Topic 'noisy furnace fan' in forum 'Home Improvement' - dslreports.com

Re: noisy furnace fan

Fri, 18 Jan 2013 19:56:39 EDT

lutful posted :

Have the heat exchanger etc inspected when you get the blower shaft replaced.

I had the most bizarre experience with a HVAC guy today. I heard him hit the furnace with a tool when I was not looking and then he claimed that the heat exchanger was leaky and that the furnace must be condemned.

After I insisted there was absolutely no evidence of a leak until now from my CO monitor, he sort of backed away but still applied a wide metal tape on the supposed leak location. He was then trying to sell us a new furnace at a supposedly huge discount. I showed him the door.

*** Sincere thanks to everyone for the suggestions.

a) I put filters on each floor vent and the cold air intakes and the blower sound is muffled quite a bit. I can live with it until I gather up the courage to change the blower speed from HIGH to MED.

b) The clang was actually coming from the damper after the humidifier. I duct taped it open for now although that surface gets quite hot when furnace is on.

c) My son admitted to rolling some marbles down his floor vent in the hope that "they will fall into the flames and melt". They did not come out near the blower and I can't locate them because of bends on the ducts going to his 2nd floor room. However, they are not causing the grinding sound for sure.

Re: noisy furnace fan

Fri, 18 Jan 2013 01:55:56 EDT

aurgathor posted : I'd say it's the bearings. Try to figure out how to lubricate them, although if they're making lots of noise, it may already be too late. If that's the case, you may need to replace the bearings.
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Re: noisy furnace fan

Fri, 18 Jan 2013 00:50:42 EDT

elitefx posted :

said by lutful:

Our gas furnace is 22 years old and the fan is really noisy. The ductwork also makes a huge clang every time the furnace turns off.

What options do I have to reduce the noise a bit?

We went through this a couple years back. Our gas forced air furnace is 45 years old and presently looks and runs like new. It's a Clare Hecla model and built like a tank. I maintain it regularly every year.

Anyhoo, your problem is the blower fan shaft and bearings need replacing. Takes about 20 minutes by a tradesman. As far as the ductwork clang, could just be a vent or damper on the furnace not working as quietly as it used to. Have the heat exchanger etc inspected when you get the blower shaft replaced.

Hint: these old furnaces will last a life time with proper care and maintenance. Spending $5000 on a new one is a complete waste of cash considering the miniscule fuel savings the newer models enjoy over our tried and true well maintained veterans.

Re: noisy furnace fan

Thu, 17 Jan 2013 22:06:45 EDT

Thane_Bitter posted : A few suggestions/ideas, it's possible that:
-The motor bearings are being to fail (new motor)
-The blower has become loose on the motor shaft and rattles (tighten bolt(s)) - applies to belted and direct drive systems.
-If you have AC and if the guy that installed the ductwork added a bypass damper for the AC coil, it could be flapping as the blower kicks in. (the damper should be open in winter, closed in summer)
-someone might have dropped something into the ducts (got kids?) which may have dropped down near the furnace. (duct hunting!)

Re: noisy furnace fan

Thu, 17 Jan 2013 21:54:10 EDT

David posted : might check and see if the motor needs oil or you need a new fan belt. I have one about the same age (yea I know it needs replacing, life keeps happening!) Mine was loud for a while, then I oiled the motor cups on the motor as well as the air drum part. That and replaced the belt with a automotive belt (per my a/c guy working on it) and it's been quiet every since.

Re: noisy furnace fan

Thu, 17 Jan 2013 21:33:00 EDT

F100 posted : My parents had a York furnace for years that was from the early mid-eighties. It did not have a fan for the exhaust, just the blower for the duct work. It also had a pilot light and not the electronic ignition that the newer furnaces use. The blower motor usually has a shaft that turns a "squirrel cage" type fan. I think the whole fan unit uses rubber bushings to dampen the vibration. A bearing in that part may be going bad. Something similar happened to theirs. It was also the blower for the AC so it ran most of the year.

My neighbor has a 6 year old Gas pack and the exhaust fan fins had rusted and designated causing the unit to over heat back at the start of the season. If you change the speed, just make sure the heat exchanger doesn't get too hot on medium. It may be designed for the full air flow of the High setting.

Re: noisy furnace fan

Thu, 17 Jan 2013 18:57:57 EDT

garys_2k posted : Yes, you can disconnect the black wire entirely, put a wire nut on the end that goes to the motor and connect the end that goes to the relay to the blue wire, it'll be fine.

As for "Permanently Lubricated," my furnace says that, too, but they must've forgotten to tell the motor manufacturer -- there are lubrication ports on both ends of the motor. I go in there every couple of years and drop in some oil, figuring the motor manufacturer had some reason to put those caps there.

Re: noisy furnace fan

Thu, 17 Jan 2013 17:30:38 EDT

8744675 posted : I doubt there would be an inducer motor on a furnace that old.

Re: noisy furnace fan

Thu, 17 Jan 2013 17:25:46 EDT

lutful posted : The metal duct just above the furnace makes a clang sound when the blower stops which is really annoying at 5AM.

However, it is the HIGH setting of the blower motor which causes the continuous grinding sound. The MED setting seems to be tolerable because I used the manual fan setting many times.

If I disconnected the black wire coming from IR-1 relay on the controller and tied it to the blue wire from motor, it should run on MED speed during heat call too. But I will wait until less cold weather to take that risk.

P.S. The schematic actually shows just the blower. It is a simple old furnace but worked OK all these years. :)

Re: noisy furnace fan

Thu, 17 Jan 2013 17:15:10 EDT

pike posted : Are you absolutely certain the motor is the source of the noise? Many furnace-related noise complaints can be traced to vibration. Carefully check all hardware on the furnace for proper torque. Set your thermostat mode to "off" and fan to "on" to start the blower motor. Using an open palm and firm pressure, place your hand on various metal surfaces of the furnace and surrounding duct work to see if anything is vibrating (make sure everything has sufficiently cooled off before beginning).

If it does turn out to be the motor, they are generally inexpensive and relatively easy to replace yourself.

Re: noisy furnace fan

Thu, 17 Jan 2013 17:14:06 EDT

Bob posted :

said by lutful:

The label says motor is permanently lubricated.

Unfortunately, the manufacturer probably considers the definition of "permanent" to be 20 years.

Re: noisy furnace fan

Thu, 17 Jan 2013 17:10:56 EDT

jjoshua posted : The inducer motor is up where the exhaust exits the unit.

Re: noisy furnace fan

Thu, 17 Jan 2013 16:54:01 EDT

lutful posted : The house was built in 1989. YORK's model number label may be hidden behind the original installer's support label - I will check.

However, I know there is no draft inducer fan because I stood and watched the call for heat cycle. The faint pilot flame magically becomes a huge hissing flame. There is no fan noise at all just flames. The blower does not actually turn on until a minute later.

I checked the schematic again and it seems the heat call always runs the blower on HIGH. Only the manual fan call runs on the MED setting.

Re: noisy furnace fan

Thu, 17 Jan 2013 16:42:05 EDT

robbin posted :

said by lutful:

There is definitely no "draft inducer" fan. I can see the flames through the grill.

Just because you can see flames doesn't mean there is no inducer. What's the model number?

Re: noisy furnace fan

Thu, 17 Jan 2013 16:38:35 EDT

lutful posted : I have been planning to replace the furnace and a/c and water heater ... for 3 years now. Hopefully next year. :(

Anyway, I took some photos just now. It is a York furnace. The label says motor is permanently lubricated.

There is definitely no "draft inducer" fan. I can see the flames through the grill. Some combustion air seems to come in through the open pipe nearby and the rest from the basement.

There is a schematic attached to the back of the blower compartment door. They seem to be using HIGH and MED speeds (although I only hear high speed operation) and the LOW speed is not being used. Using MED and LOW settings may reduce the noise but I won't risk messing up the wiring in this cold weather.

Re: noisy furnace fan

Thu, 17 Jan 2013 15:53:53 EDT

iLearn posted : Seems like you have a conventional furnace and the fact that it is 22 years old - you should be start budgeting for a new furnace.

I know of someone who had a similar problem. His new furnace was oversized, not saying that this is the problems here at all simply because you have had this for so long and I assume that it just started to make that noise.

Maybe time to get an HVAC guy's opinion on this old puppy :)

Re: noisy furnace fan

Thu, 17 Jan 2013 15:37:11 EDT

ArgMeMatey posted : What he said ... depending on the furnace there is a blower for moving air through your ducts and often a separate draft inducer fan for moving combustion air only. The older GE draft inducers are known for failing noisily. Furnace make, model and installation date may also get you more than a hunch.

Re: noisy furnace fan

Thu, 17 Jan 2013 15:36:56 EDT

lutful posted : It is sort of a lower frequency grinding noise that travels well. We have to turn up TV volume 50% when the blower is on.

I almost wanted to squirt some WD-40 or Jiggaloo but I am worried about any leaks in the heat exchanger and also the smell/toxicity.

Re: noisy furnace fan

Thu, 17 Jan 2013 15:23:42 EDT

John Galt posted : Describe the fan noise...

noisy furnace fan

Thu, 17 Jan 2013 13:17:51 EDT

lutful posted : Our gas furnace is 22 years old and the fan is really noisy. The ductwork also makes a huge clang every time the furnace turns off.

On very cold nights the furnace comes back on around 5AM and wakes us all up. I warm up the house to 23C before bed and turn down the temperature to 16C. I can't turn it down any more for the night because it gets really cold in the bathroom.

What options do I have to reduce the noise a bit?