Squirrel cage gone bad?

[PCustoms]

Heard a low rumbling tonight while making dinner, figured the fridge got pushed too far back again, nope. Got louder, figured helicopter (life flight runs up the valley), went outside and dead quiet. Finally figured out it was the blower on the furnace.

Blower has been set to circulate all summer, no issues. Been running the heat in the mornings about a week, no issues. Used it last night to deal with some high humidity (cooking disaster) and oddly smelled something musty, but not near the furnace. Blower was fine all morning, seems to have started sometime today or tonight.

Blew everything out tonight, not really dirty at all. Checked for missing weights and didn't see any signs one fell off, no bent vanes either. Lubed the motor best I could without tearing it out, didn't seem to matter.

Did the front bushing just go caput, or is there something else I should look at before firing the parts cannon?

 

[mm08822]

Mine went a few years ago , 28 years old. I oiled the bushing and got a few more days out of it.

Meanwhile, pulled the blower to read the nameplate. While I found a few sources on the web, grainger was in driving distance for immediate purchase inhand.

Replace the cap at the same time.

 

[PCustoms]

Mine went a few years ago , 28 years old. I oiled the bushing and got a few more days out of it.

What symptoms? I'd expect grinding/squeaking, but all I have is this sudden vibration

Meanwhile, pulled the blower to read the nameplate. While I found a few sources on the web, grainger was in driving distance for immediate purchase inhand.

Replace the cap at the same time.

I assume you changed just the motor, and not the whole blower?

 

[mm08822]

Not recalling all of the details but it was a low whine that changed pitch after a minute or so of running.
Initially, source of noise hard to find as it carried through the ductwork.
Once I determined the noise cycling with the furnace, I pulled the entire squirrel cage housing. Squirrel cage didn't show signs of excessive looseness on motor shaft. Had to pull motor to read nameplate. That's when I saw bearing was trashed.
Oiled it, put back together, ran it while I searched for same motor. Shortly after, motor not able rotate w/o help at startup.

Had to drive 1 hour to grainger b/c it was in stk and the complain dept was complaining.

Simple replacement. Just mark the orientation of motor and wheel for quick re-assembley.

Only motor changed out.

 

[PCustoms]

Not recalling all of the details but it was a low whine that changed pitch after a minute or so of running.

Yeah, that's the weird thing here, no whine/squeak, just the vibration

Initially, source of noise hard to find as it carried through the ductwork.

Exactly. Stupid thing shakes a little at the blower, which resonates in the rest of the cabinet and is shaking the duct.

I can probably get the motor details with it installed, but I think I'll pull it tonight to get a better look as it really doesn't feel like a bearing issue.

 

[mm08822]

Clean the wheel evenly while out. Important so you dont introduce vibration from a partial clean. Have a toothbrush and small bottlebrush ready. Compressed air alone may be insufficient.

 

[PCustoms]

Got this on the way out this morning

 

[bonneyman]

Blower wheels can be finicky things. At 1075 RPM, even the tiniest balance issue can be enough to start vibration noises. I've had blower wheels that developed tiny cracks at the junction point of the individual blades to the cage rim. Even at the hub junction to the cage. At speed - or at different points of the run up - minute flexing of the metal will cause vibration.

My furnace squeaks while starting up on heating speed, but sounds fine on cooling speed. Cage is clean. I'm thinking it's the cheapie sheet metal motor supports on the newer unit, flexing on start as it absorbs the torque. But at run speed it's fine. Just hasn't gotten bad enough to tear the whole assembly out and replace them.

 

[fitter30]

Failures on wheels is the hub gets loose from the wheel ( crimp loses it grip). The outer part of the wheel that holds the blades fails wheel will turns oval and loses it strength to hold blades, the set screw loosens starts to groove the shaft or worse. Loose hub to shaft can also start wheel rubbing on housing . Set screw might need to be replaced.

 

[aggie113]

Mine just made a horrible racked a few years back. Thankfully very simple to source (Amazon?) and replace. Thankfully it wasn't too cold the first time I tried to use it that season.

 

[PCustoms]

Mine just made a horrible racked a few years back. Thankfully very simple to source (Amazon?) and replace. Thankfully it wasn't too cold the first time I tried to use it that season.

Different fan, and easier to change (doesn't involve kneeling and wedging myself between the unit and the wall)

 

[mm08822]

Mine just made a horrible racked a few years back. Thankfully very simple to source (Amazon?) and replace. Thankfully it wasn't too cold the first time I tried to use it that season.

That's the inducer fan, OP's is the big blower below.

 

[PCustoms]

LMFAO, could it be this simple?

 

[Innovate1]

LMFAO, could it be this simple?

That could easily be the issue! Easy to find out...

 

[PCustoms]

That could easily be the issue! Easy to find out...

Yep, that's all it was!

Funny when I was in it last night I was staring at a perfectly clean square inside the cabinet, wondering what was there...

 

[Fav Onefour]

You found it before I could respond. I was going to suggest checking to see if it had buildup on the fan. Apparently it had a big spot of buildup.
Fine dust or material can also build up over time. I don't know why it would accumulate unevenly, but I've had it happen.

We have large squirrel cage fans around the farm. They are mostly used to force air in dryers and bin aeration fans. No pre filters, just grating to block debris. It doesn't take a lot to give them the wobbles. We had one fall with super cold temps during drying and the damp air/steam off dryers started to cause accumulation on the fans. The ice did not build up evenly. It was a hassle too. There isn't a sensor for vibration on that equipment so we had to keep checking the fans. The dryer fans are 50 hp units and wobble is going to wreck a lot of parts around that end of the unit. It was a real riot walking around with flashlights at all hours to look for wobblers.

 

[bonneyman]

Looks like it was the info label on the inside of the filter door, and after so many years the glue dried out and released it into the air stream.

 

[Innovate1]

At least it was an easy fix.

Reminded me of a fix I did on a wheel that was out of balance. The furnace fan in the attic vibrated just enough to make some rattles below it. Found some details on a method for balancing using only amplitude measurements with trial weights in different positions. Had access to some scrap wheels for additional clip on weights. Used the element of a cheap piezo buzzer for the vibration sensor. Was able to reduce the vibration quite a bit.

 

[PCustoms]

At least it was an easy fix.

Yep.

The night it started it was late and I wasn't dressed for tearing into things, so I just blew it out and shut it off after no change.

Made it a priority after work last night thinking I'd have to scrub everything down. Spent more time grabbing a few tools then actually working on it, as soon as I slide the assy out it was obvious.

 

[AC-WC]

You screwed up-correct answer is Honey, I have to X new tool to fix this

 

[PCustoms]

You screwed up-correct answer is Honey, I have to X new tool to fix this

Unless you're willing to be my sugar daddy, that's not an option here

 

[PoorUB]

I installed a humidifier on a air handler with the owners manual in the blower wheel. The customer said the unit shook like that since new, a few years earlier. They even had the installer come out and look at it and say it was normal! (Scum bags! Did they even look?) I took out the manual and started it up and the customer was shocked at how smooth it ran.