Furnace Hum/Vibration

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  #1  
Old 12-15-08, 05:33 AM
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Furnace Hum/Vibration

I have a natural gas furnace that is causing a low frequency hum/vibration throughout my house. It only occurs when the smaller fan (the one that initially takes in air when starting up) is running. It gets worse when the fan is winding up and winding down but it hums/vibrates the entire time the small fan is running. Any suggestions? Thanks for your time.
 
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Old 12-15-08, 04:27 PM
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If you have the big flat blade type, they can warp. Hence, out of balance. Or they can even slip down the shaft due to corrosive exhaust acid, and the plastic fanblade then can even start hitting the plastic inducer housing.

I have been fortunate to have some HVAC acquaintences who sell me blades when they have them. But to my understanding, for most people, you have to replace the entire inducer, motor and all. I think for the last one I looked into, before jury rigging the blade on the shaft again better, they wanted about $150 for the whole thing.

Maybe someone else here can jump in and shed any light on where you might just get a new blade.
 
  #3  
Old 12-16-08, 05:37 AM
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Thanks ecman51. I need to do some checking to see what kind of motor/fan it's got (it's a Lennox Value Series). It isn't very loud when standing right in front of the furnace, but it's loud upstairs. This makes me think it is sending some kind of vibration up the main pipe. I tried to decouple the pipe from the furnace with some chimney sealer (I needed something that could withstand the heat) but it's not as "rubbery" as I'd hoped. I may try to find another product that can go between the furnace and pipe to decouple the vibration before going the new motor route. Does anyone have any ideas of a product that can take the heat but stay rubbery enough to dampen the vibration? Thanks.
 
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Old 12-16-08, 03:14 PM
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First off, have you tried to dampen anything with your hand (with protection on it if need be, for heat), to see if trying to just dampen it could work?
 
  #5  
Old 12-16-08, 07:50 PM
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Yes, if I dampen the pipe with my hand the vibration is greatly reduced. I've tried coating the joint between the pipe and the furnace with chimney sealer to decouple them, but the vibration persisted.
 
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