What Does an Air Handler Unit Do?

large air handler unit

Your commercial HVAC system is made up of a number of interconnected sub-systems and parts. One of the most important components of your HVAC system is called the Air Handler Unit, or AHU. The AHU is the internal partner to the Condensing Unit, which is the big metal box outside your business or on the roof with the fan. Here’s how they work together to cool your home and business.

Basically, an HVAC system works to shift heat from inside your building to the outside. The first law of thermodynamics states that heat energy can neither be created nor destroyed; rather, it must be moved outside, where it can dissipate into the air. 

That’s why a commercial HVAC system has components on both the inside and outside of your building: the inside Air Handler Unit pulls heat from the air as it’s forced through the ducts and transfers it to the refrigerant, a special chemical which can absorb and release heat effectively. The now hot refrigerant, in gaseous form, travels through a refrigerant line to the Condensing Unit, which allows the refrigerant to radiate its heat to the outside air, condensing into a liquid in the process. Then, the refrigerant cycles back inside to get heated again.

Air Handler Anatomy

Air filter

Before the air in your building enters the Air Handler Unit, it needs to be cleaned to remove contaminants that can gum up the works. The air filter, which sits between the fan and intake ducting, does this important job.

Evaporator Coils

Once through the filter, the air passes over the evaporate (or indoor) coils. These coils contain refrigerant gas, which absorbs the extra heat latent in the air and cools it. If the Air Handler is the heart of your interior HVAC system, this is the heart of your Air Handler.


After the air is cooled (or “conditioned,” as in “air conditioner”), the blower fan within the Air Handler circulates it out of the Air Handler and into the ductwork, whence it is distributed throughout your office, warehouse, or factory as cool, conditioned air.

Why is an Air Handler Unit important?

The AHU, when coupled with the outdoor Condenser Unit, is the part of your HVAC unit that actually serves to cool the air circulating through your building. If the AHU doesn’t exist or fails, your commercial building basically just has an expensive fan system blowing tepid air around. That’s why regular maintenance and upkeep of your HVAC system is vitally important to the continued functioning of the system, and indirectly the functioning of your business as a whole.

Modern HVAC systems do more than cool the air. They also filter the air of contaminants like common allergens, air-borne pathogens, and toxins, keeping the air quality in your business high. A well-functioning HVAC system is also more efficient, which saves you money month-to-month in your utility bills.

The AHU helps keep the entire process of capturing excess heat from inside your building and circulating it outside energy efficient and effective. In addition, AHUs are highly important to the safety of your building. 

Irregular circulation within your HVAC system can cause frost that can damage equipment, leading to excessive condensation inside the building. Extra liquid can pool on the floor, causing slippage, or can short important electrical equipment. A properly working HVAC system requires a floor drain or condensation box to keep everyone who works for you safe.

The Takeaway

Unless you’re an HVAC technician, you probably only think about your HVAC system when it fails. However, a properly-working HVAC system is key to keeping the temperature inside your building safely regulated, which keeps your employees happy and healthy, and saves you money on your utility bills. Make sure to keep your entire HVAC system, especially the Air Handler Unit, properly serviced and cleaned.

You need a well-designed Air Handler Unit to help your HVAC system perform optimally. At Safe Air Technology, our expert HVAC engineers can design and build certified explosion-proof Air Handlers for your industrial needs. We can even customize your AHU to fit the size and shape of your operation. Contact us today to get started selecting or customizing an explosion-proof Air Handler today.