Central Humidifier Overflows

Problem: The humidifier installed in a forced-air furnace is leaking or overflowing.

Background: A furnace-installed humidifier can overflow because it has a defective float valve, a defective float valve seat, because the unit is not mounted level or in the right position in the furnace, or for other reasons. Sometimes a humidifier may create minor overflow when the media pad needs replacement or is rubbing against the side of the unit.

What to do: First check to see that the humidifier unit is level both horizontally and vertically, using a carpenter’s level. If the unit is not level, adjust the mounting. Check the float valve and its adjustment to be sure that it is set for the right water level. (Also check to see that the float itself is not defective; if it is leaking water it must be replaced.) Inside the float valve mechanism there may be a small black rubber button that seals the valve water outlet. If the button shows wear from water erosion, reverse the but ton or replace it. Then make sure the button seats properly and evenly on the float-valve water outlet.

Special advice: In some cases a central humidifier may be installed in correctly so that its opening is located inside the “A” frame of the air-conditioner coil in the plenum of the furnace. In this case, overflowing may be the result of the high static air pressure in this location and the unit should be relocated above the “A” coil.

Helpful hint: When replacing the media pad on the media wheel of the humidifier, make sure that it does not extend past the wheel edges. Do not turn the wheel while it is attached to the motor; damage to the gears may result. Use a solution of 1 part household vinegar and 3 parts water, or a commercial mineral dissolving cleaner to dissolve lime build-up in the humidifier.

Central Humidifier Is Noisy

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.