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Furnace-mounted humidifiers are in thousands of homes across the country. Although many people utilize furnace-mounted humidifiers during the chilly winter season, few understand how they function. So, how does a humidifier work on a furnace?

The heating and cooling experts at Rock Valley HVAC are here to help. 

Rock Valley HVAC consists of some of the best furnace repair technicians in Janesville, WI. Our team understands everything about furnace-mounted humidifiers and can help you with all your heating and cooling needs. Continue reading to learn how a humidifier works on a furnace and how it can benefit your home.

What Is a Furnace-Mounted Humidifier?

Furnace-mounted humidifiers help mediate the moisture level in your home more efficiently than portable humidifiers. They keep your residence warm and comfortable by pumping moistened air into your dwelling, allowing you to overcome the dry winter season.

The humidifier attaches to your furnace’s hot air supply and a water source, providing the moisture the system distributes throughout your home. They work with your heating and cooling system and infuse warm air with the produced moisture. You can adjust the system’s levels through your humidistat and set it to automatically turn on when your home’s moisture level drops below 30 to 50%, making your home feel nice and cozy all winter long.

Types of Humidifiers

Homeowners can choose from several types of furnace humidifiers available, each with its unique strengths and weaknesses. Some focus on efficiency, while others are more cost-effective. Let’s look at some of the most common furnace-mounted humidifiers.

Steam Furnace Humidifiers

Steam humidifiers boil water within the unit to create steam and inject it into the furnace’s airflow. As a result, they are more efficient than other furnace humidifiers and require little to no maintenance after installation. However, steam furnace humidifiers tend to cost more initially. However, it’s a small price to pay for outstanding quality and reliability.

Flow-Through Furnace Humidifiers

The most popular furnace-mounted humidifier, flow-through units, utilize fresh water from your piping system to induce evaporation. It pushes water onto a coated screen so the furnace can evaporate it and distribute moisture throughout your home.

Flow-through furnace humidifiers cost less than most steam units and rank as the most hygienic and reliable models. They require some maintenance but use less electricity than other humidifiers, allowing you to save on your monthly energy bills.

Reservoir Furnace Humidifiers

Reservoir furnace humidifiers utilize a water drum that continually rotates to create moisture. They make an incredibly affordable option but aren’t as efficient as steam and free-flowing units. Reservoir furnace humidifiers also become susceptible to mold growth and require routine maintenance since their water supply remains full.

Despite their efficiency, reservoir humidifiers work great for residents wanting to keep their homes comfortable without putting stress on their finances.

Components of a Furnace Humidifier

Although furnace humidifiers come in several designs, they all require specific elements to function correctly. These elements include:

  • Water: Produces humidity during the evaporation process
  • Water collector: An evaporator pad or something similar that gathers and stores the water
  • Blowing air: Works to pump and distribute moisture through your home
  • Water control valve: Controls flowing water
  • Humidistat: Controls your home’s humidity level

Furnace humidifier components must work together to produce moisture and distribute it throughout your home. Flow-through humidifiers consist of several intricate parts that play a vital role in moisture production.

Below are the essential flow-through humidifier parts.

Water Tap/Supply Line

The humidifier’s water supply line gathers water from your piping system.

Water Inlet Orifice

Diminishes the water flowing to the humidifier’s inlet value.

Water Inlet Valve

This electrically operated valve controls the water flowing to the humidifier. It’s usually controlled by a solenoid that you can regulate using your humidistat.

Water Feeding Tube

Supplies water to the distribution trough and the evaporator pad.

Evaporator Pad

The pad refers to a water collecting medium that stores water until it creates humidity through the evaporation process.

Drain Pan

The drain pan collects excess water from the evaporator pad and empties it into your home’s drain.

Air Duct/Air Damper

A duct mounted on the hot-air side of the humidifier forces air to the unit’s cold-air return. Homes with central air conditioning units must have an air damper.

Humidifier Water Tap

Gathers water from a cold-water line using a saddle valve or something similar with a copper line connecting it to the humidifier. However, some regions don’t allow saddle valves, requiring you to replace them with a gate valve or a traditional ball valve.

Solenoid and the Water Inlet Valve Assembly

The water inlet valve assembly works with the water inlet orifice to control the water flowing to the unit. The solenoid controls the inlet valve assembly, which the humidistat regulates.

Whenever you increase your home’s humidity level, the solenoid pushes water through the unit’s feed tube. Once your residence reaches the correct humidity percentage, the solenoid shuts off and stops the water flow. Your furnace’s transformer powers the solenoid.

Trough and Inlet Feed Tube

The humidifier’s water inlet feed tube connects the top of the unit with the water inlet valve. It provides water to the water distribution trough under the humidifier’s top cover. The trough evenly distributes water across the evaporator panel.

Humidifier Evaporator Panel or Pad

Also known as the water wick, the evaporator pad disseminates water and collects mineral deposits within it, aiding the evaporation process. You must clean or replace the unit’s evaporator pad or panel every season to ensure the unit functions at its optimal efficiency level.

Humidifier Drain

The humidifier drain gathers and disposes unevaporated water from flow-through humidifier units. It removes contaminated and stagnant water from the humidifier, preventing sanitary issues. Humidifier drains are one of the main reasons people prefer flow-through humidifiers over other models.


Allows you to control your home’s humidity level. It works similarly to your thermostat but regulates humidity instead of temperature.

Why Purchase a Furnace Humidifier?

Now that you understand how a humidifier works on a furnace, you can learn its benefits. Consider some of the benefits furnace-mounted humidifiers provide.

Keeps Your House Warm

Furnace humidifiers make your house feel warmer without requiring you to turn up the heat. It allows you to save on your monthly heating costs while keeping you warm and cozy during the coldest winter nights.

Provides Numerous Health Benefits to You and Your Family

Dry weather causes your lips, skin, and even your furniture to split and crack, increasing your risk of infection while diminishing your furnishings’ quality. It can also worsen your allergies and asthma by pushing more dust through the air. Furnace humidifiers keep everything healthy and moist, so your skin, furniture, and home structure stay in immaculate condition all year long.

Can Improve Recovery Time

Colds, sinus infections, and the flu thrive in dry, frigid environments. Although furnace humidifiers don’t prevent you from catching winter-related illnesses, they can speed up your recovery time. The humid air keeps your throat and nasal passages moist, reducing your symptoms while you recover.

Contact Rock Valley HVAC for All Your Furnace Humidifier Needs

Rock Valley HVAC is Janesville, WI’s number one choice for furnace humidifier services. We’ve repaired, maintained, and installed countless furnace-mounted humidifiers, and we can do the same for you at a price you can afford.

Whether you need to know how does a humidifier work on a furnace or want to learn more about the benefits of humidifiers, Rock Valley HVAC is here for you.

 Contact Rock Valley HVAC at (608) 247-4949 and see what our team can do for you today!

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