All ceiling fans produce a slight humming sound when in use. Loud humming is most often caused by resonance or interference.
Resonance is caused by large surface areas, such as ceilings, vibrating and amplifying the sound produced by the ceiling fan. There should be a slight gap between the motor housing and the ceiling. Common causes of resonance are:
- Contact between the housing and the ceiling. (Most common)
- The mounting bracket or the junction box coming in contact with the ceiling. (Note: There should be a slight gap around the perimeter of the junction box.)
- A ceiling with a stucco or rough finish. This is most common with hugger ceiling fans and can be smoothed by sanding the stucco where the canopy meets the ceiling.
Interference can be caused by the connection between a variable-speed control (such as a slide or dial) and the motor of the ceiling fan. Please check that the variable-speed control that you are using is designed for use with ceiling fans.