Hi.
A plain vulgar ceiling fan has a 'magnetic hum' which is not at all mechanical nor from friction. Runs well, very smooth but would like to know what can cause such noise, similar to turning on a large transformer. It is not a typical 60Hz 'electric' hum.

 

Crappy windings. Loose stator or armature plates. Poor quality in general. To be honest, even the pricier ceiling fans sold at the big box stores that I've purchased hum.

If it's not 60 Hz, can you take a guess as to what frequency it is? Perhaps it's a resonance somewhere else in the fan. Have you tried tightening all screws? I had one fan where I had to put a folded paper "shim" under the outer cover to stop it from vibrating.

 

I had to dampen vibrations from the light fixture itself. It was vibrating where it attached to the housing. I used silicone to keep the light fixture from vibrating.

Is the blade assembly balanced? A unbalanced assembly will create a hum. Make a pencil mark on one of the blades. Manually spin the blades several times and note where the marked blade stops. It should stop in several positions. If it stops on the same side most of the time, you need to balance the blade assembly.

 

Hi.
A plain vulgar ceiling fan has a 'magnetic hum' which is not at all mechanical nor from friction. Runs well, very smooth but would like to know what can cause such noise, similar to turning on a large transformer. It is not a typical 60Hz 'electric' hum.

It's most likely source is "lamination rattle" from the non-linear current pulses in the ceiling fan Shaded Pole Motor with a squirrel-cage rotor.

 

Does it change with the speed of the fan??

 

Is this a shaded pole or capacitor run type motor?

 

Buy an expensive "Hunter" brand fan if you want near silence... You pay for quality, which equals less noise. Or, you learn to live with it like the guy who bought the house beside the Interstate and no longer hears the noise because he has become inured to it.

 

Usually that sort of hum comes from vibration of part of the magnetic material, the iron laminations. As the fan rotates the magnetic flux in different areas changes, and that varies the noise.

 

Thanks. There is no mechanical vibration of blades, friction nor covers, it is an audible rumble at the lowest speed, Guessing a capacitor type motor, it is well balanced. It is not loud to bother, but curious of the source of the noise.

 

Sounds like typical Triac controller "buzz" which is accentuated at low RPM's.

 

Thanks. There is no mechanical vibration of blades, friction nor covers, it is an audible rumble at the lowest speed, Guessing a capacitor type motor, it is well balanced. It is not loud to bother, but curious of the source of the noise.

No, I was not describing a blade vibration, but actually within the motor body. That sort of vibration is fairly common in low speed ceiling fans, It often fades out at higher speeds. It was a serious noise issue in one installation I saw because the glass shades on the lights portion resonated at the same frequency and rattled in their attachments. The simple cheap fix was to add rubber bands around the portion of the glass shade that was in the clamping area. That lasted for years, until the lady of the house took the shades off to wash them and removed the rubber bands because she had no idea as to why they were there.

 

Sounds like typical Triac controller "buzz" which is accentuated at low RPM's.

Was going to say something similar.

My neighbor has a ceiling fan on a light dimmer. Anything less than full power it hums like a bird.

Why I say I was going to say something similar is because the first thought I had was that the fan is on a dimmer circuit. Is that the case? If so then you need to find a dimmer that is designed for controlling the speed of a ceiling fan. I'm sure they make them. I just don't know off hand where to find one other than to google it.

 

Well, a dimmer is the wrong choice for any motor right from the get-go.

 

Well, a dimmer is the wrong choice for any motor right from the get-go.

My ceiling fans use a simple dimmer (Triac?) pot on the wall switch, they may be made designed strictly for fans as mine are quiet down to zero rpm.
Motors are cap run AC

 

A power controller designed for motors would be a "motor controller" that can also "dim" a lamp.

But I really have no desire to debate semantics.