Gas furnace buzzing: with video

[thundermug]

Need some help with a gremlin. I'm handy with most things, but the furnace is mystery to me. Furnace is a Rheem Criterion, about 10 years old.

Upon start up it makes this sound:

It doesn't happen if the furnace is cold. The noise appears on the second cycle as it starts up. It goes away after two or three minutes, usually. It reappears when it winds down.

I tightened the mounting screws for the blower. It seemed to get better, but didn't go away.

I've got a guy coming out on Friday. Last time we couldn't get it to act up and he wrote it off and "no big deal". Hope it's not the bearings. The furnace works fine other than the noise. Any input from experienced professionals would be most appreciated.

 

[mygarageone]

It sure sounds like it is coming from the exhaust fan , I notice it makes the noise before the flame comes on and gets worst as soon as the flame comes on.
Try putting your hand on the end of the motor , if it's vibrating a lot , it's most likely the exhaust fan. Almost sounds like a vane is rubbing on the housing .

 

[koditten]

Another vote for exhaust.

 

[hurstscrambler]

It doesn't take much to remove the inducer fan motor assembly, pull it off and see if there is something loose in there or if the motor shaft is loose. Did you verify what motor is making the noise? It shouldn't be too tricky.

 

[anthony666]

i'm junping on the fan bandwagon too

 

[thundermug]

It sure sounds like it is coming from the exhaust fan , I notice it makes the noise before the flame comes on and gets worst as soon as the flame comes on.
Try putting your hand on the end of the motor , if it's vibrating a lot , it's most likely the exhaust fan. Almost sounds like a vane is rubbing on the housing .

My dad said it sounds like the exhaust fan. When the fan winds down, it sounds just like a metal blade scraping on the housing, as you said.

I'll take a look at the exhaust fan housing. Lots of wires and stuff in front of it. Should I kill the power at the breaker box before I go poking around? If it seems like too much for me, I'll let the tech handle it this Friday.

Hope that's it. Thanks all!

 

[mygarageone]

My dad said it sounds like the exhaust fan. When the fan winds down, it sounds just like a metal blade scraping on the housing, as you said.

I'll take a look at the exhaust fan housing. Lots of wires and stuff in front of it. Should I kill the power at the breaker box before I go poking around? If it seems like too much for me, I'll let the tech handle it this Friday.

Hope that's it. Thanks all!

By all means turn off the power to the furnace , it's not all that difficult to remove that blower assembly. But not sure what they may have used for a sealant , it could be a gasket or some kind of butyl caulk , either way , you will have to reseal if the existing seal is bad.
Just try not to force anything , it will come off the furnace.

 

[thundermug]

So I poked around a little and found the source of the noise. There is a loose screw that can only be accessed from inside the fan housing. I think one of the fan blades is rubbing against it. If I was more familiar with furnace motors / blowers, I would take it apart and fix it. Here is another video showing the problem area:

When the furnace guy is here, I'll video tape or photograph that part of the inspection. I'm sure he'll love that.

Thanks again

 

[RECox286]

When you pull on the forced draft motor with your finger you

are forcing the fan blade against the housing. No big deal to

fix it. Motor comes off with the housing, and is attached from

the inside. When you put it back together, use red permetex

as a sealant (hi temp silicone) that can be had from the local

auto supply store.

Don't fix it, and you are headed for a big $$ fix to replace the

motor assembly when it breaks. If one fastener is loose or

broken, how long before the next one fails ?

Don't forget to give the motor bearings 3 drops of 3-in-one

at least once, preferably twice per year. If you look at the

motor casing, front and back at the top you should see a small

rubber hose sticking out, which is a tube that directs the oil to

the bearings. The bearings will eventually freeze due to lack of

lubrication and require a motor change for bad bearings.

Good hunting

Uncle Bob

 

[lengoldstein]

I had a similar noise problem that I finally diagnosed as coming from the draft inducer fan on my Trane XB80 furnace. The fan wasn't loose or wobbling; it looked as if the whole assembly had somehow sagged slightly out of plumb, just enough to let the fan blades rub against the plenum chamber. I applied a quick-and-dirty fix, which so far has done the trick: I just pulled up the fan motor housing slightly (maybe 1/16") into a fully vertical position, and kept it there by using a nylon cable tie threaded through the edge of the fan guard to suspend the housing from an air-vent grill above it in the furnace casing. Not elegant, but effective. I made sure the part of the motor housing I attached the cable tie to didn't get more than lukewarm when the furnace was operating (no sense trading a buzzing furnace for a house fire), and that the cable tie didn't interfere with the free rotation of the fan. Also, of course, be sure to turn off power to the furnace while you're working on it.
PS -- I'll try to add a picture to illustrate what I did, here:

 

[lametec]

My thought exactly.. Just strap it up somehow. I was thinking some steel wire, but I suppose zip ties work as well.

 

[LS6 Tommy]

That's common with induced draft. The motors really don't like being exposed to the heat and they do move around. The bearings go after a while, too.

Tommy

 

[zmaxmotorsports]

Reminds me of a motor I saw at the supply house today,the guy said the fan was okay though.

 

[Ohmthis]

^^^^ Holy ****!!!

 

[Movover]

Reminds me of a motor I saw at the supply house today,the guy said the fan was okay though.

Reduced shaft model.. very expensive to replace