Pulsation in blower motor


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Old 09-26-09, 08:10 PM
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Pulsation in blower motor

I'm down to (hopefully) my last issue with my boiler, which I'd like to try to solve. After all this I'm going to have my tech come in and double check everything and do combustion analysis and make sure all the settings are correct on the system.

I have a pulsation in the burner which is being transmitted to the framing of the house and creating a nasty sympathetic harmonic upstairs.

The pulsation is not flame related at all. In fact, when the flame is on the pulsation is actually dampened a bit. During valve delay (pre-firing) and during post-blower delay is when I can really feel and hear this pulsation.

For example, after a firing cycle the primary is set to run the blower motor for 30 seconds. No flame, just 30 seconds of blower. If I put my hand on the blower motor I can really feel it pulsating at about 4Hz.

Does this mean my motor is on it's way out? Or the squirrel cage fan is out of balance?

Anyone experience this type of issue before?

Thanks...
 
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Old 09-27-09, 09:05 AM
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It sounds like a bad bearing. The pulsation has to be causing a vibration. Put you hand on the side of the motor. Try to find where the vibration is the strongest. When it's not running, spin the cage by hand. See if it spins evenly or if it binds.
 
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Old 09-28-09, 08:51 AM
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Thanks...I checked it out and I think this was caused when I removed and reinstalled the oil pump (I was installing a fuel cut off solenoid). I think the pump was offset a little from its original mount location.

So I loosened the screws on both the pump and the motor and I spun everything and tightened back down. Pulsation is almost gone now.
 
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Old 09-28-09, 10:29 AM
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Glad to hear it.
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