Humidifier Not Getting Water? Top 4 Reasons Why

While keeping your home’s furnace well-maintained can be necessary for your comfort, it isn’t always enough to prevent dry, cracking skin, especially during extremely cold weather. That’s why so many HVAC authorities recommend the use of a humidifier to ensure the room air doesn’t become uncomfortably dry, which can result not only in skin irritation but difficulty with breathing.

If you live in an area where the humidity can bottom out seasonally, you probably already enjoy the benefits of a well-functioning humidifier. The one essential ingredient required to keep this product functioning well is, of course, water. If your home’s humidifier is having trouble getting water, the unit won’t be able to do its job. How can this problem be solved? Let’s take a look at how a furnace-mounted humidifier works first.

How a furnace-mounted humidifier works

Although humidifiers can differ from model-to-model, they all operate on similar principles. A furnace-mounted humidifier is attached to either the warm air duct or the return air duct and is powered by the furnace control board. Water is supplied to the unit through a water supply line which is commonly regulated by a saddle valve or another kind of manual shut-off valve. The humidifier operates while the furnace air circulation blower fan is running. As the blower fan runs, the furnace control board sends 120 volts of alternating current to the humidifier or to a transformer which steps the voltage down to 24 volts.

Humidifiers are controlled by a humidistat which monitors the level of moisture in the home’s room air. To add moisture, the humidistat sends voltage to either a water inlet valve, if the humidifier is a “flow-through” style unit, or a drum drive motor, if the humidifier is a “reservoir” style unit.

For “flow-through” humidifiers, the water inlet valve stays open and allows water to continuously flow into the humidifier when the blower fan is running, adding moisture to the room air. The water is distributed through a wick filter to assist in the evaporation process. Any water not evaporated will drain out the bottom of the unit to a floor drain or condensate pump.

On “reservoir” style humidifiers, the water supply line connects to a float and valve assembly which maintains a specific water level in a reservoir pan. When the water level in the pan drops low enough, the float will trigger the valve to open and allow more water to enter the pan. A motor rotates a drum with a filter pad attached through the water in the pan which adds moisture to the air being circulated through the drum.

The home’s thermostat will normally have a setting that runs the furnace’s circulation blower fan only, so if the room air is a comfortable temperature, but still very dry, the furnace can operate the humidifier to add moisture to the air without heat. Good humidifier maintenance requires the wick filter or the drum’s filter pad to be replaced periodically. It’s also a good idea to clean the interior of the unit and/or the reservoir pan regularly. If you live in an area with high humidity during the summer months, the humidifier’s damper, if it has one, should be kept closed until colder weather creeps in and the humidifier is, again, needed.

4 likely reasons why the humidifier is not getting water

While there are other ways a humidifier can malfunction, such as the fan motor not working or the drum not turning, the interruption of the water supply can be a tricky thing to troubleshoot. Here are the top four most likely causes:

  1. Defective water inlet valve – This is a problem that affects “flow-through” style humidifiers where the water supply line connects directly to an inlet valve. You can use a multimeter to test the inlet valve’s solenoid coil or coils for electrical continuity – a continuous electrical path present in the coil – to help determine if the valve is defective. If one or more of the coils test negative for continuity, the valve will need to be replaced. It’s also possible the valve is clogged with mineral deposits that can collect in the component over time. Since attempting to clean inlet valves is usually not effective, this would be another reason to replace the old valve with a new one.
  2. Malfunctioning float & valve assembly – If the humidifier is a “reservoir” style unit, the float can become detached or damaged, making it unable to actuate the water valve to open when the water level in the reservoir pan gets too low. It’s also possible for the valve itself to wear out. Depending on the humidifier model, you may be able to replace just the float, although usually the float and valve are sold as an assembly.
  3. Clogged saddle valve – The shut-off valve which controls the water flow through the supply line to the humidifier could be clogged with sediment or calcium deposits. Saddle valves, which are commonly used to regulate small water supply lines, are relatively inexpensive and usually easy to install. This is a good place to mention that self-piercing valves are not recommended for humidifier water supply lines as the hole created by such valves is so small that it can easily become clogged by sediment deposits, making impeded water flow a reoccurring problem.
  4. Faulty humidistat – If the humidistat is incorrectly set or isn’t working properly, the humidifier may not fill with water. Try turning the humidistat to the highest setting and listen for a “click”. If you do not hear that “click”, then the contacts in the humidistat are not closing and the part will need to be replaced.

Finding the right humidifier parts at Repair Clinic

As your repair partner, Repair Clinic.com takes the stress out of finding the exact humidifier replacement part you need. To view a complete list of compatible parts, type the full model number of the humidifier into the Repair Clinic website search bar. You can then use the “Part Category” and “Part Title” filters to refine that list to locate the specific water inlet valve, float & valve assembly, humidistat, wick filter, or drum filter pad you’re looking for. In addition to stocking original manufacturer replacement parts from such top name brands as Bemis, Bryant, Carrier, Goodman, Holmes, Honeywell, Skuttle, and York, Repair Clinic also supports both do-it-yourselfers and technicians with free heating and cooling product “how-to” videos, articles, diagrams, and more. Getting that humidifier back in good working order is a lot easier with help from Repair Clinic!

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