwards before start-up at certain times and are the units competing for air from other units? Check contactors for proper voltage accross terminals.

  9. #9
    Join Date
    Oct 2011
    Location
    MASON NECK VA
    Posts
    17
    Just as an easy way if the customer said the power is dirty install a ICM digitial Phase monitor on the line side of the power inside the unit to see phase problems. I had the same problem and after checking all the above notes in the responce found on leg would drop/brown for a few seconds causing high amp and fuse loss.

  10. #10
    Join Date
    Jun 2005
    Location
    Henrico,VA
    Posts
    69
    Brokanic,good point.The fuses have been replaced so may times,
    the tension on them may be getting slack.

    stickinit2thman,The 20 amp fuses are time delay.I am still waiting on a chance to get back to this job.I am trying to figure
    out how to replicate all four fans turning backwards and then
    all of them getting powered.The motor repair shop we use has a neat little gadget that can be installed on motor to prevent the backward motion.A little pricey though.

    The backwards motion fans is not new to me.I have seen them continue to run backwards when power is applied.

    SAILFISH,The units do have the ICM addon phase monitors.It was late the other day when I got the call,but I believe I glanced at it and no faults were indicated.Oh,and welcome to the forums.
    A.B.C.-always be careful!

  11. #11
    Join Date
    Mar 2010
    Location
    central us
    Posts
    32
    sounds like the building is having power surges

  12. #12
    Join Date
    Apr 2007
    Location
    Saint Augustine, Florida, United States
    Posts
    1,152
    low voltage, higher amps. fuses blow. brown outs....could it be that simple? data log their voltage?

  13. #13
    Join Date
    Jun 2005
    Location
    Henrico,VA
    Posts
    69
    data log their voltage?

    Good idea,thanks
    A.B.C.-always be careful!

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