The difference between an air handler and a furnace is that a furnace creates and moves heat. An air handler moves air heated (or cooled) by another source.
Air handlers and furnaces are heating and cooling appliances that look very much alike. Their function is similar too.
In fact, in some ways they are more alike than different. We’ll go one step further and say that a furnace is a type of air handler with the added purpose of creating heat.
Let’s sort this out in FAQ fashion.
What is an Air Handler?
An air handler moves heated and cooled air in a forced-air system.
Forced air systems use a powerful fan called a blower to circulate air through your ductwork.
In short, the blower handles the air. The cabinet the blower is a part of was given the name “air handler,” which is quite fitting.
Here’s how the air handler functions.
1. The air handler blower circulates air in and out of ducts and grates.
2. The air handler contains the indoor coil that is essential to Heat and Air Conditioning modes.
AC Mode: The blower pulls warm, moist air into the air handler through ducts called return ducts. In the air handler, the air travels over the coil. The coil contains refrigerant that absorbs heat out of the air to effectively cool it.
As this happens, the coil gets very cold.
Moisture is condensed out of the air and onto the coil, drying it and making it more comfortable.
The blower pushes the cooler, drier air through ducts called supply ducts, through grates and into your living space.
The hot refrigerant travels to the AC or heat pump outside and into a radiator-like coil where the heat is transferred out of the refrigerant and dispersed.
Heat Mode: Heat pump systems use air handlers too. When heating, the physics are reversed.
Refrigerant captures heat outside and carries it indoors. When the refrigerant enters the coil in the air handler, it releases that heat. The coil gets very hot.
The blower pulls cool air into the air handler and over the coil. The air is heated and blown through the ducts into the rooms of your home.
What is a Furnace?
A furnace is an appliance that creates heat. There are three types of furnace.
- Gas furnaces are the most common.
- Oil furnaces are used mostly in the NE where natural gas isn’t readily available.
- Electric furnaces use electric resistance to create heat. They are the least efficient and should only be considered in a warm climate where it is used infrequently.
All furnaces have a blower fan, just like an air handler.
When the thermostat calls for heat, gas and oil furnaces start burning fuel.
An electric furnace will energize the heating coil, which is like a large space heater.
When the combustion box/heat exchanger or the electric coil gets hot, the blower starts. It pulls cool air into the furnace, heats it and pushes it out through the ducts and grates to warm your home.
When the temperature rises enough to meet the thermostat setting, the furnace stops making heat. The blower runs a little longer to push built-up heat out of the furnace.
What is the Difference Between an Air Handler and a Furnace?
The fact that a furnace creates heat and an air handler does not is the big difference.
That’s the main distinction.
1. A furnace is a heat source. An air handler is not.
An air handler distributes heat that is created by another appliance – a heat pump.
In the few locations of the US where heat is almost never needed, an air handler might be installed in a system with an AC rather than a heat pump.
There’s a second distinction that follows from the first.
2. All air handlers must contain a heat pump/AC coil. This is the corollary of them not making heat. They use the coil to distribute heat gathered outside.
Not all furnaces have a coil. If the system does not include central air conditioning, there is no need for a coil. If AC is part of the system, the furnace will contain a coil.
How Are an Air Handler and Furnace Similar?
As we’ve noted, they both contain a blower fan used to circulate heated and cooled air through your ductwork and grates.
Here are other similarities:
1. Single-speed and Variable-speed models are available. Single-speed blowers are used in single-stage furnaces and with single-stage heat pumps and air conditioners.
Variable speed blower motors are used in 2-stage and modulating furnaces and with 2-stage and modulating heat pumps.
2. All brands make them. Carrier, Trane, Goodman, Rheem, Lennox, etc. all make furnaces and air handlers. Furnaces are paired with ACs in split systems. Air handlers are paired with heat pumps or, in rare cases, just an AC.
3. The systems are controlled by a thermostat.
4. Different sizes are available. Blower size requirement is based on the airflow needs of the house.
- Size is definitely a factor. The larger the home, the bigger the furnace or air handler should be – the more CFM (cubic feet per minute) of air it should move.
- Ductwork must be considered too, regardless of house size. Bigger ducts need a bigger blower to create the right air pressure to effectively move air.
We strongly recommend hiring an HVAC technician to determine what size air handler/furnace blower is needed based on your home size and ductwork capacity.
Which is Better – an Air Handler or Furnace?
Of course, the real questions is what type of heat is best for your home.
In warm and hot climates, a heat pump and air handler system offers the lowest energy costs.
In colder climates, many heat pumps aren’t able to collect enough heat outdoors, so they become ineffective, inefficient or both. Furnaces remain a great option for cold climates.
What about both? A dual fuel system is one that contains both a heat pump and a furnace, with the furnace acting as the air handler for the heat pump. The heat pump does the heating when temperatures outside are above about 35F; the furnace heats the house in colder temperatures.
Here is a useful map from Trane. A gas furnace or dual fuel system should be used in the gray states. A heat pump is a suitable option for red states.