Lennox Furnace Fan Making Noise


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Old 01-06-15, 10:04 PM
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Lennox Furnace Fan Making Noise

Hello all.

I am hoping someone can help me:

my furnace fan has started making a funny sound on start up - sort of a "wub-wub-wubwubwub" and the fan sounds to be howling/whistling through the vents (very annoying).

I made a youtube video below - any ideas? I looked at and cleaned the fan, but the fan was very clean, not dirty really.... Does the squirrel cage wear out, or get out of balance and cause this sort of sound? Or is it more likely the motor?

Here is the video:
https://www.youtube.com/watch?v=3gRnZaK0PfM

https://www.youtube.com/watch?v=3gRnZaK0PfM
 
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Old 01-06-15, 10:44 PM
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Perfect video..... good sound.

The blower is a little slow starting. You can try spinning it by hand. If it feels like it spins very freely I'd recommend changing the capacitor. The capacitor will be mounted pretty near the blower motor.

The howling/whistling can be caused by register adjustments.
 
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Old 01-08-15, 10:20 PM
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Thanks PJ!

When you say 'register adjustments' do you mean by opening up more registers? I have quite a few closed on the main floor to force more heat upstairs to equalize the temp between the main floor and the upper level.
 
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Old 01-09-15, 10:45 PM
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I replaced the capacitor, as the fan 'seems' to spin freely - eg: i give it a little push and it spins around for a bit and then stops.

The change of the capacitor did nothing to effect the speedup of the fan.... So could it be the motor, or an out of balance squirrel cage?
 
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Old 02-09-15, 09:00 PM
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Bump - any thoughts? The change of the capacitor did nothing to effect the speedup of the fan.... So could it be the motor, or an out of balance squirrel cage?
 
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Old 02-09-15, 09:10 PM
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I wouldn't be super concerned about the slow start up. On some that's just the nature of the beast. Does the fan appear to have an wobble to it as it slows down to a near stop?

With "quite a few" registers closed, you really should check the temperature of the supply & return close to the furnace & after the furnace has been running at least 5 minutes.
 
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Old 02-09-15, 09:22 PM
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Thanks for the quick reply! It's more the noise and the sound through the register, and the sound waking my light-sleeper infant twins! Don't remember it doing that before....
 
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Old 02-09-15, 10:36 PM
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It's normal for the fan to take longer to start on the lower speed taps. (heating speed)
 
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Old 02-10-15, 06:00 AM
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How long has this been going on?did it start after you closed the registers?
Geo
 
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Old 02-10-15, 12:08 PM
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What kind of noise are you concerned about? Is it the whistle or the blower start up?
 
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Old 02-16-15, 10:39 PM
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I am concerned with the slow, loud fan startup.
 
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Old 02-16-15, 10:43 PM
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Burning dust smell when fan left on

Let me start by saying the furnace is clean and there is no burning dust smell if I leave the fan off (ie only comes on when the furnace calls for heat). However if I leave the fan on 24/7, when the furnace goes into heat mode, you get the distinct burning dust smell.

My guess is running the fan 24/7 blows dust into the combustion chambers ?

I would have thought a MERV11 filter would have stopped that...

Any thoughts?
 
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Old 02-17-15, 03:03 PM
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Unless that filter is 4" thick, get rid of it. Merv 11 with a 1" filter will cause more problems than you want.
 
 

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