When Northwest Indiana temperatures swing from blistering summer heat to freezing winter snow, you rely heavily on your HVAC system. While most homeowners are intimately familiar with their air conditioner, furnace, and thermostat, there is one critical component quietly doing the heavy lifting behind the scenes: the air handler.
But what is an air handler, exactly? And if you already have an AC unit outside, why do you need another piece of equipment inside?
If you are upgrading your HVAC system or trying to troubleshoot airflow issues, understanding this crucial component is the first step. Here is everything you need to know about air handlers, how they work, and why they are essential for your home’s comfort.
What Is an Air Handler?
At its simplest, an air handler (often abbreviated as AHU, or Air Handling Unit) is the indoor component of a split HVAC system. While it typically looks like a large metal box resembling a furnace, it does not actually generate its own heat or cold air.
Instead, an air handler is the circulation powerhouse of your home. It houses the critical internal components that push conditioned air through your ductwork and into your living spaces.
Inside a typical residential air handler, you will find:
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The Air Filter:
This is the primary defense against airborne contaminants. It traps dust, dander, and allergens before they enter the system.
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The Evaporator Coil:
This is the a-shaped component where the actual cooling (or heating, if paired with a heat pump) takes place via indoor refrigerant lines.
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The Centrifugal Fan (The “Squirrel Cage”):
This is the powerful blower motor responsible for physically moving the air. It gets its nickname because the cylindrical arrangement of the fan blades looks just like a hamster or squirrel wheel!
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The Control Board:
While not pictured in the airflow diagram, this electronic brain sits just behind the metal casing to regulate fan speeds and communicate with your thermostat.
What Does an Air Handler Do?
If the outdoor compressor is the heart of your HVAC system, the air handler is the lungs. So, what does an air handler do daily? Its primary job is to ensure that treated air moves efficiently, quietly, and evenly throughout your entire home.
Here is the step-by-step process of how it works:
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Pulling Air In:
The air handler’s blower motor pulls unconditioned, stale air from inside your home through your return vents.
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Filtration:
Before the air is treated, it is forced through the air filter to remove dust and debris, protecting both the equipment and your lungs.
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Conditioning:
The clean air passes over the evaporator coil. If it’s a hot Schererville summer, the cold coil removes heat and humidity from the air. If you are using a heat pump in the winter, the coil transfers warmth into the air.
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Distribution:
Finally, the blower pushes the newly conditioned air out through your supply ducts, delivering perfect comfort to every room in the house.
This continuous cycle is what maintains your home’s target temperature and indoor air quality.
Air Handler vs. Furnace: What is the Difference?
This is the most common point of confusion for homeowners. Because they are both large metal boxes connected to your ductwork, it is easy to mix them up. However, the difference comes down to how they treat the air.
A Furnace actively generates heat by burning fuel (like natural gas or propane) or using heavy-duty electrical resistance coils. It has its own blower motor to push that freshly generated heat into your home.
An Air Handler does not generate heat. It only moves air that has been heated or cooled by another piece of equipment, most commonly an outdoor heat pump or central air conditioner.
Do I have both?
If you have a traditional gas furnace and a standard air conditioner, your furnace actually acts as the air handler during the summer, using its blower motor to push the AC’s cold air through the house. However, if your home relies entirely on an electric heat pump for both heating and cooling, you will have a dedicated air handler inside rather than a furnace.
Choosing the Right Air Handler for Your Indiana Home
Not all air handlers are created equal. The type of blower motor inside your unit drastically impacts your home’s comfort, humidity levels, and monthly energy bills.
The most common types of air handlers are:
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Single-Speed Air Handlers:
The most basic and affordable option. The motor is either 100% on or 100% off. While reliable, they can cause noticeable temperature swings and are less effective at managing Northwest Indiana’s heavy summer humidity.
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Multi-Speed Air Handlers:
These units can step their speed up or down depending on your home’s demand, offering better energy efficiency and improved humidity control compared to single-speed models.
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Variable-Speed Air Handlers:
The absolute gold standard for home comfort. Variable-speed motors constantly make micro-adjustments to their speed. They can run at a very low, continuous hum, which perfectly balances the temperature in every room, operates in near silence, and offers superior dehumidification and air filtration.
How Siemer Helps You Make the Right Choice
At Siemer Heating, Cooling & Plumbing, we don’t believe in a one-size-fits-all approach, and we certainly don’t just point you toward the most expensive box.
When our technicians evaluate your home, we use this exact criteria to find your perfect match. We look at your home’s square footage, the layout of your existing ductwork, and your specific comfort goals, whether that is finally conquering the muggy humidity on your second floor or drastically lowering your winter utility bills. We walk you through the pros, cons, and upfront costs of each tier so you can make an educated, pressure-free decision that fits your family’s budget.
Learn more about our air handler services. Then, contact us to schedule yours.