Loud humming noise from furnace blower motor

[545GAlady]

We had a Lennox SL280v two-stage furnace installed for our first floor a few weeks ago, and we are very satisfied with the performance. However, when the unit runs you can hear a loud hum coming from the blower. The hum seems to change as the blower ramps up and down. I suppose its coming from the ecm motor. Our upstairs SL280v which was installed last summer has a very similar noise, except it is less noticeable. Any ideas?? Thanks.

[STEVEusaPA]

What did the installer say, when you called him back to look at it? Noises can be difficult to diagnose without standing there listening. Could be anything from simple vibration from something touching the cabinet to loose motor mounts--and anything in between. If you just had it installed, get the guy back out

[545GAlady]

I called him back yesterday, and he is coming out early next week since he's been very busy. The noise is only noticeable if you are standing in front of the furnace. It almost sounds like a quiet jet engine.

[545GAlady]

I was reading another thread about someone's 2 day old Lennox SLP98v making a slight buzzing/whine from the blower and the noise sounds very similar to the noise from our furnace.

[545GAlady]

I haven't updated this thread in several months, but I came back to it since the furnace is still producing the loud noise. We have had a tech look at the system and he said everything sounds normal. He even lowered airflow a lot, and that still didn't help. He said return air is proper and verified that duct size is correct. I also remember him telling me that ECM motors are suppose to make this noise and he checked for anything vibrating and found nothing wrong. I'm getting to the point that I'm sick and tired of the noise and no one is willing to help. However, we now use a totally different HVAC company now because we started to become unsatisfied with the one who installed the furnace, and we have been using them for years until now. I have yet to call someone out from the different company to check out the noise. I thought variable-speed furnaces are suppose to be quiet. Do any of you have any further opinions???

[t527ed]

vs blowers are normally very quiet, if installer can not find a problem then insist they get a Lennox field rep out to look at it.

if they refuse then contact Lennox directly, they will get the dealer moving.

[545GAlady]

vs blowers are normally very quiet, if installer can not find a problem then insist they get a Lennox field rep out to look at it.

if they refuse then contact Lennox directly, they will get the dealer moving.

Thanks for your input. Are the actual motors suppose to emit any type of humming sound? I will call the installer back sometime this week. Hopefully he can fix the other problems with the furnace, such as the gas valve (everytime the furnace runs in heat mode, a smell of natural gas fills the utility room up. Not a concern at this very moment since heating is not being used now and there's currently no smell) and the control board acting up (dual-fuel wasn't set up properly and the blower won't slowly ramp up when its suppose to). Any other thoughts?

[kdean1]

A gas smell!? I'd insist he come back right away, even though it is not heating season. There should NEVER be a gas smell. It makes me wonder what else he might have done wrong.

[cowboyjcmo2004]

This is the Ask Our Pro's forum, and only Pro members that have been vetted by the AOPC may post advise, commentary, or ask questions of the OP here.

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[beenthere]

cowboyjcmo2004, this is the Ask Our Pro's forum, and only Pro members that have been vetted by the AOPC may post advise, commentary or ask questions of the OP here.

You can find the rules for posting and qualifications here.

Your post has been deleted.
Further infractions may result in loss of posting privileges.

[545GAlady]

A gas smell!? I'd insist he come back right away, even though it is not heating season. There should NEVER be a gas smell. It makes me wonder what else he might have done wrong.

You can only smell gas when the furnace is ON. For example, there's no smell now and there hasn't been one since the furnace last ran in April. I suppose its the furnace gas valve where the smell is coming from?? Unit does a good job on heating. We do not need heat yet until probably October. Last time the tech was here, he checked all connections on the gas line and they were fine. What's funny is that the same techs who installed the furnace installed the upstairs furnace a year back, and it is the same model (but a smaller size). It has no smell at all when it runs. Could the new furnace be defective (or at least any of the components)??? Do y'all want any pics of the installation?

[CraziFuzzy]

As said, you should never have a gas smell, whether the unit is running or not. That is the sole purpose natural gas is odorized, so you know where there is a serious problem. If you are smelling it, at ANY time, there IS a serious problem.

[545GAlady]

As said, you should never have a gas smell, whether the unit is running or not. That is the sole purpose natural gas is odorized, so you know where there is a serious problem. If you are smelling it, at ANY time, there IS a serious problem.

Thanks for the reply. Most of the time the smell was small, meaning you can only smell it standing a foot or less away from the furnace. There's only been one time when the smell spread to rest of the small utility room. The smell went away a few minutes after the furnace shut off. We will probably go ahead and schedule our fall tune-up and have the technician look into the cause. Hopefully the issue will be fixed.

[JDenyer232]

Again any smell of gas is a warning. Call them out and have it fixed ASAP!

[545GAlady]

Again any smell of gas is a warning. Call them out and have it fixed ASAP!

I appreciate the advice, thanks. I will call the installers back ASAP tomorrow. I'm surprised that the installers never noticed any gas smell when they first tested the furnace in heat mode right after installation, but the issue is more important than that right now and soon it will be solved.

[545GAlady]

Here's an update... Unfortunately the company can't come back out until two weeks from today. They will be here for our fall inspection. We couldn't get them to come out any sooner. I'll be mad if they can't find the gas problem. The other issues include the blower not ramping up like it should, and of course the blower motor producing a high whining noise. I'm starting to wonder if having a Lennox furnace is not okay with being matched up with a Trane heat pump in dual fuel applications. At least the indoor coil matches the heat pump. Does the indoor unit have to be the same brand as the outdoor unit in dual fuel systems?

[hvac hero]

They aren't a very reputable company if they are putting you off for 2 weeks. If a paying customer called for a no ac call, they'd be out that day or the next. I'd spend a little money and find the very best company you can to look at it. Sometimes it's better to do that than to put up with the aggravation of the first company.



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[hvac hero]

Oh 1 more thing I thought of. You mentioned in the original post that the motor hums and it changes pitch as the motor ramps up. This is a long shot but I'll just mention it any way. Some installers seal the return plenum with metal tape. If they don't push the tape down firm to the surface, sometimes it will vibrate and make quite a bit of noise. It would also change with the speed of the motor. Probably not it, but figured I'd mention it anyway.


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[545GAlady]

They aren't a very reputable company if they are putting you off for 2 weeks. If a paying customer called for a no ac call, they'd be out that day or the next. I'd spend a little money and find the very best company you can to look at it. Sometimes it's better to do that than to put up with the aggravation of the first company.



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I've been trying to talk my husband into calling someone else, but he wants to go ahead and wait two weeks since there's no gas smell now. He's not that concerned about the issue as much as I am.

[545GAlady]

Oh 1 more thing I thought of. You mentioned in the original post that the motor hums and it changes pitch as the motor ramps up. This is a long shot but I'll just mention it any way. Some installers seal the return plenum with metal tape. If they don't push the tape down firm to the surface, sometimes it will vibrate and make quite a bit of noise. It would also change with the speed of the motor. Probably not it, but figured I'd mention it anyway.


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Thanks for the input. The installers sealed everything up with mastic. Whenever I pull the filter out, the pitch greatly lowers, but once I put it back in, the pitch rises again.