The Humidifier Solenoid Valve – A Common Frustration

J. Paige Freeland; Marketing Manager, General Filters, Inc.

A common frustration among homeowners who installed and use a whole house humidifier in their HVAC system is a malfunctioning solenoid valve.

A solenoid valve is a control unit that uses electricity to automate the opening and closing of an orifice in the valve body, allowing, preventing, or redirecting the flow of water, gas, or other medium. It is made up of three main parts: the solenoid body, the electromagnetically inductive coil, and internal components (stem, plunger, and spring).

Solenoid valves are used in washing machines, dishwashers, ice makers, refrigerators, vending machines, sprinklers, and many other systems requiring water flow. As such, whole-house humidifiers utilize a solenoid valve to control the amount of water flowing to the humidifier; specifically, an electromagnetic two-way (with 2 ports; inlet and outlet) solenoid valve.

Why do they fail? Can they be cleaned? Or do they need to be replaced?

There are several reasons a solenoid valve may stop working properly.

1. The most common reason solenoid valves fail is that dirt or other contaminants become lodged in the valve seat, preventing the solenoid from opening or closing properly.

Solution: A simple cleaning may be all that is needed.

1. Improper voltages, electrical malfunction, or loss of power can also cause:
   1. Improper opening or closing.
   2. Corrosion.
   3. Burnt-out coils.
   4. Freezing in the open, closed or partially-opened position it was last operating in.

Solution: Check that the manufacturer-recommended voltage to the humidifier and valve are correct.

1. Excessive fluid pressure differentials between the inlet and outlet sides of a valve can cause internal valve components to buzz or clack during operation.

Solution: Check fluid pressure and make adjustments as necessary.

1. A leaky valve usually means that the solenoid is stuck open or partially open. This can be caused by a number of issues, but inevitably creates leakage of liquid. Causes included degraded O-rings, a plunger valve that does not close completely, cracks in the plunger valve seat, or internal dirt particle build up.Solution: The solenoid valve needs to be replaced.

Clean vs. replace

When debris collects in the valve seat of the solenoid valve body, it can simply be cleaned and returned to the humidifier. Corrosion can be removed by soaking in vinegar and water. As with any mechanical apparatus, proper and proactive maintenance and care of a solenoid valve can extend product life and ensure predictable operation. On average, a solenoid valve should last between 1 and 3 years.

Does water supply matter?

It can, yes. Water with high sediment levels can clog a solenoid valve more quickly; however, installing a filter in the water supply line prior to the solenoid valve will reduce the number of particles reaching the valve.

Where there’s water, there’s maintenance; whether you have a decorative fountain, a bathtub with jets, a faucet aerator, or a humidifier.

Your humidifier provides a valuable service in providing healthier indoor air quality. Maintaining it will ensure it will do so for years to come.