New blower motor shakes

Discussion in 'HVAC Heating & Cooling' started by giwatcher, Mar 6, 2021.

  1. giwatcher

    giwatcher New Member

    Joined:
    Dec 19, 2011
    Location:
    tn
    Hello:

    I am hoping for repair advice on my gas package unit, PGAA60E1KG. It is old enough that when I needed to change the 230v blower motor 1 year ago, including a new cap, I was not surprised. The repair seemed uneventful. Now, 1 year later, I smelled oil in the vents. I inspected outside and the motor was noisy and vibrating the whole unit. The strap and mounting bracket were tight, the bushings on the bracket seemed fine, and there was grease at the base of the motor shaft. The blower wheel had 2 weights on the blades, no gaps to suggest a weight dropped off. There had been no damage to the blower wheel that would make it unbalanced.

    This was a pricy OE direct replacement motor. Next day, the motor froze and there was an electrical pop.

    The motor windings were black, the terminals were all shorted to the case/ground, and the control board was burned at the fan relay. I installed a new direct replacement motor, same cap, 1 year old, tested in range, 20.6 mf, with no short to the case, and a control board.

    Everything runs as it should, but the motor vibrates like when it failed. I can't find anything loose or wobbly.

    It is a 6 amp motor, 230v, line in 246v, and pulls 5 amps while running. Is it ok to run at 5 amps? I thought it would run at 2 amps or so. Surely I don’t have a bad new motor?
    Did the vibration or out of balance condition burn the motor? Will it burn up the new motor if I use it?
    Can a blower wheel get out of round for no reason, if it looks like there are no missing weights?
    Any thoughts on what might be the problem, since I can't find anything loose or wobbly. ?
     
  2. fitter30

    fitter30 Well-Known Member

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    Retired service tech
    Location:
    Peace valley missouri
    Blower wheels can fail in different ways can throw a weight and might just leave a scratch on the blade, wheel start to oval ,hub come loose from wheel and blade come loose wheel doesn't spin true. Normally manufacturers wouldn't use a 6 amp motor running 2 amps. Oem motors rate their amp draw a little different from a aftermarket. They might rate 1/2 hp @ 6.1 amps and a aftermarket 6.0 amps. When ever using a aftermarket never pick a motor by hp has to be by amp draw and even if it's .1 amp less pick the next size motor. Oem blower wheels normally just a little diameter and or width than aftermarket.
     
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  4. WorthFlorida

    WorthFlorida The wife is still training me.

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    Orlando, Florida
    Most new motors have sealed bearings and they could be sleeve, roller or ball bearing. Since you smelled oil, might be grease, at least one bearing failed. One may have worn out and now there is play causing it to wobble. It sounds to me a bad motor from your descriptions.

    Your timeline of events is confusing? At least to me.
    • The motor seizing was the old motor?
    • The last sentence? motor vibrates like when it failed. What failure?
    • The black motor windings; Was that the old motor or the new one?
    • The next day the motor seized; that was after replacing the motor?

     
  5. giwatcher

    giwatcher New Member

    Joined:
    Dec 19, 2011
    Location:
    tn
    Sorry, WorthFlorida, for the confusion. I will try to clarify.
    One year ago, 2/6/20, a 20 yo original blower motor failed due to age. I replaced it and no issues, no vibration.
    Now, the one year old replacement motor was creating an oil smell in the vents, 2/7/21. I found it running but lots of new vibration shaking the whole unit.
    This replacement motor, a day later, 2/8/21, failed. It burned the winding, shorted to ground, and took out the control board.
    I just now, 3/6/21. replaced this 1 yo motor with an oe direct replacement and replaced the control board. Unit now runs, but with the same extreme vibration that appears to be the cause of burning out the motor I replaced 1 year ago.
    The current motor and board are new, but I am not using, because I believe the vibration is what destroyed the 1 yo motor. There is no play in the shaft of the motor I just installed, it is brand new.
    Again, I can't find loose spline or missing weights on the blower wheel. I can't find any loose hardware, mounting strap, bracket that seems loose to cause the vibration/wobble.

    Although everything runs as it should now, the motor vibrates like when the 1 yo replacement motor failed, 2/8/21. I can't find anything loose or wobbly.

    It is a 6 amp motor, 230v, line in 246v, and pulls 5 amps while running. The label says 6 amps and does not provide full load or run load amps. Is it ok to run at 5 amps? I thought it would peak at 5 amps and run at less, maybe 2 amps or so. Surely I don’t have a bad new motor? There is no play in the shaft of the just replaced new motor.
    Did the vibration or out of balance condition burn the 1 yo old replacement motor? Will it burn up the new motor if I use it?
    Can a blower wheel get out of round for no reason, if it looks like there are no missing weights?
    Any thoughts on what might be the problem, since I can't find anything loose or wobbly ?
     
  6. WorthFlorida

    WorthFlorida The wife is still training me.

    Joined:
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    Occupation:
    Retired
    Location:
    Orlando, Florida
    Electrically, check the circuit breaker inside the panel. Remove the cover and check the wires going to the 240 volt breaker. The wires at the breaker should not show any burning or melting of the insulation. Check that the screws are tight. Don't over do it, you can strip the screws. If the blower motor has been running for a while place your finger on the top,side of the breaker to feel if it is hot. The most it might feel warm at near the breaker rating on current draw, but it should be at ambient temperature. 240 volt motors can burnout if one leg is lost. The motor that lasted a day, did it have an option for 120v or 220v operation? Motors that are both will usually be factory strapped for 220v. Really not sure why the control board burned. If it has a 220 volt transformer on it, when the motor burned may have lost one leg for a few moments and burned out the transformer.

    I would not worry about the current draw. You are under the plate reading. AC motor current draw depends on load and input voltage. If the load is too great and it slows the rpm down, the motor will draw more current. Higher the line voltage the motor will draw less. I'm not sure on blower motors but pump motors and compressor motors have a built in thermo switch. If the motor over draws current, the thermo switch trips out to save the motor.

    Vibration alone cannot burn out a motor. This might be a hassle but remove the blower wheel and run the motor in the housing if possible. If the motor runs smooth then the blower wheel is out of balance. Why? Who knows. After twenty years there is usually dust build up on the squirrel cage fins and until you scrape a screw driver on them it might look like they are clean.

    I recently burned out a pool motor after replacing the starter cap and was at my son's house. When I replaced the cap I didn't run one wire from the cap correctly. The centrifugal switch was hitting this wire and after a day or two the wire finally cut through and the motor fried. $200 later I replace the motor. Sometimes $hit happens, don't we know.
     
    Last edited: Mar 7, 2021
  7. Bannerman

    Bannerman Well-Known Member

    Joined:
    Mar 19, 2014
    Location:
    Ontario, Canada
    Assuming this is not a belt drive blower, is the blower squirrel cage supported on the opposite side from the motor shaft connection? A belt drive blower would use 2 bearings, one on each side whereas a direct drive could utilize 1 bearing. If there is a support bearing, check the blower shaft freeplay as a support bearing maybe too worn and allowing movement or placing additional load on the motor.

    A 'G' search for that model number does not locate any info. Ensure the motor is actually being fed 230+ volts as a blower will often run on 120 volts. If the motor is 115/230 volt capable, perhaps it is being fed 120 volts to the 230 volt terminals.
     
  8. fitter30

    fitter30 Well-Known Member

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    Location:
    Peace valley missouri
    Replace the wheel ,motor amps should be listed on unit tag
     
  9. giwatcher

    giwatcher New Member

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    Dec 19, 2011
    Location:
    tn
    Thanks all. The suggestion to remove the blower wheel and reinstall everything else was brilliant! I did that using exist mounting hardware, and it runs smooth, and at startup peaks at 4 amps and immediately drops to 2.6 amps, more to my liking. However, isn't it possible that the weight of the blower wheel puts torque on the mounting strap and bushings and then creates a vibration that does not show with an unloaded shaft? Also, isn't it possible that the amp draw is 5 amps when weighted down by a blower wheel vibrating, but lower when there is less strain on the shaft?
    If you missed this in my op, It is a 6 amp motor, 230v, line in 246v. No burned wires at panel or elsewhere.
    Also, the motor did not fail in 1 day, it failed the day after I noticed the oil smell, which was 1 year after the first uneventful motor replacement.
    And, the motor is direct drive, no support opposite to the motor housing or shaft.
    So, bottom line, if the blower is out of balance, why so? No loose splines, no gaps where a weight is missing. Never been mishandled or dropped. And it didn't vibrate for a year after the first motor replacement. Yes, its dirty, but not filthy. Is unequal dirt on the blades/splines really a valid explanation?
     
  10. WorthFlorida

    WorthFlorida The wife is still training me.

    Joined:
    Oct 28, 2009
    Occupation:
    Retired
    Location:
    Orlando, Florida
    Maybe the bushings have harden if they are neoprene. I don't think anyone can say for sure why the vibration occurred. As you stated maybe the torque puts strain on the brackets and the noise from the motor transfers to the housing, like a drum?

    As I stated before, AC motors draw current depending on the load. The 6 amp is the maximum current. It's the same as the engine in your vehicle, a 200 hp rated engine is the maximum it can develop. Once you get going you it may only be putting out 75 hp.
     
  11. giwatcher

    giwatcher New Member

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    Dec 19, 2011
    Location:
    tn
     
  12. giwatcher

    giwatcher New Member

    Joined:
    Dec 19, 2011
    Location:
    tn
    Replaced blower wheel, vibration gone. I guess the original blower wheel warped from age, heat, stop/start, etc in a way that is not visible. I even check the center of the wheel where the motor shaft sits. No play that I can tell. I guess it has bearings that could allow wobble under high torq?
    I didn't know this could happen or I would have replaced the wheel when I did the first motor replacement 1 yr ago on the 20 yo unit. Thanks for the advice.
     
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