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Thread: ECM motors

  1. #1
    Join Date
    Feb 2005
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    344
    I have a curious problem with an ECM motor on a gas furnace. On start this motor will rock as much as a quarter turn in each diredtion, maybe even stop for a moment, and the finally take off. This whole process may take about ten seconds at the most. All the time this is happening, the motor acts like it is bucking or fighting itself and is making a low frequency rumble.

    The motor acts the same way even with the ECM tester from the OEM.

    Has anyone seen this before? What is the fix?


    Thanks

  2. #2
    Join Date
    Apr 2004
    Posts
    7,680
    ECM rocking is normal. If its excessive you may have a module PWM issue or a motor with one of the stator poles out of whack. Remember, on a 115v ECM, your module's capacitors do not charge as fast or as hard as they do on a 220v air handler.

  3. #3
    Join Date
    Mar 2005
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    Suppy NC
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    as doc said
    he beat me by 2 saconds lol

  4. #4
    Join Date
    Apr 2004
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    7,680
    Just curious... Was the complaint that motor rocked, like they had a problem with the noise or just something you noticed while troubleshooting or installing something?

  5. #5
    Join Date
    Feb 2005
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    344
    The motor rumbles to the point that the homeowner is becoming very annoyed. I have seen these motors run before, but, I have never seen this.

    Naturally,the rumble travels through the duct to the living spaces. The lady of the house is not at all happy when she is awakened in the middle of the night with this noise.

    The remarkable fact is that I have a second identical furnace doing the same thing and the serial numbers are consecutive.

    I have two of these installed at the shop and never hear them during a start.

  6. #6
    Join Date
    Mar 2005
    Location
    Suppy NC
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    is there a mounting bracket screw that has not been removed
    have come accross a lot where the insallers havent and the motor can cause a vibrating noise

  7. #7
    Join Date
    Feb 2005
    Posts
    344
    I have replaced the module, then the motor. The motor seems to act the same way. And I have used different 2 different ECM testers.

    These are 1hp motors. I am used to seeing the .5 hp motors run. Is it possible that the 1hp motor is rougher starting than the .5hp?

    All I know is the .5hp starts with a few rocks and a little vibration.

    GE observed the starting and said this was excesswive and it probably the module.

    Any ideas?


  8. #8
    Join Date
    Feb 2005
    Posts
    344
    Hey guys,

    After putting this blower assembly on the bench and duplicating the problem, I have tried every combination of motors snd modules you can have with 2 motors and 3 modules.

    Yes, they are all the same motors and modules. I'm beginning to think I am trying to judge the starting behavior on the way a half hp motor starts. These are one hp motors.

    I am beginning to suspect the mounts and isolators. We'll see.

    Thanks for your input.

  9. #9
    Join Date
    Mar 2005
    Location
    Suppy NC
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    4,516
    if you want to minamumize the sound of the motoe starting up i would recomend half inche liner in the return shoe and drop
    as far as redesigning the motor it is up to you
    they all rock and make a little noise. have yet to hear any complaints on the noise

  10. #10
    Join Date
    Mar 2002
    Location
    Richmond, Virginia
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    4,264
    And canvas connectors. Her ear must be very close to that motor. I've never heard one start in the living space. I do hear that familiar bumping in my sleep sometimes though.
    There is nothing more frightful than ignorance in action....Mark Twain

  11. #11
    Join Date
    Mar 2005
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    Suppy NC
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    HVAC Pro
    that may not be the motor heheheheh

  12. #12
    Join Date
    Mar 2002
    Location
    Richmond, Virginia
    Posts
    4,264
    Originally posted by tinknocker service tech
    HVAC Pro
    that may not be the motor heheheheh
    Woohooo!! I hate it when things don't wake me up
    There is nothing more frightful than ignorance in action....Mark Twain

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