[sharkman]

I have an attic fan (installed about 2 years ago), after it turns on it makes allot of noise. I was wondering if replacing the fan motor is a big job and is it done from the inside. Any help would be greatly appreciated.

[JohnWill]

I really doubt the motor is the noise generating component. It's far more likely to be the fan blades or simply the airflow pattern. If you run the motor by itself either removing the fan blade (direct drive) or the belt (belt drive), I think you'll find it's very quiet. This is not an uncommon complaint.

It would help if you told us more about the exact size and installation of this fan.

[muppy03]

Is this a ceiling fan? check the fan shaft is sitting correctly in the ceiling mount. A lot of ceiling fans have a notch and groove attachment. The fan will work if it is not sitting properly but will make a very loud humming noise.

[JohnWill]

I was assuming the fan was running, just noisy. I've seen this for several attic fans, one had unbalanced fan blades, and the other needed better mounting. All of the fans I've used have had a flat on the motor shaft for alignment of the pulley or blade.

[Koot]

I'm assuming the fan is an "attic" fan mounted either on the roof that has a dome top, or in a gable vent with shutters. I have had to replace a couple of roof mounted attic fan motors over the years, as well as replacing the entire unit. When replacing the motors I was always able to get an exact motor replacement, which made replacing the motor in the mounting brackets a perfect fit. However, I was told that there is a universal replacement motor available with various mounting pieces that supposedly works with practically any brand.

I have never had a noise problem due to the fan blades being out of balance. I wouldn't think out of balance blades would be a problem since there is nothing that can come into contact with them to bend them.

I had two roof mounted power ventilators that needed replacing due to the PVC (plastic) domes had deteriorated and cracked. I replaced them with a very nice aluminum domed unit made by Nutone Broan. The model number is #358. http://www.broan.com/display/router.asp?ProductID=2468

Nutone Broan has always had replacement parts (e.g. motors) available for their products for decades whereas some other manufacturers have not...or they go out of business.

It's not much fun trying to get something to work that isn't a direct replacement when there's not enough light, it's hot, and your work place is not desireable. Be careful, especially if the attic fan is not directly over a plywood floor - you don't want to make a mistake and step through the ceiling below. It's starting to get hot up there this time of year...I wouldn't wait too long before taking care of it...

[Zeppfan]

Any collection of dust and dirt on any fan blades can cause an unbalanced situation.

Balancing needs to be done on any object being spun at a higher rate of speed(RPM).

Car motors are balanced, tires are balanced, electric motors and fans are balanced. Even your lawn motor blade is balanced.

If an object is spun at a high rate of speed without the object being balanced, vibration, noise, shaking, and extreme damage can occur.

The internals of the electric motor and fan blade within the ceiling or attic fan are all balanced as well. Even the shaft bearings are designed to be a balanced entity of the motor. If the bearings fail, damage occurs by either by locking up the motor, causing excessive vibration, and/or causing internal damage.

In this situation, it sounds as if the bearings have met their usefullness, or the fan blade has been damaged or bent(causing an unbalance).

[wacor]

well since sharkman has not replied I guess we might as well clear up some things. as mentioned by John Will it would help to know more info on the fan specifics. I was assuming this was a fan mounted in the ceiling that vented into the attic rather than a fan as Koot referred to.

a description of the noise might help too. is it a growling or a ticking noise. if one is familiar with motors they can usually tell by sound if the motor bearings are the problem. one way to also check that would be to manually spin the fan and see if there is any noise evident. and check the motor shaft for looseness which would indicate a bearing problem.

if it is more of metalic ticking sound then it could be the fan blade hitting the sides of the fan assembly

[JohnWill]

The notion that the fan blades can't become unbalanced is bunk. The problems I've had with typical attic fan motors is usually they simply freeze up after a few years operation. I've found replacements that will bolt in for all of my fan issues. I've had four houses and a host of attic fans over the years, this house has four of them, so I'm getting pretty good at replacing motors and balancing the fan blades.

Slight settling can warp the fan enclosure and cause a blade to hit, that alone is frequently enough to bend them. Even a small bend is enough to unbalance them and make them vibrate. I've also had mud wasps build a nest on the blades, I can assure you that unbalances them!

[sharkman]

sorry for thre delay.

The fan is an attic fan, roof mounted. I does in fact work, its just very noisy. The make is NuTone and its rated at 1500 cfm. Hope this helps.

[sharkman]

The noise is more of a vibrating sound, definetly not metal on metal.

[wacor]

take the fan blade off. see if the motor shaft wiggles. it should be solid and not be able to move side to side or the bearings are bad. if the noise stops with the blade off then it is a fan blade out of balance i would guess. another thing to do is to press on the fan case and see if the noise changes. could be it is mounted in a way that is telegraphing the normal vibrations.

[JohnWill]

I'd bet on the fan blades, taking them off will help you figure it out.

[sharkman]

I gave the motor a wack and the noise went away.
Question, how do I take the blades off?

[wacor]

Originally Posted by sharkman

I gave the motor a wack and the noise went away.
Question, how do I take the blades off?

Take a picture. There are a couple of ways a fan might be mounted.

hitting it though raises any number of ideas.

[hewee]

Originally Posted by Koot

I'm assuming the fan is an "attic" fan mounted either on the roof that has a dome top, or in a gable vent with shutters. I have had to replace a couple of roof mounted attic fan motors over the years, as well as replacing the entire unit. When replacing the motors I was always able to get an exact motor replacement, which made replacing the motor in the mounting brackets a perfect fit. However, I was told that there is a universal replacement motor available with various mounting pieces that supposedly works with practically any brand.

I have never had a noise problem due to the fan blades being out of balance. I wouldn't think out of balance blades would be a problem since there is nothing that can come into contact with them to bend them.

I had two roof mounted power ventilators that needed replacing due to the PVC (plastic) domes had deteriorated and cracked. I replaced them with a very nice aluminum domed unit made by Nutone Broan. The model number is #358. http://www.broan.com/display/router.asp?ProductID=2468

Nutone Broan has always had replacement parts (e.g. motors) available for their products for decades whereas some other manufacturers have not...or they go out of business.

It's not much fun trying to get something to work that isn't a direct replacement when there's not enough light, it's hot, and your work place is not desireable. Be careful, especially if the attic fan is not directly over a plywood floor - you don't want to make a mistake and step through the ceiling below. It's starting to get hot up there this time of year...I wouldn't wait too long before taking care of it...

Funny thing about these fans is they don't cost that much and cost less if they are on sale.
But if only the motor goes out you have to but a whole fan again because you can not just buy the motor unless you pay more then getting the whole unit again. Maybe getting the same brand gain you can change out the motor but if you get them on sale like my dad did then another brand you can not change out parts so you have to go up on the roof and take the whole fan out and put the new one in.
So worth getting a brand that you know you can get a new motor for or can get the whole unit again and then just change the motor.