How Do Air Handlers Work?
The air handler is the inside unit of your air conditioner or heat pump and in some homes it includes the gas furnace burner and heat exchanger. This system is essential to distributing heating and cooling air throughout your home all year long.
Understanding how your air handler works will help you know how important it is to properly maintain it. You’ll also be able to discern when problems are occurring that need attention such as troubleshooting and repair.
Let’s take a close look at how your air handler works and how to take care of it.
KEY TAKEAWAYS
- Air handlers are integral components of HVAC systems, responsible for circulating heated or cooled air through a home's ductwork. They work with central air conditioners, heat pumps, and gas furnaces, incorporating components like blowers, air filters, heat exchangers and evaporator coils to ensure efficient air distribution and temperature control.
- Proper maintenance of air handlers is critical for energy efficiency, consistent comfort, and system longevity. Regular tasks include changing air filters, cleaning blower components, and ensuring condensate drains remain unclogged. Neglecting maintenance can lead to uneven temperatures, higher energy costs, and potential system failures.
- Recognizing and addressing common air handler problems—such as fan failure, weak airflow, or unusual noises—can prevent costly repairs. Steps like checking circuit breakers, clearing clogged drains, and inspecting filters and ductwork can resolve many issues. Persistent problems often require professional HVAC service.
What Is an Air Handler?
An air handler is a central component of your HVAC system. It houses key parts such as the blower, air filter, and the evaporator coil. If you have a gas furnace, it houses the gas burner and heat exchanger. The air handler is the essential part of your heating and cooling system responsible for circulating air throughout your home’s ductwork.
Although the air handler works in conjunction with different HVAC systems—like central air conditioners, heat pumps, and gas furnaces—its fundamental purpose remains the same: moving air. Let’s break down how it interacts with each type of system.
Air Handlers in Central Air Conditioners
In a central air conditioner, the air handler typically contains the evaporator coil and a powerful blower. Here’s how it works:
Evaporator Coil Does the Cooling
The refrigerant, cooled by the outdoor condenser unit, flows into the evaporator coil inside the air handler. Warm air from your home passes over the coil, and the refrigerant absorbs the heat, leaving the air cool and comfortable.
Blower Circulates the Air
The blower fan pushes the cooled air into the ductwork, distributing it throughout your home. Meanwhile, the refrigerant carries the absorbed heat back to the outdoor condenser, where it releases the heat.
Air is drawn back into the evaporator through the return vents and air filter. The air filter screens out dust, pollen and other airborne contaminants from the circulating air.
Draining Condensate Water
The air conditioner evaporator dehumidifies your home by collecting moisture from the circulating air on its cooling fins in the form of frost.
When the cooling system thermostat cycles the compressor off because the set indoor temperature has been reached, frost melts from the evaporator cooling fins and drips down into a collection tray below the evaporator. That condensate water then drains to the outside of your home.
This cooling system relies heavily on the air handler’s efficiency. A dirty blower or clogged air filter can hinder airflow, reducing comfort and increasing energy bills.
Air Handlers and Heat Pumps
Heat pumps stand out because they can heat and cool your home using the same sealed refrigerant system. Electric heat pumps have an auxiliary heating element to support the heating system with additional heat when the sealed system isn’t able to provide enough heat during extremely cold weather.
Some heat pumps use a gas furnace as the back-up source of heat during severely cold weather.
The air handler works in the heat pump system to circulate both cooling and heating air.
Cooling Mode
The heat pump works the same as a central air conditioner in the cooling mode. The air handler’s evaporator coil and blower function exactly as described above. The cooling system dehumidifies your home and condensate water from that dehumidification drains to the outside of your home.
Heating Mode
When in heating mode, the heat pump reverses the flow of refrigerant so the hot refrigerant gas coming out of the compressor flows through the evaporator and circulating air absorbs heat from the refrigerant.
The air handler’s blower fan circulates the heated air throughout your home and draws the air back into the unit through return vents and the air filter.
After circulating through the evaporator, the refrigerant travels through the condenser coils in the unit outside your home where it pulls heat from the outdoor air (even in cold weather). The refrigerant then returns to the compressor and the heating cycle starts over. The compressor compresses the refrigerant into hot gas that travels through the evaporator to heat the inside air.
Because heat pumps depend on the air handler year-round, maintaining it is even more critical.
Air Handlers in Gas Furnaces
Gas furnaces use a different system for heating, but the air handler is just as important. In this setup:
The Furnace Burner Heats Air in the Heat Exchanger
The furnace’s burner ignites gas, creating heat. This heat warms the heat exchanger, a metal component designed to transfer heat to the air safely.
The Air Handler Blower Fan Moves the Warm Air
The blower fan in the air handler pulls air from your home through the return vents and air filter then pushes it through the hot heat exchanger. This heated air then travels throughout the ductwork and into your living spaces.
Unlike air conditioners or heat pumps, gas furnaces don’t require an evaporator coil inside the air handler. However, the air handler still contains the blower, air filter, and controls that keep the system running smoothly.
The air handler in some home heating and cooling systems houses both the furnace and the evaporator. The air conditioner or heat pump shares the furnace’s indoor blower fan.
Why Proper Air Handler Maintenance Matters
Because the air handler plays a role in every season, keeping it in top condition is essential. Neglecting the air handler can lead to problems like uneven temperatures, higher energy bills, and system breakdowns. Here’s how to keep it running efficiently:
Change the Air Filter Regularly
The air filter traps dust, pollen, pet dander, mold spores, and other airborne contaminants. It’s important to replace the air filter regularly for the following reasons:
- Improved Air Quality: A clogged filter is less effective, allowing dust particles, pollen and air contaminants to circulate through your home, which can exacerbate allergies and respiratory issues.
- Enhanced HVAC Efficiency: A clean air filter allows air to flow freely through the system. When the filter is clogged, the HVAC system has to work harder to maintain airflow, consuming more energy and increasing utility bills.
- Prolonged System Lifespan: Restricted airflow due to a dirty filter puts unnecessary strain on the HVAC system's components, such as the fan and motor. Over time, this can lead to wear and tear and potential system breakdowns, reducing the system's overall lifespan.
- Cost Savings: Regularly replacing the air filter helps avoid costly repairs and reduces energy consumption. It also prevents the need for more frequent maintenance due to clogged or damaged components.
- Consistent Comfort: A clean filter ensures that your HVAC system operates efficiently, providing consistent heating and cooling throughout your home. A dirty filter can result in uneven temperatures and reduced comfort.
- Prevention of Ice Formation: In air conditioning systems and heat pumps, a clogged filter can cause the evaporator coils to freeze due to restricted airflow, leading to system inefficiency or failure.
Most filters should be replaced every 1–3 months, but the exact timing depends on factors such as filter type, household size, number of pets, and whether anyone in the home has allergies or respiratory issues.
Regular air filter replacement is a simple, cost-effective way to maintain a healthy indoor environment and keep your air handler and entire HVAC system running smoothly.
Clean the Air Handler Blower Components
Dust buildup can throw the fan out of balance, reducing its lifespan and performance.
To clean the blower fan, shut off the house circuit breakers and remove the blower fan access panel. Clean fan blades using a vacuum cleaner with a brush attachment. Be careful not to bend or damage the blower fan blades.
Reinstall the access panel and reset the house circuit breakers to restore power to the system.
If you’re not confident that you can safely complete this maintenance step on your own, schedule HVAC maintenance and cleaning service. We’ll send a Sears Home Services technician to your home to clean, inspect and tune up your entire heating and cooling system.
Pour Bleach or Vinegar Down the Condensate Drain Stand Pipe
For air conditioners and heat pumps, the air handler includes a drain system for the condensate that drips from the evaporator.
To prevent the drain pipe from clogging up with algae and sometimes snails, shut off the system and pour a cup of liquid bleach or vinegar down the standpipe.
Repeat this maintenance step monthly to keep the condensate drain pipe clear.
Schedule Regular HVAC System Tune-Ups
Professional HVAC maintenance ensures that the evaporator coil, blower, and other heating and cooling system components stay clean and functional.
Recognizing and Troubleshooting Air Handler Problems
Watch for these symptoms of air handler problems and take the appropriate troubleshooting steps to resolve the issues:
Air Handler Fan Not Running
When you discover that the air handler motor isn’t running, follow these troubleshooting steps:
1. Check the House Circuit Breakers for the Indoor Unit
Reset the house circuit breakers if you find them tripped. This can restore power to the air handler blower motor so it begins running.
Monitor the system and if the circuit breakers continue to trip, schedule HVAC repair to have a service technician examine and repair the problem causing the breakers to trip.
2. Check the Condensate Drain System
Heat pumps and central air conditioner systems use a condensate drain float switch to detect when the drain pipe is clogged and condensate drain water is backing up in the drain tray below the evaporator.
If condensate water backs up and trips that float switch, the blower motor won’t run.
Check for a clogged condensate drain and clear it as shown in this helpful YouTube video:
With hundreds of thousands of views and according to testimonials in this video’s comments, this troubleshooting tips has restored cooling to thousands of homes.
This is one of the most frequent causes of air handler problems so keep this tip in mind when you find the indoor blower motor not running during the summer.
Fan Motor or System Failure
If the above troubleshooting tips don’t help, HVAC system problems such as a bad blower motor, control problems or a wiring failure can be preventing the air handler blower fan from running. Interlock switches, inducer fan problems and other issues can prevent the blower fan from running in a gas furnace.
In this situation, you’ll likely to schedule HVAC repair service to find and fix the problem that is preventing the blower fan from running.
Weak Air Flow
When the blower motor runs but you notice weak airflow through the vents in your home, follow these troubleshooting steps:
- Check the air filter. A clogged air will inhibit air flow through the air handler and your home. Replace the air filter if you find it clogged with lint and dirt.
- Look for blocked return vents. If you have items stacked in front of return vents, move the items so air can flow freely through the return vents. Clean the vent cover louvers if they’re clogged with dust and dirt.
- Examine the ductwork. Look for leaking or disconnected ductwork that could be inhibiting airflow through the system. Reconnect any disconnected ductwork and repair any leaking or damaged ductwork.
If these basic troubleshooting tips don’t help, you’ll likely need to have a service technician diagnose and repair the problem.
Unusual Noises
Rattling or vibration noises could indicate that fasteners such as screws, nuts or bolts are loose inside the air handler unit.
Shut off the house circuit breakers for the air handler and check for loose fasteners. Tighten any fasteners that you find loose to eliminate the rattling or vibrating noise.
If you’re unable to find and fix the noise problem on your own, schedule HVAC service to have a service technician take care of the issue.
Understanding how the air handler works will help you recognize and troubleshoot air handler problems. It can also help you to know how to maintain your HVAC system’s performance and extend its lifespan.
With regular maintenance and prompt attention to issues, you can ensure a comfortable and energy-efficient home year-round.
Schedule your HVAC maintenance now!
HVAC checkups from Sears Home Services help keep your heating and cooling system running at its best. Prevent costly repairs and can make your HVAC system more energy efficient with routine maintenance.
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Glossary Terms
A humidifier is a device designed to increase humidity levels in a single room or an entire building, improving air quality and comfort.
Swamp cooling, also known as evaporative cooling, is a method that cools air through the natural process of water evaporation. It is energy-efficient and environmentally friendly, particularly effective in hot, dry climates.
Freon is a trade name for a group of chlorofluorocarbons (CFCs) used as refrigerants in air conditioning and refrigeration systems, known for its role in ozone depletion.
An inverter AC unit is an air conditioning system equipped with inverter technology that allows it to vary the compressor speed, enabling precise temperature control and increased energy efficiency.
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