1. Attention: We have put together a thread with tips and a tutorial video to help with using the new software. Please take a moment to check out the thread here: Trapshooters.com Tutorial & Help Video.
    Dismiss Notice

O/T Furnace Fan Out of Balance?

Discussion in 'Uncategorized Threads' started by timb99, Oct 26, 2008.

Thread Status:
Not open for further replies.
  1. timb99

    timb99 Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    7,332
    Location:
    Shawnee, Kansas, USA
    OK HVAC gurus.

    I have an older (circa 1986) high efficiency furnace that rattles. It's rattled for a long time, but seems to be getting worse.

    This morning I opened the fan compartment and put my hand on the fan, and it feels like the fan is out of balance.

    Anything I can do? Can the fan be removed and rebalanced?

    Tim
     
  2. Big Dave

    Big Dave Member

    Joined:
    Jan 29, 1998
    Messages:
    990
    First step would be to remove the fan from the furnace and clean it well. An accumulation of dirt in the blade cups, will affect balance. If it is a direct drive make sure the fan is tight on the motor shaft, belt drive check the belt for wear or cracking. In both cases make sure all the mounts are tight and in good condition.
     
  3. UP Gander

    UP Gander TS Member

    Joined:
    Mar 15, 2008
    Messages:
    7
    High efficiency furnaces usually have two blowers. One which circulates the heated air into the home and one which is the exhaust blower. The air circulating blower is a squirrel cage type and the exhaust blower is usually an impellor type, kind of a disc shaped affair which as it wears is prone to rattling against its housing. The exhaust blower starts before the burners are ignited and the air cirrculating blower starts after the air is heated. Does the rattling start before the burners are ignited? If so your problem may be with the exhaust blower not the squirrel cage blower.
     
  4. timb99

    timb99 Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    7,332
    Location:
    Shawnee, Kansas, USA
    Its the squirrel cage fan (that circulates the air in the house.)

    Mr. Charles, when the fan was running, and I held my hand on the fan housing, it was vibrating. Indeed, after the burners have shut off, and the fan is still running (before the air temperature has dropped to the limit switch setting) the whole furnace shakes and shimmys.

    I wouldn't expect something as low tech as this fan to be terribly smooth, but this is a pretty obvious vibration.

    It is a direct drive unit (the motor is nested inside the fan housing.)

    I'll try to figure out how to pull the fan and I'll check it for obvious dirt in the blades.

    If the blades are clean, how difficult is it to replace motor bearings?
     
  5. bocephus

    bocephus Member

    Joined:
    Jan 29, 1998
    Messages:
    527
    From: timb99
    Email:
    Date: Sun, Oct 26, 2008 - 08:29 PM ET

    It is a direct drive unit (the motor is nested inside the fan housing.)

    From: MIA
    Email:
    Date: Sun, Oct 26, 2008 - 10:02 PM ET
    Website Address:

    Two to one it needs a new belt.

    hmmmmmm?
     
  6. The Rock

    The Rock Active Member

    Joined:
    Jan 29, 1998
    Messages:
    1,491
    The nuts that hold the fan in place to the furnace loosened and it made that out of balance sound that got worse.

    Check to make sure the blower is not loose.

    Rock

    Jim
     
  7. Ljutic111

    Ljutic111 TS Member

    Joined:
    Jan 20, 2008
    Messages:
    1,730
    I installed a humidifier in a furnace a few years back and noticed a terrible vibration in the motor . I asked the daughter who stayed home if this just started and she said no , it`s been that way since they bought the house !!! Having a couple of minutes to spare , I looked into the blower and found a sandwich wrapper stuck to one side of the squirrel cage blower and removed it and asked her how that sounded ?? She said for me to turn the furnace on ?? Needless to say this bank president wasn`t the brightest star in the neighborhood . That paper was in there from the building of the house and he never questioned it for 6-7 years . Must have been miserable trying to sleep at night -- thats how bad it sounded . The guy never even called me to thank me for what I did for them !!!
     
  8. timb99

    timb99 Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    7,332
    Location:
    Shawnee, Kansas, USA
    Thanks for the info gentlemen.

    I appreciate it.

    Tim
     
  9. JerryP

    JerryP Active Member

    Joined:
    Jan 29, 1998
    Messages:
    1,753
    If one is handy at that sort of thing it is an easy fix. The squirrel cage generally slides out as a unit. The motors are disposible. If the motor needs replaced avoid the heating and cooling dealers and go to a business that sells motors. The motors are standard sizes, take the old one with you. I replaced the motor on mine two years ago for $50, Trane wanted over $200 just for motor..
     
  10. Ljutic111

    Ljutic111 TS Member

    Joined:
    Jan 20, 2008
    Messages:
    1,730
    One other thing is to check the rubber motor mounts , since you said it`s getting worse and it`s at least 20+years old , that could be the problem if it`s direct drive and if not then the belt should be changed if that is a belt drive . Like a flat spot on a tire ?? I`m sure you`ll tell us something when you find the problem !!!!!!!!!
     
  11. timb99

    timb99 Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    7,332
    Location:
    Shawnee, Kansas, USA
    Mr. Charles called it correctly.

    It was a motor bearing.

    He walked me through the job, and even for a novice like me, it was a piece of cake.

    Started the fan and was absolutely astonished. I can't remember the furnace running so smoothly.

    Amazing what you get used to when things get worse steadily over time.

    Thanks again to Mr. Charles for his knowledge, kindness, and patience.

    Tim
     
Thread Status:
Not open for further replies.
Search tags for this page
balance hvac blower
,
balance squirrel cage fan
,
blower fan out of balance williams furnace
,

furnace fan out of balance

,
furnace squirrel cage fan not balanced
,
how tight should fan mount be on a blower fan cage
,
how to balance a blower fan
,

how to balance a furnace blower fan