How Does An A/C Handler Work?

The air handler holds the components that are responsible for moving the air throughout your home. Most ACs in residential and commercial spaces are split types, which means that they have two units – indoors and outdoors. The air handler is the indoor component of every AC.

How does an A/C handler work? Air handlers are intended to distribute the heat or cool indoors evenly. The air handles are composed of an air filter, coil, and blower motor – these three work simultaneously to distribute air.

A Must Read: What Is The Difference Between AC Compressor And Condenser?

You will know how the AC handler and its components work as you read this article. I will also discuss the needed repair and maintenance to have a smooth-flowing air handler.

Air Handler

The air handler is a device or unit that circulates air throughout your home for your comfort. It is installed indoors and operates with both heating and cooling components of your AC system.

The main role of the air handler is to recondition the air from outdoors. The re-conditioned air will then serve as the air supply indoors.

It will also remove all the exhaust air to provide comfortable indoor air quality.

If the climate is cold outside, the AC handler will re-condition the air to heat by a recovery unit. Yet, the AC handler could also re-condition air through a heating coil.

If the climate is hot or warm outside, the AC handler will re-conditioner the air to be cool indoors.

A handler uses a cooling coil to supply cool or cold air temperature inside your home.

The air moves to the air handler and passes through an air filter to purify the air and eliminate contaminants.

The filtered air will then go through the cooling coil or evaporator coil and make the filtered air cool.

After the air has been filtered and cooled, it will be pushed out into your indoor space.

The air handler is a large metal box holding three components of your AC – air filter, coil, and blower motor.

It is connected from a duct-work that dispense air throughout the indoor space and returns it to the air handling unit.

Air Handler Components

To further understand how an air handler works, you must also know and understand its major components.

Air Handler Filter

The air filter is the device or component between the intake vent and the fan. It is responsible for purifying and cooling the outside air before it enters the home.

It is usually found in the return air duct or the blower compartment.

Without air filters, the air circulated by the air handler could pose a serious threat to your health.

That being said, the air filter is a vital component of air handlers because this traps the pollutants and contaminants.

Yet, air filtration usually happens when the expanded air is brought back into the AC equipment.

Below are three kinds of air handler filters used.

  • HEPA Filters – very efficient in removing minute particles and airborne bacteria.

  • Electrostatic Filter – uses highly charged electrodes to remove air particles and ionize the air.

  • Panel Filter – gives only minimum reduced efficiency filtration.

Air Handler Coil

The coils are the reason for the supply of warm or cool heat inside your home. The evaporator coil is installed inside the compartment of the blower or air handler.

This coil is responsible for holding the chilled refrigerant that the compressor moves onto. 

The cold refrigerant moves the indoor heat as the air from the blower fans moves over the coil.

When the refrigerant becomes warm, it then travels to the condenser coil to be released outdoors.

The process is reversed during cold climates with a heat pump. Instead of releasing the warm air, the evaporator coil will expel the refrigerant’s heat into your home.

Chilled Water Valve

The chilled water valve will control the amount of chilled water flow from the coil.

The valve will get even colder when there’s a higher amount of chilled water flowing through the coil.

A particular electronic actuator usually controls these valves. The electronic actuator, depending on the temperature needed indoors, will open or close.

If the indoors are warm, it will open the valves to allow more chilled water movement through the coil.

If the indoors are cool, it will close the valves to reduce the amount of chilled water through the coil.

Air Handler Fan

The fan is in charge of moving air across the air handler. It is known to be the “heart” of every air handling unit since its purpose is to circulate the air through the air handlers.

The widely used air handler fans are the centrifugal fans.

The centrifugal fans can generate high air pressure needed for air distribution to a remote location.

This fan has almost the same appearance as a hamster wheel. Thus some refer to it as “squirrel cage fans.” It is driven by a belt attached to the motor.

The blower motor and the fan are usually placed on the vibration isolator to lessen the effect of vibration on the panel.

The speed of an air handler fan will vary on the frequency inverter used.

A frequency inverter delivers better control on the fan’s speed from super low to super high.

This technological advancement has created a better use of energy and has been in sync with greener energy.

Air Handler Blower Motor

The blower is the component that releases the cooled air back into your home through the ventilation duct system.

The air is moved to the connected ductwork that will circulate your home. The blower motor has three different speeds, a single-speed, multi-speed, and variable speed model.

  • Single-speed motor – The single-speed motor could only operate at one, fixed speed. As a requirement by a thermostat or control system, the motors in a single-speed are cycled on and off. This motor speed starts whenever the thermostat stipulates that the indoor space needs more heating or cooling.

  • Multi-speed motor – The multi-speed motor can operate at multiple speeds at a time. It may also run at full capacity speed or 100% speed to reach the high-demand thermostat or control system setting.

    Lower demand will automatically reduce the speed of the blower motor. The lower-stage demand provides reduced levels of humidity, supportable comfort, and consumes less energy than a single-stage system.

  • Variable-speed motor – Variable speed motor will vary the fan speed to reach a precise control of heated or cooled air indoors. This speed can give you more control of your indoor humidity levels and help you maintain a consistent home temperature.


Air handlers assimilate with ductwork designed to a specific model. The ductwork is also a vital component of an air handling unit. The reason for this is its purpose of circulating the air in and out of the AHU.

It is considered as the pipe connecting the space that needs conditioning to the air handlers. Good ductwork is made out of sheet metal that is rigid and can maintain its shape for a period.

Air Damper

The air damper controls the amount of airflow going through the air handler. It is usually installed on the outer side of the air intake of the air handler.

It is also responsible for the control of outside air entering the air handlers.

The air damper can also be installed on the return air intake and supply air ductwork. It will balance the amount of air entering and exiting the air handlers.

Professional HVAC specialists adjust the air dumpers to test and balance the start-up of the air handler.

Air Handler Mixing Box

The air handler’s mixing box has inlets of air attached to the dampers. It is where the return air and outside air are mixed to give the precise air distribution that needs conditioning. 

Types Of Air Handlers

Draw-Through Air Handlers

A draw-through air handler works by a fan pulling the air through a mixing box, filters, and cooling coil.

The air should be pulled through those components before being discharged from the fan outlet to the indoors. Once the air has been pulled, it will now be discharged and will be conditioned.

The draw-through air handlers are usually designed vertically or horizontally.

Blow-Through Air Handlers

A blow-through air handler works by blowing the air through the mixing box, filters, and cooling coil.

The airs should pass through those components to be conditioned before being discharged to the indoor space.

Air Handler Maintenance

Just like your other appliances, air handlers need constant checking and maintenance to ensure continuous air comfort.

  1. Disassemble your air handler unit, but make sure a licensed HVAC technician performs this procedure.

  2. Clean the air handler unit using a vacuum and antibacterial/antimicrobial solutions.

  3. Put the air handler unit all together again using a new insulated duct board and secure with aluminum tape.

Make sure to replace your air filters at least once a year.

You can also use this checklist for your regular air handler maintenance:

  • Check for noise and vibration of the air handler unit
  • Drain and clean condensation pan
  • Clean the filters
  • Lubricate the motor with grease and blower bearing
  • Check the bypass valve
  • Check for any loose wiring or wire damage
  • Carefully straighten coils


An air handler is an integral part of any air conditioning system since it circulates the air in your homes.

The air handler not only circulates air but ensures its safety from airborne disease and contaminants. 

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