Everything you need about an air handler

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Last updated: 
March 18, 2024

Understanding Air Handlers: Components, Types, and Comparison with Furnaces

What is an Air Handler?

An air handler, also known as an air handling unit, is a device designed to circulate and control air through air conditioning, heating, or ventilation systems. According to our research, the metal box of an air handler unit usually comprises cooling and heating elements, a blower, dampers, and filter racks. Most of the time, air handlers are linked to the ductwork ventilation system, which is responsible for distributing the air throughout the entire house before taking it back to the air handling unit.

Air handlers are usually installed in well-ventilated areas where the device is kept away from humidity and condensation. It is not recommended to place your air handler in the attic, as a leak could potentially flood your entire house and cause damage to your roof.

Types of Air Handling Units

Homeowners and building owners have different needs regarding the rooms to be cooled down in the summer or heated up in the winter. As a result, there are several types of air handling units available on the market:

  • Insulated air handlers: Designed for silent heating or cooling operations.
  • Hydronic air handlers: Specifically created to work with boilers.
  • Single speed air handlers: The fan motor works at a single fixed speed.
  • Five speed air handlers: Preferred to single speed air handlers due to increased operation precision and more effective air circulation.
  • Variable speed air handlers: Boast several essential functionalities, including adjustments for humidity levels, consistent temperatures, and air quality.

Differences and Similarities Between a Furnace and an Air Handler

Furnaces generate heat for a house or building by burning fuel and distribute the resulting heat throughout the rooms via ducts. In comparison, an air handler blows either cool or hot air in the building via ducts. The two devices look similar, which often leads to confusion, but their uses, specifications, and applications differ.

The primary difference between a furnace and an air handler lies in the heating system they use. Furnaces typically work on heating oil, liquid propane, or gas, while air handlers are commonly paired with an electric heat pump. Furnaces comprise four essential parts: the combustion chamber (burner), vent, heat exchanger, and blower. Air handlers, on the other hand, use refrigerants to transfer heat energy and push air throughout the house using a blower.

Despite their differences, furnaces and air handlers share some similarities. Both devices employ filters to maintain air quality by trapping impurities and dust from the air. They also constantly incorporate outside air into the flow of air passing through the building and are controlled by a thermostat.

In-Depth Look at Air Handler Components


Filters are essential for keeping germs, allergens, and dust at bay. They come in a wide range of designs, such as pleated or electrostatic, and are the first barrier used in air handler units to keep vital components clean and dust-free. Regular filter maintenance and replacement are crucial to prevent damage to other components and ensure optimal performance.


Cooling down or heating up a room can reduce moisture in the air, leading to various issues such as dry eyes, sore throats, dry skin, and allergies. Humidifiers help maintain a comfortable air quality by adding moisture to the air stream. There are several types of humidifiers that can be implemented in an air handler unit, including spray mist humidifiers, vaporizers, evaporative humidifiers, and ultrasonic humidifiers.

Fan or Blower

The fan or blower, typically a squirrel cage blower, is responsible for moving air with the help of the air conditioning unit. It can work at a single speed or provide various speed settings, with flow rates controlled through dampers or vanes. Large commercial buildings may use multiple blowers situated at the end of the air handler units, and additional fans can be installed within the return air duct for increased power.


Unbalanced fans can cause wobbling and vibrating, leading to noise, reduced efficiency, restricted airflow, and potential damage to the system. Special balancers are used to keep the fan in place and ensure a smooth spin, maintaining the integrity of the air handler unit.

Heat Recovery Device

Heat recovery devices, such as recuperators and rotary heat exchangers (thermal wheels), are used to cut back on energy costs and increase capacity. Recuperators comprise metal or plastic plates linked with air paths, transferring heat via airstreams. Rotary heat exchangers use a rotating matrix that works in both airstreams, absorbing and releasing heat during rotation.


Control buttons provide adjustments for every feature of the air handling unit, including supply and mixed air temperature, humidity levels, air quality, and air flow rate.

Vibration or Sound Isolators

Air handler blowers can be noisy, and the vibration and noise could be transmitted throughout the building via the ductwork. To minimize this issue, manufacturers implement vibration and noise isolators made of a rubberized material that separates the fan compartment from the rest of the components, preventing sound and vibration from passing further into the ducts.

In conclusion, air handlers are essential components of air conditioning, heating, and ventilation systems. Understanding the different types of air handlers, their components, and how they differ from furnaces can help homeowners and building owners make informed decisions when selecting the most suitable system for their needs.

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