In relation to other thread, do furnace blower fans burn out easily?

[geepondy]

I run window fans a lot, even in cooler weather for white noise purposes and I'll typically get 2-3 years out of a $30-40 window fan type before it stops working or gets quite slow.

On the other hand I have central air with a big blower fan in the furnace part inside my condo in the downstairs level. As the upstairs is much hotter then the downstairs, during the summer I tend to let the fan run all the time to circulate cooler downstairs air to the upstairs even if the ac compressor is not kicked on. How do these big fans or in this case fan motors hold up in the long run? Am I considerably shortening it's lifespan by running it near constant for three months out of the year?

 

[LukeA]

Furnace fans are generally better made than household fans. They're designed to fail later rather than sooner.

 

[parnass]

...
On the other hand I have central air with a big blower fan in the furnace part inside my condo in the downstairs level. ... How do these big fans or in this case fan motors hold up in the long run? Am I considerably shortening it's lifespan by running it near constant for three months out of the year?

Do you lube your motor periodically?

When I bought my house back in the last century, I didn't realize that the fractional horsepower electric motor inside my furnace required a few drops of oil periodically. After a few years, the bearings wore out due to the lack of lubrication and scored the shaft, ruining the motor.

I replaced the motor and have followed the manufacturer's recommendations to add 3 drops of oil at each end of the motor every 6 months. The replacement motor has been working well for a couple of decades now and I continue to keep it lubricated.

 

[geepondy]

Ok, I'll take a look at it. What oil do you use to lube it, just regular 3-in-1 oil?

 

[parnass]

... What oil do you use to lube it, just regular 3-in-1 oil?

No, I use 3-In-One Special Blend Motor Oil SAE20 for 1/4 HP motors or larger. It is not their more common "household oil," better suited for smaller motors.

I installed the current motor in Jan. 1988 and have oiled it every 6 months since then, as per the motor manufacturer's recommendations. There is an oil hole at each end of the motor.

 

[turbodog]

Your typical air handler fan will outlast the other components, even if not maintained at all. It your run it 24/7, you might wanna add a drop or two.

However, the added airflow is practically guaranteed to clog up your evaporator coil inside the unit.

I would not do it. Or I would find another way to move air w/o using my duct fan.

 

[parnass]

...
However, the added airflow is practically guaranteed to clog up your evaporator coil inside the unit...

I haven't had that problem. The air is filtered through a replaceable air filter.

 

[eluminator]

The blower in my parent's furnace had grease cups.

 

[Eugene]

I found the same issue, couple years after we moved into our house the fan started squealing one night. I pulled it out and found oil holes and it said to use GE electric motor oil. not having any of that I used a straw to put some mobile 1 5w30 in and the motor ran better than ever.

 

[Galiphrey]

I found the same issue, couple years after we moved into our house the fan started squealing one night. I pulled it out and found oil holes and it said to use GE electric motor oil. not having any of that I used a straw to put some mobile 1 5w30 in and the motor ran better than ever.

By "pulled it out," do you mean you had to remove the motor to find the oil holes? Mine doesn't have any obvious oil holes, but I didn't think to remove it. Previously, I've seen the oil holes plainly visible and well marked with an ARROW and so forth. But not mine...

 

[yuandrew]

The oil ports on blower motors are usually at the very top of the end plate.

On most squirrel cage fans, usually you'll have to pull the entire blower unit out in order to reach the oil port the screwdriver is pointing at since that end is "inside" the fan housing. The oil port on the other end, in my case, could be reached from the front of the furnace if you stick your hand in the little gap between the blower and the furnace side.

I'm more familiar with taking apart Bryant/Carrier furnaces since that's what I have at home and what many of the units in the Mt SAC Air Conditioning class are.

 

[Galiphrey]

Thanks very much, yuandrew. I'll check mine out tomorrow.. I'm sure it could use some oil. It's not making strange noises, but the air flow just isn't what it used to be. I should've been oiling it all this time, but I had figured it was like the new-fangled cars that have no grease fittings anywhere.

 

[cy]

yup.. what you want to do is yank entire squirrel cage assembly out. look for a few retaining screws and it should slide right out.

not only do you need to pay attention to keeping motor lubed. the shaft fan spins upon, also has oil ports. be sure and check fan belt's condition while you are there. it wouldn't hurt to clean all the dust/lint from fan blades. after years in service they can load up enough to greatly reduce air flow. this part requires a garden hose!

than after doing all that... order a custom electrostatic air filter that can be cleaned with a garden hose. one of the best dollars spent anywhere!

unlike new cars built without grease ports, house blower assemblies are made to be maintained. it's not unusual for these squirrel cage blower assemblies to run 50+ years, with proper maintenance of course. the massive unit at my house was installed in 1953, squirrel cage still running strong. but I've done maintenance on all the bearings and replaced fan belt.

some newer house fan motors have a setting to run continuously at a lower speed.

 

[eluminator]

It's not making strange noises, but the air flow just isn't what it used to be.

I guess the reduced air flow is due to dust plugging up dust filters or something blocking air ducts.

There are usually ducts that bring air from the rooms to the fan, and ducts that deliver air from the fan to the rooms. All need to be operational for good air flow.

There is a heat exchanger, sort of like a car radiator, in the furnace or AC that can get covered with dust.

 

[cy]

yup... the most common obstructions to air flow are:

1. air filter clogged
2. lint/dirt loaded on fan blades
3. evaporator is clogged. usually shaped like an A frame. sometimes there's a plate on side you can remove to clean lint. but most are designed to be replaced by an HVAC tech.

if first two items are taken care of and air flow is not back to normal.
you've probably got a clogged evaporator. this is assuming you've taken care of fan belt and lubed all points.

I guess the reduced air flow is due to dust plugging up dust filters or something blocking air ducts.

There are usually ducts that bring air from the rooms to the fan, and ducts that deliver air from the fan to the rooms. All need to be operational for good air flow.

There is a heat exchanger, sort of like a car radiator, in the furnace or AC that can get covered with dust.

 

[eluminator]

Thanks very much, yuandrew. I'll check mine out tomorrow.. I'm sure it could use some oil. It's not making strange noises, but the air flow just isn't what it used to be.

The motors on furnace blowers are usually big "squirrel cage" motors also known as ac induction motors. If they slow up much they will draw excessive current. This would cause the circuit breaker to trip or they will overheat and cause the overtemperature cutoff to trip or the windings will burn out. In the meantime you would probably hear the bearings or whatever was causing them to run slow. Still not a bad idea to check the bearing lubrication.

 

[Eugene]

By "pulled it out," do you mean you had to remove the motor to find the oil holes? Mine doesn't have any obvious oil holes, but I didn't think to remove it. Previously, I've seen the oil holes plainly visible and well marked with an ARROW and so forth. But not mine...

Mine is a squirrel cage and the whole assembly slides out of the furnace (except for the wires which were about 1" too short requiring I disconnect those as well) then I has to take the motor off the cage and fan off the motor to get to the front bearing. It had oil caps down near the shaft bearings.

 

[Marduke]

One problem I have ran into in both my house, and my brothers' is that occasionally (every 5-10 years...) the air mover fan will stop working. However, upon inspection, I found that the control board for the unit had several blade type fuses on it, and one had just burned out. Replaced it with a spare from the car, fired right back up again.