How Does Air Handling Unit Work?

There are so many HVAC-related terms that, at one point, you might get a little confused.

Even though an air handling unit has a coil that can slightly cool the air before it enters the ductwork, an AHU and an air conditioner have completely different functions. The main job of the air handler is not to cool or heat the air, but to circulate it throughout your house.

How Does Air Handling Unit Work?

An air handling unit, or an AHU, is part of the HVAC system that is designed to circulate air throughout your house.

The air returns to the AHU via the ducts. This return air then moves into a special mixing box where it mixes with the outdoor air (some air handlers don’t use fresh air from the outdoors, they simply recirculate the air already present in the building).

Read: Why Does My Central Air Have Two Filters?

What Is the Difference Between an Air Conditioner and an Air Handler?

It is relatively easy to understand the difference between air conditioners and air handlers because the two units have different functions.

  • An air con takes the air from the outside, cools it, and then transfers it into the house. Air conditioners also move warm air over a coil that contains a special liquid that extracts the heat out of the air.
  • An air handler controls how the air moves throughout your house without cooling or heating it.

Do bear in mind that many AC units and heat pumps come with an air handler. The latter assists the unit in moving the heated or cooled air throughout the space.

Read: Does Air Handler Have Filter?

Where Are Air Handling Units Located?

Unlike air conditioners, air handlers are typically located inside the house. The units can be placed in attics, basements, or dedicated closets.

An air handler is a relatively large metal box that might look like a furnace. Ideally, you would want to place the unit as close to the center of your home as possible for the best performance.

Do Air Handling Units Use Water?

Hydronic air handling units do have water in them that flows through the coil. This medium can be used to transfer heat or cold to the air that travels over the coil.

The units that don’t have water use refrigerant.

What Are the Different Types of Air Handlers?

  • Horizontal and vertical units

Typically, vertical units require less floor space.

  • Draw-through and blow-through units

The location of the fan is what makes the air handler a blow-through or draw-through unit. The latter is the most common AHU.

  • Outdoor air (makeup air) or mixing units

Makeup air units use 100% outside air while mixing units (as the name suggests) can use a mixture of outdoor air and recirculating air.

  • Single-zone and multi-zone units

A multi-zone AHU is often used for dual-duct systems.

  • Rooftop and indoor units

There are special air handlers that are designed for outdoor use. They are usually mounted on the roof and are corrosion-resistant.

However, the majority of AHU are indoor units.

  • Custom-built and field-built units

Standard units are less expensive and can be delivered in the shortest timeframe. Custom-built air handlers offer more flexibility and can be designed to be the most energy-efficient fit for your house.

Read: Does HVAC Purify Air?

What Are the Components of Air Handling Unit?

Every air handler consists of quite a few important parts:

  1. Air intake – the component that draws in the air from the outside or recirculates the indoor air.
  2. Filter – the majority of air handlers have a filter that you would have to change on a regular basis.
  3. Blower/fan – the component that moves the air from the air handler into the ducts.
  4. Heating and/or cooling elements – the air handler can change the supply air temperature if it has heat exchanger coils.
  5. Silencer/vibration isolators – the blower can create a lot of noise. These components help make sure that the noise and vibration levels are not unbearable.
  6. Mixing plenum – a compartment where the return air and the supply air get mixed together before passing through the rest of the unit.

Does an Air Handling Unit Have a Compressor?

Air conditioning systems can consist of an air handler and a condenser.

The condenser is the outdoor unit that is responsible for releasing warm air into the outside environment. The condensing unit is the part of the system that houses the compressor.

It is important for the compressor to be located in the outdoor unit as the component raises the pressure of the refrigerant and sends it to the condensing coils. This is what makes the heat escape into the outside air.

Read: How To Reduce Dust With Forced Air Heat?

Do Air Handling Units Have Refrigerant?

An AHU can have refrigerant inside its coils. Thanks to the liquid, the air handler is able to slightly cool the air that passes through it.

These are direct heat exchangers. Indirect heat exchangers use water or steam to condition the air.

Do You Need an Air Handler?

Air handlers are commonly used in conjunction with heat pumps and air conditioners. If you have a furnace, you wouldn’t have to worry about getting an AHU.

When it comes to air cons, the air handler will take care of the ‘ventilating’ part of the process and the unit can remove some additional heat from the supply air thanks to its own evaporator coil.

Heating elements can also be included in an air handler. Electric heating strips, for example, can become the source of auxiliary heat, in case you have a heat pump.

Air handlers can bring a lot of benefits in warm and mildly cool climates. However, pairing a heat pump with an AHU in a cold climate might not be efficient, as such a combo may not be able to keep your house warm when it’s extremely cold outside.

Read: What Is Heat Pump? Everything You Need To Know

How Much Does an Air Handler Cost?

Hydronic air handlers cost between $600 and $3.500. The price of a variable-speed unit ranges from $1.000 to around $3.500.

The price of the air handler is going to depend not only on the type but also on the size. A 3-ton unit is among the most common ones and will cost you $700-$1.500 for a regular unit.

Be prepared to pay anywhere between $200 and $2.100 for the installation of an AHU.

The price will depend on the complexity of the project and the space where the unit would be installed (it usually costs a bit more to install the AHU in the closet).

Some additional installation cost factors might include ductwork repair or replacement, installation of new electric wiring, and so on.

How Long Do Air Handlers Last?

In general, an AHU will last you 10-15 years. To prolong the life of your heating and cooling equipment, you have to make sure that the whole system undergoes annual maintenance.

How Do You Clean an Air Handling Unit?

The cleaning of an AHU includes:

  • Cleaning of coils/drainage/fan
  • Inspection of drain tubes
  • Cleaning of the interior chambers
  • Removal of old filters and the cleaning of the racks

It is better to let the professionals take care of your air handler. What you can do on your own is change the unit’s filter. You will find the filter on the side of the unit, on the top of the air handler, or below it. Check the filter every month or so and change the thing, if it looks dirty (usually, every 90 days).