High pitched noise from furnace blower

[twinmom]

Our house is 5 years old and we have a trane furnace (80% efficiency) that is the same age. When the blower turns on (whether a/c, heat or just fan), you can hear a faint high pitched whine coming from each of the air vents (not the return vents) in the house. It starts the second the blower turns on and stops as soon as the blower turns off. The closer the vent is to the furnace, the louder the noise, e.g. our kitchen air vent is just above the furnace and it is loudest there. We've had the furnace installer out several times and they say everything is normal. But the noise is constant and annoying. The high pitched noise goes away when the furnace panels/doors are removed - particularly, the solid metal panel that covers access to the fan. The installer cut a new return vent in the metal duct that drops down next to the furnace unit in the basement (thinking we just needed to slow down the air flow in the system), but that did not correct the noise. So he left the panels off the furance and duct taped an air filter over the opening. I don't think the company really has any other solution. Any thoughts on how we can get rid of the noise and get the panels back on our furnace? Is it safe to leave the panels off and/or will it cause damage to the furnace? I'm pretty hooked on this temorary fix given that it alleviates the noise, but we can't leave it like that forever.

 

[Mikepier]

Our house is 5 years old and we have a trane furnace (80% efficiency) that is the same age.  When the blower turns on (whether a/c, heat or just fan), you can hear a faint high pitched whine coming from each of the air vents (not the return vents) in the house.  It starts the second the blower turns on and stops as soon as the blower turns off.  The closer the vent is to the furnace, the louder the noise, e.g. our kitchen air vent is just above the furnace and it is loudest there.  We've had the furnace installer out several times and they say everything is normal.  But the noise is constant and annoying.  The high pitched noise goes away when the furnace panels/doors are removed - particularly, the solid metal panel that covers access to the fan.  The installer cut a new return vent in the metal duct that drops down next to the furnace unit in the basement (thinking we just needed to slow down the air flow in the system), but that did not correct the noise.  So he left the panels off the furance and duct taped an air filter over the opening. I don't think the company really has any other solution.  Any thoughts on how we can get rid of the noise and get the panels back on our furnace?  Is it safe to leave the panels off and/or will it cause damage to the furnace?  I'm pretty hooked on this temorary fix given that it alleviates the noise, but we can't leave it like that forever.

Sounds like there is a vent that is partialy closed, or fully closed. Double check if all the vents are opened. Usually, I get that sound if I close one of the vents in a room that is suplied by the main trunk line.

 

[twinmom]

responding to
http://www.homeownershub.com/maintenance/High-pitched-noise-from-furnace-blower-571368-.htm twinmom wrote:

Sounds like there is a vent that is partialy closed, or fully closed. Double check if all the vents are opened. Usually, I get that sound if I close one of the vents in a room that is suplied by the main trunk line.

All of the vents are open. We've also gone around the house and checked each of the return grills to make sure the sound wasn't coming from a vibrating fin. No luck. This is definitely a noise coming from the unit itself that emanates through the ducting and out of each of our air vents.

 

[Vic Smith]

On Tue, 12 Oct 2010 16:11:03 +0000,
(twinmom) wrote:

Our house is 5 years old and we have a trane furnace (80% efficiency) that is the same age. When the blower turns on (whether a/c, heat or just fan), you can hear a faint high pitched whine coming from each of the air vents (not the return vents) in the house. It starts the second the blower turns on and stops as soon as the blower turns off. The closer the vent is to the furnace, the louder the noise, e.g. our kitchen air vent is just above the furnace and it is loudest there. We've had the furnace installer out several times and they say everything is normal. But the noise is constant and annoying. The high pitched noise goes away when the furnace panels/doors are removed - particularly, the solid metal panel that covers access to the fan. The installer cut a new return vent in the metal duct that drops down next to the furnace unit in the basement ...

"particularly, the solid metal panel that covers access to the fan." What about the other panels? Always had the noise for 5 years? Air passage or bearings are the likely culprit. Depending on frequency, your repairman might not even hear it.

I suppose the load on the blower due to pressure differentials could cause a bearing to squeal. Electronics can squeal, but that doesn't seem to fit your problem. Or maybe some harmonic vibration from a panel, which might be cured by gasketing material.

The load question might be answered by blocking return vents. That could duplicate what leaving the panels on creates in terms of air pressure, though you weren't clear on whether the panels have an effect on that. On my furnaces most access panels have no effect on air flow.

Probably not related, but I thought I had a blower bearing going bad when I had a repairman replace my furnace motherboard. Wasn't real high pitched, more of a rumbling. Didn't even mention it to the repairman until he heard it and made an adjustment with a wrench. Then I noticed it was gone, and he told me what he did. Different furnace than yours though. You might get a different repair man in, or tinker with the panels. For locating sound sources get a mechanics stethoscope. They're cheap, and might get you close to the source. I love this kind of problem, at least when somebody else has it, so keep us posted.

--Vic

 

[DerbyDad03]

Our house is 5 years old and we have a trane furnace (80% efficiency) that is the same age.  When the blower turns on (whether a/c, heat or just fan), you can hear a faint high pitched whine coming from each of the air vents (not the return vents) in the house.  It starts the second the blower turns on and stops as soon as the blower turns off.  The closer the vent is to the furnace, the louder the noise, e.g. our kitchen air vent is just above the furnace and it is loudest there.  We've had the furnace installer out several times and they say everything is normal.  But the noise is constant and annoying.  The high pitched noise goes away when the furnace panels/doors are removed - particularly, the solid metal panel that covers access to the fan.  The installer cut a new return vent in the metal duct that drops down next to the furnace unit in the basement (thinking we just needed to slow down the air flow in the system), but that did not correct the noise.  So he left the panels off the furance and duct taped an air filter over the opening. I don't think the company really has any other solution.  Any thoughts on how we can get rid of the noise and get the panels back on our furnace?  Is it safe to leave the panels off and/or will it cause damage to the furnace?  I'm pretty hooked on this temorary fix given that it alleviates the noise, but we can't leave it like that forever.

Do you have a drop-in filter right next to the blower?

I used to get a high-pitch whistle around the filter slot, which could be heard in other rooms.

I keep a wedge of wood shoved in the filter slot (on the intake side) which pushes the filter away from the return trunk and towards the furnace. Stops the whistle completely.

 

[CJT]

Our house is 5 years old and we have a trane furnace (80% efficiency) that is the same age. When the blower turns on (whether a/c, heat or just fan), you can hear a faint high pitched whine coming from each of the air vents (not the return vents) in the house. It starts the second the blower turns on and stops as soon as the blower turns off. The closer the vent is to the furnace, the louder the noise, e.g. our kitchen air vent is just above the furnace and it is loudest there. We've had the furnace installer out several times and they say everything is normal. But the noise is constant and annoying. The high pitched noise goes away when the furnace panels/doors are removed - particularly, the solid metal panel that covers access to the fan. The installer cut a new return vent in the metal duct that drops down next to the furnace unit in the basement (thinking we just needed to slow down the air flow in the system), but that did not correct the noise. So he left the panels off the furance and duct taped an air filter over the opening. I don't think the company really has any other solution. Any thoughts on how we can get rid of the noise and get the panels back on our furnace? Is it safe to leave the panels off and/or will it cause damage to the furnace? I'm pretty hooked on this temorary fix given that it alleviates the noise, but we can't leave it like that forever.

The fact that replacing the panels with air filters solved the problem indicates to me that it is related to air velocity in the return. The previous attempt to solve it by cutting a hole in the return would still leave a narrow "choke-point" for the air to pass through if it's configured as I visualize from your description.

It seems to me you need to either increase the size of the entire return (which is what the stopgap solution effectively does), and/or perhaps muffle that area by stuffing some loose insulation in there followed by an air filter to make sure it stays in place.

I think the cross-section of the return should be in the same ballpark as the total of the cross-sections of all the ducts away from the furnace (although there's significant leeway).

 

[Stormin Mormon]

The Stucco site is not a help forum, it's an
*advertising* forum that invades real forums
(like "alt.home.repair", part of "usenet")
parasitically in order to generate free
advertising for itself, which continually
advances its search engine placement, thereby
increasing its own revenue through its click-
through advertising commissions.

So the first thing you should do is write them
an email and tell them to quit spamming.

Then try to find your way here through proper
channels. Please do a google search on "Usenet"
and post the regular way.

 

[clare]

The fact that replacing the panels with air filters solved the problem indicates to me that it is related to air velocity in the return. The previous attempt to solve it by cutting a hole in the return would still leave a narrow "choke-point" for the air to pass through if it's configured as I visualize from your description.

It seems to me you need to either increase the size of the entire return (which is what the stopgap solution effectively does), and/or perhaps muffle that area by stuffing some loose insulation in there followed by an air filter to make sure it stays in place.

I think the cross-section of the return should be in the same ballpark as the total of the cross-sections of all the ducts away from the furnace (although there's significant leeway).

When we replaced the furnace in my daughter's condo, and relocated it, the installer recommended the intake plenum (duct) be 15-30% larger than the outlet. I think we ended up about 20% larger. This was a Lennox 84? %.

My Tempstar was installed to the original ducting, which appears to be equal sized, but the total outlet and inlet sizes could still be different. It whisles when I have the filter out for cleaning sometimes - but quiets right down when the filter is installed.

 

[hr(bob) hofmann]

The fact that replacing the panels with air filters solved the problem indicates to me that it is related to air velocity in the return. The previous attempt to solve it by cutting a hole in the return would still leave a narrow "choke-point" for the air to pass through if it's configured as I visualize from your description.

It seems to me you need to either increase the size of the entire return (which is what the stopgap solution effectively does), and/or perhaps muffle that area by stuffing some loose insulation in there followed by an air filter to make sure it stays in place.

I think the cross-section of the return should be in the same ballpark as the total of the cross-sections of all the ducts away from the furnace (although there's significant leeway).- Hide quoted text -

- Show quoted text -

Do you think it is an "air whistle" or could the blower motor need oil???

 

[jw]

On Tue, 12 Oct 2010 16:11:03 +0000,

Our house is 5 years old and we have a trane furnace (80% efficiency) that is the same age. When the blower turns on (whether a/c, heat or just fan), you can hear a faint high pitched whine coming from each of the air vents (not the return vents) in the house. It starts the second the blower turns on and stops as soon as the blower turns off. The closer the vent is to the furnace, the louder the noise, e.g. our kitchen air vent is just above the furnace and it is loudest there. We've had the furnace installer out several times and they say everything is normal. But the noise is constant and annoying. The high pitched noise goes away when the furnace panels/doors are removed - particularly, the solid metal panel that covers access to the fan. The installer cut a new return vent in the metal duct that drops down next to the furnace unit in the basement (thinking we just needed to slow down the air flow in the system), but that did not correct the noise. So he left the panels off the furance and duct taped an air filter over the opening. I don't think the company really has any other solution. Any thoughts on how we can get rid of the noise and get the panels back on our furnace? Is it safe to leave the panels off and/or will it cause damage to the furnace? I'm pretty hooked on this temorary fix given that it alleviates the noise, but we can't leave it like that forever.

Get yourself a very high powered stereo, something like 10,000 watts of power. Insert a DefLeppard CD, and turn the volume all the way up. Leave this play 24/7 and you will never hear the furnace sounds.

 

[jamesgangnc]

Our house is 5 years old and we have a trane furnace (80% efficiency) that is the same age.  When the blower turns on (whether a/c, heat or just fan), you can hear a faint high pitched whine coming from each of the air vents (not the return vents) in the house.  It starts the second the blower turns on and stops as soon as the blower turns off.  The closer the vent is to the furnace, the louder the noise, e.g. our kitchen air vent is just above the furnace and it is loudest there.  We've had the furnace installer out several times and they say everything is normal.  But the noise is constant and annoying.  The high pitched noise goes away when the furnace panels/doors are removed - particularly, the solid metal panel that covers access to the fan.  The installer cut a new return vent in the metal duct that drops down next to the furnace unit in the basement (thinking we just needed to slow down the air flow in the system), but that did not correct the noise.  So he left the panels off the furance and duct taped an air filter over the opening. I don't think the company really has any other solution.  Any thoughts on how we can get rid of the noise and get the panels back on our furnace?  Is it safe to leave the panels off and/or will it cause damage to the furnace?  I'm pretty hooked on this temorary fix given that it alleviates the noise, but we can't leave it like that forever.

Sounds like there is something in that return ducting that is causing it. A stray piece of something sticking into the air flow. Or a small leak. Taking the cover off and puting a filter over that opening means that almost all the return air is going directly into the air handler. A stethscope might help you pin it down closer but I'm thinking you are going to have to open up that return system. How much of the return system is hard duct verses flex pipe? I'd look in the hard duct first. Get some metal tape and start sealing seams from the inside.

 

[Art Todesco]

Our house is 5 years old and we have a trane furnace (80% efficiency) that is the same age. When the blower turns on (whether a/c, heat or just fan), you can hear a faint high pitched whine coming from each of the air vents (not the return vents) in the house. It starts the second the blower turns on and stops as soon as the blower turns off. The closer the vent is to the furnace, the louder the noise, e.g. our kitchen air vent is just above the furnace and it is loudest there. We've had the furnace installer out several times and they say everything is normal. But the noise is constant and annoying. The high pitched noise goes away when the furnace panels/doors are removed - particularly, the solid metal panel that covers access to the fan. The installer cut a new return vent in the metal duct that drops down next to the furnace unit in the basement (thinking we just needed to slow down the air flow in the system), but that did not correct the noise. So he left the panels off the furance and duct taped an air filter over the opening. I don't think the company really has any other solution. Any thoughts on how we can get rid of the noise and get the panels back on our furnace? Is it safe to leave the panels off and/or will it cause damage to the furnace? I'm pretty hooked on this temorary fix given that it alleviates the noise, but we can't leave it like that forever.

Here's my experience. Yours is probably different, so take it for what it's worth. I had a furnace blower go bad there the spot welds, holding the blades in place on the blower wheel, had all loosened up. It started as a quiet sizzling noise, but got louder and louder as the days/weeks went by. I was able to quiet it down by reducing the speed .... it was a plain 4 speed motor, not variable speed, like many newer units. Anyway, I replace the blower wheel. The new wheel ran quiet. And, once I got the old one out, if I would hold one end with my feet, and twist the other with my hands, you could definitely hear small squeaking noises coming from the weld areas. As I said, probably not the same, but maybe?

 

[clare]

Here's my experience. Yours is probably different, so take it for what it's worth. I had a furnace blower go bad there the spot welds, holding the blades in place on the blower wheel, had all loosened up. It started as a quiet sizzling noise, but got louder and louder as the days/weeks went by. I was able to quiet it down by reducing the speed ... it was a plain 4 speed motor, not variable speed, like many newer units. Anyway, I replace the blower wheel. The new wheel ran quiet. And, once I got the old one out, if I would hold one end with my feet, and twist the other with my hands, you could definitely hear small squeaking noises coming from the weld areas. As I said, probably not the same, but maybe?

I had the same issue with the eductor fan on my Tempstar. Dealer who installed it had gone T.U. - local dealer had no parts in stock and I'd have to pay for the parts and labour up front (over $300 IIRC) and the POSSIBLY get up to $200 back.

I took the fan out and brazed the blower weheel web to the hub. It's been quiet ever since (about 6? years now)