HVAC HVAC System Components

Understanding the different components that make up HVAC systems can make your life as a facility manager or property manager much easier.

Having the ability to quickly and correctly identify the component of your HVAC equipment that is causing a problem can positively affect the speed and efficiency in which your HVAC provider can get to work solving your problem.

There are two obvious instances in which knowing your HVAC system components will benefit you:


First, sending the correct person or team of people out to your location.

When your HVAC provider receives your service request the more information they have, the better. By providing your HVAC contractor with a detailed description of what the problem is and where you see the issue, they can better decide who to send out to your location based on the different skill sets of their technical team members and staff.

Second, arriving to your location with the proper tools and equipment to solve your problem.

Being prepared with the tools or in some situations replacement system components that are necessary to fix your HVAC equipment is a guaranteed way to make sure that your HVAC provider is using both your time and their time wisely.

Air Handler

An air handler is the indoor part of an air conditioner or heat pump that moves cooled or heated air throughout the ductwork.

An air handler is usually a furnace or a blower coil.


A compressor is the outdoor part of the air conditioner or heat pump that compresses and pumps refrigerant to meet cooling requirements.

Condenser Coil

The condenser coil is the outfoot portion of an air conditioner or heat pump that either releases or collects heat, depending on the time of year.

Evaporator Coil

The evaporator coil is the part of the air conditioner or heat pump that is located inside the air handler.

The primary function of the evaporator coil is to absorb heat from the air.


TXV stands for Thermo Expansion Device. The TXV meters the refrigerant from high pressure to low pressure based on the suction pressure and temperature, controlling the amount of refrigerant that goes into the evaporator coil.

Refrigerant Lines

Refrigerant lines are two copper lines that connect the outdoor AC or heat pump to the indoor evaporator coil.

Discharge Line

The discharge line is the line between the compressor and the condensing coil. The discharge line carries the vapor.

Liquid Line

The liquid line is usually the smaller line coming off the condenser. The liquid line carries refrigerant to the metering device and flows towards the air handler.

Suction Line

The suction line is usually the larger of the two lines going into the condenser. The suction line carries vapor from the evaporator coil to the compressor.


A contactor is a relay that is normally open, and when voltage is applied to the coil it closes, completing the circuit.

The contactor is normally found on the outside condensing units. The contactor supplies the power to the compressor, fan motor and electric heating systems.


The capacitor is a device that stores an electric charge and helps give a boost of power to motors and compressors.

In the HVAC field there are generally two types of capacitors, run capacitors and start capacitors.

Condensate Drain

The condensate drain is usually made of PVC, CPVC or copper.

The condensate drain leads the condensation out or into another main drain.

Drain pan

The drain pan is attached to the evaporator coil. This pan collects the condensation and then drains out through the condensate drain line.

Blower Assembly

The blower assembly is located inside of the air handler/furnace.

The blower assembly moves the blower wheel to move a volume of air in HVAC applications.

Blower Wheel

The blower wheel is attached to the blower motor.

If the blower wheel is dirty or has debris build up it can potentially restrict air flow or rotate out of balance.

Condenser Fan Motor

The condenser fan motor that has blades attached to move a volume of air.

In HVAC terms, the fan motor refers to the condensing unit while the blower motor refers to the air handlers.

Heat Exchanger

The heat exchanger transfers heat from one fluid to another without the fluids coming into direct contact with one another.

Heat Pump

The heat pump is an HVAC unit that heats or cools by moving heat.

In the Winter, a heat pump draws heat from outdoor air and circulates it through the air ducts.

In the Summer, it removes heat from the space and releases it outdoors.


The furnace is the place in the HVAC system where the heat transfer takes place when in heating mode.

Furnaces are typically in oil or gas systems.

Fan Coil

A fan coil unit is a unit that includes a cooling and/or heating coil and a fan to move air through the ductwork to a specific room.

Air Filters and accessories used to introduce outside ventilation air may also be included in the fan coil.


The thermostat is usually found on an inside wall. This device controls heating and cooling equipment, allowing simple adjustments of temperature and other comfort controls factors such as humidity and air flow.  

There are two types of thermostats: programmable and non-programable.

Programable Thermostat

A programmable thermostat is a thermostat with the ability to record different temperature and time settings for your heating and cooling equipment.


A non-programable thermostat is the simplest type of thermostat to operate and set up. This type of thermostat cannot be programmed to turn on and off at set days and times.


Ductwork is described as a square channel or round tube by which air is distributed from the air handler to the room.

Ductwork is used with Rooftop Units, Furnaces, Fan Coils and VAV Boxes.


A damper is a movable plate, located in the ductwork, that regulates airflow.

Dampers are used to direct air to the areas that need it most. They are typically used in zoning application. You can have manual dampers for air balancing.