How Does an Air Handler Work?

If there is a heat pump outside a house, then there is likely an air handler somewhere inside. Air handlers are best described as air distribution systems and are most often found in basements, attics or dedicated closets. This system looks very similar to a gas furnace — so much, in fact, that many people mistake it for one. This guide explains the components of this system, how it works and what size is best for your home or business, then shares some handy maintenance tips.

What Is an Air Handler?

Think of an air handler as your home's lungs. Air handlers don't heat or cool the air, but together with heating and cooling equipment, they handle the flow of air that keeps your house clean and comfortable all year round. The cabinet of the air handler contains some indoor components of the HVAC system, as well as some additional items that serve to improve ventilation and indoor air quality, such as electronic air filters, ultraviolet (UV) light and dehumidifiers.

Components and Parts of an Air Handler

An air handler generally contains the following components:

1. Blower motor. This motor pushes air through your ductwork, allowing it to circulate throughout your house. Various types of motors are available in air handlers, including single- and multi-speed motors, which run at fixed revolutions per minute (RPMs) and are designed to move a consistent amount of cubic feet of air per minute. Variable speed motors, on the other hand, adjust their output based on the conditions they monitor, thereby maximizing efficiency. A variable speed motor is also sometimes referred to as an Electronically Commutated Motor (ECM).

2. Plenum connectors. Plenum connectors are boxes that connect your supply and return ducts to your air handler. Supply ducts carry the cooled or heated air to vents, which are also known as terminal registers, in each of your home's rooms after the air has traveled through your filter and air handler. Return ducts are responsible for bringing unconditioned air from each of the rooms back into your system, where it will then be filtered and conditioned once more.

3. Air filter. When unconditioned air is brought into the air handler, it passes through a filter. This is because this air can contain dirt, debris and other particulates that could cause damage to internal components of the air handler. The filter serves to protect these components by capturing any incoming particulates.

4. Evaporator coil. The evaporator coil enables heat energy to be removed from or added to the indoor air. In an instance where the air is being cooled, refrigerant, which is located in the air conditioning unit outside, is pumped in in the form of a high-pressure, high-temperature gas, where a valve then converts the refrigerant into a low-pressure, low-temperature gas. This gas is then pumped into the evaporator coils, and when air passes around these coils, heat energy transfers from the air to the refrigerant, thereby cooling the air. This cooled air then continues on out through the supply ducts. The refrigerant in the coils, which now contains heat energy, is then pumped back out to the outside unit again, where the cycle continues.

5. Electric heat strips. Some air handlers are also equipped with electric heat strips, which use electricity to provide additional warmth when needed. They can be used with both AC-only systems as well as with heat pumps when it gets too cold.

It is important to note that the components of air handlers vary from region to region and from manufacturer to manufacturer. The parts we've described above are found in typical air conditioner/heat pump setups.

How Does an Air Handler Work?

Your air handler circulates conditioned, filtered air through your home in four basic steps. In this section, we'll explain each step that an air handler goes through to circulate air through your home. They are as follows:

1. The air handler pulls the air in. Return air, which is air coming back through the return vents, is pulled into the air handler, where it is then filtered.

2. The air is filtered. Air traveling through ductwork can carry contaminants that can damage the internal components of the air handler, as well as cause those in the house to become sick. This is why the air first passes through an air filter, where airborne contaminants like dirt, hair and pet dander are captured, allowing only clean air to pass through to the coils. Change this filter frequently to ensure that the air stays as clean as possible and can flow more smoothly. You should change the filter at least once a year or, if you have pets, allergies or asthma, even more frequently. Consult your owner's manual regarding the recommended frequency for your unit.

3. The air passes through the coils. Once the filter has cleaned the air, it then passes through the evaporator coils, where it is heated or cooled. In either case, the refrigerant is pumped into the coils from the outside unit. If the air is being cooled, the refrigerant will be a high-pressure, high-temperature gas, and a valve will convert it into a low-pressure, low-temperature gas, which then goes into the evaporator coils. When the air passes between these coils, the air is cooled. The refrigerant then makes its way back outside, where the cycle starts over.

4. The air is blown out: Once the air has been conditioned, the blower pushes the air through the supply ducts until it reaches the vents throughout the house, delivering conditioned, filtered air to your living areas.

What Size Air Handler Do I Need?

An air handler's size is directly related to the size of the condensing unit. To determine the size of the air handler that your application requires, follow the steps below:

1. Determine the required size of your condenser unit. Call an engineer and have them perform a load calculation for your home. This will determine the tons per square feet that the condenser must be capable of handling. Typically, one ton is required for every 500 square feet.

2. Determine the required size of your air handler. Your air handler size depends on the size of the condenser unit. So if the air condenser must be 4 tons, then the air handler must be 4 tons, too. The air handler can be larger than the condenser unit by up to 1 ton, but the better you can match the sizes, the better the performance will be.

3. Make sure you have the electrical capacity. Some air handlers require more energy than others. Find out the energy requirements of your unit and confirm that your electrical setup is capable of supporting it. If you have insufficient capacity, then you have two choices: either redo your electrical connections or resize your air condenser and air handlers to the largest size that your current electrical connections can support. You can check the electrical capacity by viewing the circuit breaker panel. On the panel, look for the air handlers, and beside it should be its maximum rating. Compare this rating to the electrical requirements of your air handler, which you should be able to find in the air handler's manual.

Air Handlers vs. Furnaces

As air handlers and furnaces are often mistaken for one another, it's not uncommon for people to wonder what the difference is. Luckily, this question has a straightforward answer. Let's start by discussing how the two systems are similar:

• Exterior appearance. Air handlers look just like furnaces on the exterior. After all, they're both big, metal cabinets. This is why people often confuse the two.

• Purpose. They both condition and circulate the air that travels through a house.

Air handlers and furnaces differ in the following ways:

• Heating components. Air handlers, unlike furnaces, lack burners, heat exchangers and other heating components found in furnaces.

• Source of functioning. As air handlers do not contain burners to heat the air like furnaces do, this means they cannot run on propane or natural gas. They instead run on electricity.

• Ventilation of exhaust air. As air handlers are all-electric, they do not produce exhaust, meaning that no ventilation system is required.

Air Handler Maintenance

Even the highest-quality air handlers will need some maintenance from time to time. To make sure your air handler is working reliably and efficiently, we recommend that you routinely perform the following tasks. Of course, if you notice a problem, it is important to contact your HVAC professional right away.

• Air filter maintenance. Air filter maintenance is absolutely essential for your air handler, so make sure to change it if it's disposable or clean it if it's a semi-permanent filter at least once per year. If you own pets or suffer from asthma or seasonal allergies, you should do this more frequently. A sudden drop in air quality for any reason is also a good reason to change your air filter. If you do not routinely replace your filters, this can lead to debris and mold accumulation, which can restrict the air streams. Left untreated, debris and dirt can attach themselves to the blades of the fan as well as the motor, which can lead to even more serious problems. Mold accumulation can also endanger the health of those in your household.

• Listen for any usual sounds. Always be listening for strange or excessive noises or vibrations. If any of these strange noises persist, call your HVAC professional.

• Be aware of unusual smells. If you smell something musty, this could mean that mold is growing inside the air handler. If you notice a burning smell, this could mean there's an electrical issue with the motor. Inform your HVAC technician of these issues immediately.

• Have your air handler regularly serviced. Make sure you have a professional periodically inspect your system. This route maintenance will include straightening coils, inspecting the wiring and cleaning the condensate drain and coils. How often you need to have it inspected depends on your usage and the type of system you have. Consult the owner's manual to find out how frequently you should service your unit.

• Set the temperature when you're away. If you're leaving your home for several days, or if the temperatures outside are comfortable, set the temperature inside so your system doesn't run unnecessarily. When you get back home, or when the temperatures dictate, reset your system, and the air in your home will immediately become comfortable once again. Keep in mind that, if you live in a cold climate, you need to keep the heat on or take other precautions to prevent your home's water pipes from freezing and bursting. We suggest that you set your thermostat to around 85 degrees F in the summertime and lower your thermostat to 55 degrees F in the wintertime.

Replacing Your Filter

As mentioned above, cleaning out or replacing your filter is perhaps the single most important thing you can do when it comes to air handler maintenance. Here are the four simple steps for replacing an old air filter:

1. Locate and remove the old filter. Your air handler filter is often located behind your indoor unit's bottom panel. In some cases, there may be more than one filter.

2. Acquire a compatible replacement filter. Your replacement filter should ideally be the same make and model as the original filter, and at the very least, it must be the same type and size as the one originally supplied.

3. Correctly orient the new filter. On the filter, you'll notice that there are arrows on it. Position the filter so that the arrows are pointing in the same direction as the air flow.

4. Insert the new filter. Make sure that your new filter is properly inserted. When you're done, sit back and breathe in the fresher air!

We should note that the above steps apply only to disposable filters. If you have a semi-permanent air filter, then it is not meant to be replaced, but rather cleaned. In this case, just remove it from the frame and vacuum it.

I Need a New Air Handler.

After reading through this article, you may have started thinking that you need a new air handler so you can maximize your comfort. The best place to start looking is right here, at Ingrams Water and Air!