HVAC Types of HVAC Systems
Air Handlers (AHU)

Air handler is a term commonly referencing any unit that has an indoor fan circulating airflow through a duct system.

An air handler can range from a very small unit, have a refrigeration-based DX coil to an extremely large chilled water coil


DX Coil

A DX coil is the indoor part of a split system using refrigerant, not water to transfer heat from the air.

In almost all air handlers, there are filters to protect the coil from dirt and debris on the airflow entering side. An internal fan pulls or pushes the air through the coil for the heat transfer to take place. The airflow exits through the space. As the air moves through the space, it warms again.


Package Units

A package unit is a single unit that consists of the evaporator coil, condensing coil, compressor, fan motor and blower motor all in one unit.

A package unit can be located on the ground or on the roof of a building. If located on the roof, a package unit can be downflow or horizontal flow, meaning the direction the air comes out of it from the indoor fan.

Package units are the most popular among commercial buildings.


Split & Mini Split Systems

A split system is a heating and cooling system that consists of an air handler or furnace and condenser.

A split system usually has the compressor and condenser in an outdoor unit, and the metering device and evaporator coil in the indoor unit.
(*link bold terms to blog post on HVAC system components)

A split system can be designed and configured to best fit a space. Both components of a split system are connected by a copper line set. The suction line and the liquid line.

A mini split system is a heating and cooling system that allows you to control the temperature in individual rooms or spaces.


Exhaust Fans

Exhaust fans are used to pull excess moisture and unwanted odors out of a particular room or area.

Exhaust fans are commonly found in bathrooms and kitchens, where moisture can build up.



Humidifiers maintain humidity in rooms that require a specified humidity range.



Chillers are commonly used in commercial applications and large buildings. Chillers use chilled water to transfer heat from the air handler or fan coil to complete the refrigeration cycle.

A chiller makes cold water, and it is pumped throughout a building to air handlers, allowing indoor fans to blow air across the chilled water coil, transferring heat from the warmer air to the colder water. The chiller then releases the heat to the condenser using refrigerant and the basic air conditioning process.


Cooling Towers

A cooling tower is a heat rejection device that removes heat from the hot water that is pumped from the condenser to the tower.

Warm condenser water will typically enter the top of the cooling tower, allowing it to flow through the media. The water separates and divides as the fan pulls cooler air through, absorbing the heat from water into the air and releasing it to the outdoors through evaporation.

The cooler water then cycles back into the condenser to reabsorb heat from the refrigerant.

When we use air with fan to cool the refrigerant it is referred to as and air-cooled chiller. When we use water to cool the refrigerant it is referred to as a water-cooled chiller.



Boilers are pressurized systems that burn combustible fuel or use electricity to heat water that is used to provide heating in a building.

Inside the boiler, the burners or electric coils generate heat that is transferred to the water by the heat exchanger. This process creates either hot water or steam, depending on the type of boiler. The hot water or steam is circulated via pipes throughout your facility. The water or steam enters radiators or other components that disperse heat needed to keep your spaces comfortable.

Some types of boilers use hot water itself, while others rely on water that has been turned to steam.