Noisy Furnace

Well that depends on what the sound is....it could just be a vibration, or it could be the blower wheel accumulating dirt and being off balance...or it could be a bearing....or it could be a loose blower wheel...or rusted out blower wheel....is the blower multi-speed? what is the voltage of the blower motor? Somebody might have put the fan speed in the on position and the fan is running on high speed as opposed to low speed now.....

Vacuum out the motor, also put a couple of drops of light motor oil on each side of the shaft. Furnace motors are air cooled, even with filters, they can become clogged with dirt/dust.

As I said it is 2 speed. The noise I refer to is the blower sounding louder then usual.

Why would changing the filter solve any of the problems You suggest,i.e. bearing, loose blower wheel? I live alone .no one has access to the furnace but Me.

Thanks

oilcan13

If the filter is clogged with dust the fan has to work harder to move the air past the filter. Hence a vibration may indicate a need to allow air to pass through without being slowed. The plenum can cavitate from a pressure change as the air is compressed and released as it passes across the filter. But I would suspect the shaft bearing needs lubrication if it is an older model with an oil port. The newer ones have sealed bearings which need to be replaced when worn.

What does the noise sound like?

I was not to clear on the noise part. Its not a mechanical sound but more like the blower itself getting louder. the whoosh sound that a fan makes. I know everyone is trying to be helpful and I do appreciate all the comments and suggestions. I have one clue that might be the problem if anyone agrees I would appreciate a comment.

I have an ultrasonic humidifier going 24/7 and I have noticed a "white" dust that forms on My mirrors and tv screens I was thinking maybe the "white " dust is forming on My furnace filters and that is why they look clean. I disposed of my last filter and did not check for this "white" dust. I will check the next filter change.

I will keep everyone posted on this perplexing problem.

Thanks

oilcan13

The white dust is probably calcium from the water.

If you're not using distilled or demineralized water that is what happens.

I don't know if that's the problem, but it might be.

Is the dehumidifier a new addition?

Had it since around Christmas. Problem with furnace started around 2 weeks later but I never put 2 and 2 together thinking I may have a problem with blower motor. I use tap water in the humidifier. We get our water from Lake Michigan.

oilcan13

I'm starting to see a pattern here.

"Had it since around Christmas. Problem with furnace started around 2 weeks later."

"I changed the filter and that caused the noisy problem to stop. However two weeks later the same problem started again".

I think lyn is suggesting that the problem is related to the installation of the humidifier.

Can you run the system with a new filter, and the humidifier disconnected. It would seem that the humidifier increases the "effectiveness" of the filter, and air may be drawn from small leaks in the suction side ducting.

All I've got is taking the filter out and putting it back in temporarily quiets the sound.

Air leak? Panel vibration? Loose filter mounting piece?

That's my thought, too.

Is the sound a whooshing sound of air movement or is it an unusual mechanical sound? Do you have an amp probe you can check the amp draw with...? Is it a capacitor run motor? Do you have a capacitor tester? Do you have a new capacitor you can install? Does the motor speed up when you put the filter in? Are you qualified to work on this piece of equipment? How old is the unit....you can tell by the serial number....

OK I think we hit 20...

Based on your observation that a new or no filter seems to cure the noise, I would suspect that the problem is with the filter.

Is it possible that the filters you are using are not the same porosity as the originals?

Lacking further information (which several posters had requested) that would be my guess.

Even if you are using the "same" model filter, companies often change specifications without any indication to the user.

This sounds like a possibility, I would stick with the pleated fiberglass type filters....

You have a point on the filters. Five years ago the most common was at MERV6, and these days the most common is a MERV8 (which has smaller openings to trap more "contamination").

Another possibility is worn and/or under-lubricated bearings in the fluid mover drive.

It sounds like having any kind of air pressure load on the blower makes it strain and creates noise.

First, make sure that the air return vents and duct work are open and free-flowing. Likewise make sure that the hot air vents are not closed or blocked.

Next, (with the furnace shut off!) take a shop vac and a brush with long bristles and brush/vacuum-off the blower wheel. Use some canned air too, to blow off dust/lint/pet hair from the blower and motor. If there is a way to oil the motor and/or blower wheel bearings, as others have suggested, do that too.

If the blower wheel is belt-driven, check the belt for wear.

Then make sure the filter is wedged firmly in place and use some duct tape to seal off any gaps or holes where air might get past the filter.

A plugged filter will decrease the load on the blower and motor, not increase it.

True enough, but it may force the air to take a different, more noisy, path back into the blower.

Like, around a loose bracket or the filter itself.

I was going to suggest the belt but USB beat me to it. I've been amazed at how noisy a heavily cracked (due to aging) belt can be. A lack of flexibility or too much flexibility (as in, like a guitar string) can lead to noise. Look for loose panels as well.

Pretty sure a 5 year old lenox doesn't use a belt driven blower.

In fact I am pretty sure no major furnace manufacture made a residential furnace system that used a belt driven blower in the last near 50 years.

OP might look here for some tips:

Home Inspectors - All about Furnaces

"Furnace blowers come in 2 varieties: some are belt driven and should be serviced every year; modern furnaces use direct drive blowers. They are typically found in the bottom of an upright furnace, directly behind the furnace filter."

Its direct drive.

What type of filter are you using?

Pleated paper.

Does the filter seem to be more restrictive when you change it, than when you put it in? In other words is it being sucked into the return duct with more force?

The simple answer would be to try a fiberglass filter.....

Look pretty much the same as when installed new.

oilcan13

Maybe the clogged filter is restricting the flow so much that the blower is running into a stall condition?

We just did a furnace replacement after 28 years. One thing noted was that the fan motor bearings were worn and the furnace "rumbled" and vibrated a lot due to the fan and fan motor shaft running around the inside of the bearing. These were bronze oilite type bearings. We had an electronic air filter that goes through the dishwasher every few months, so backpressure wasn't an issue.

Could be your motor is mechanically reaching end of life.

Something that happens at about the same time is formation of small cracks in the combustion chamber, if you're using natural gas. This can lead to setting off carbon monoxide detectors in the house if you have them.

The furnace is only five years old. I had the motor replaced about two years ago. Thank God it was under warranty. A motor for this furnace cost around $700.00.

oilcan13

From your earlier description of the noise/sound, I believe you have a high velocity air path making that noise, due to some restriction.

May be time for a stethoscope or short piece of garden hose held up to your good ear to search for the noisy spot on your furnace.

Here are a few things that were not asked:

A. Is this a combination furnace / air conditioning unit ?

B. Is this an Up draft or a Down draft unit ?

C. What is the model number of this Lenox unit ?

D. Is the humidifier mounted before or after the plenum box ?

E. If this is a combination furnace / a / c unit, has there been an inspection of evaporator coil for an obstruction ?

A. yes

B. down draft

C.G60DFV(X)

D. not on furnace, portable unit

E. no

Something i forgot:

A. Has an inspection been done to determine for a restriction on the return duct ?

B. A collapsed flexible duct line ?

C. Are all of the supply registers open ?

A. No. but if there was a restriction it would be noisy all the time , No?

B. All duct is work is metal.

C. Yes

I have to go to work now, so I don't have time to do more research.

The thermostat should be able to be set at blower on only, no heat or cool.

The inspection panel on unit can be removed to observe operation, there should be a delay or kill switch mounted on the housing. When the panel cover is on, the switch is depressed, when you remove the cover, you need to manually depress the switch, then the blower will operate, sometimes this will make it easier to determine if the sound is actually coming from the main blower.

You should check to see if the sound is in the induced fan motor also.

On some units, there is an induced fan motor before or after the heat exchanger. And other units have only one induced fan motor.

Go to JOHNSTONE SUPPLY. Get a copy of book G32-663

Consult pages 62-93

Contains electric schematic, inspection, diagnostic information, etc

Let us know what you find ��

Thanks for all the info but before I go through all that you suggest I am going to wait and see how long the new filter change works. The last one lasted about 2 weeks or so before it started getting loud again. Will let everyone know how it works out.

oilcan13