Problem: When furnace is on, central humidifier makes an unfamiliar noise.
Background: Some noise will naturally be produced by anything that moves air. However, if the central humidifier on your forced-air furnace makes an unusual sound, there may be specific causes that can be corrected. Turn off the electricity at the fuse box or breaker panel or un plug the unit. Then close the saddle valve, which feeds water to the humidifier, and remove any drain tubing so the unit can be taken apart and inspected.
What to do: Remove the lower unit by unfastening latches and pour out any remaining water. If the humidifier was installed using a plenum stiffener, check it to make sure it is securely fastened to the plenum and that all the screws are tight. Then make sure the humidifier is securely attached to the plenum stiffener. Next check to be sure that any set screw in the hub of the media wheel motor shaft is tight. If not, tighten it. Also check to see that the media wheel is still round. If it isn’t, it must be reshaped or replaced. Check the alignment of the wheel, and also make sure there are no bent blades in the blower or the motor fan.
Special advice: If the noise persists, it may be due to the rough edges that were created when the ductwork was cut to mount the humidifier. If these edges are rough, straighten them. Also check the water pressure to the humidifier. If it’s too high, it may cause a vibration noise in the water line (between the humidifier and the saddle valve). This can be remedied by cutting down the flow of water at the saddle valve, or by fastening the water line to a ceiling joist or wall.
Helpful hint: To find out if the noise is coming from the motor, remove the media wheel, reassemble and turn on unit. If the motor is causing the noise, install a replacement or call a technician to do the job.