What Are the Components of an HVAC System and How Do They Function?

An HVAC system helps keep your home comfortable by heating and cooling the air circulating through it. Hoock’s Heating & Cooling provides HVAC installation services in Wentzville, O’Fallon, MO, and the surrounding areas. We can evaluate your needs and install a system that meets your desired comfort levels. Here are the main components of an HVAC system and how they work:

The Furnace

Furnaces handle the heating part of HVAC systems. A furnace can be powered by natural gas or propane. Its basic parts include a heat exchanger, a blower motor, and a combustion chamber. The combustion chamber safely burns fuel to generate heat while the heat exchanger transfers the heat by air passing through it. The blower motor pushes warm air into the ductwork and around your home. Our HVAC installation contractors can recommend the best unit for your needs.

The Air Conditioner (Condensing Unit)

When it’s hot outside, the air conditioner cools the air in your home. There are three main components. First is the compressor, which is the heart of the system. Its main function is to pump refrigerant through the system and compress it from a gas to a liquid. Next is the condensing coil. This is what receives the heat from inside your house and rejects it to the outside air. Lastly is the condenser fan motor. Its main job is to pull air through the condenser coil to assist in the heat transfer process.

Evaporator Coil

This is the indoor equipment that receives the liquid refrigerant from the compressor. When the refrigerant gets to the evaporator coil a metering device subcools the liquid into a gas. During this change of state, the gas travels through the evaporator coil, cooling the coil and absorbing the heat from your home. The cool air is disbursed into the home through the ductwork. During this process the coil also hits what’s known as dew point, allowing the system to pull humidity from inside your home. The gathered humidity is collected in the drain pan and routed to a drain via the drain hose. The hot gas absorbed from your home returns to the outside condensing unit to repeat the process.

Heat Pump

A heat pump is a combined heating and cooling system. There are two forms of heat pumps. The first is an air-to-air. In the summer, it works like an air conditioner to cool your home. During winter, it does the opposite and pulls in heat from the outside air to keep your home warm. It does so with a component called a reversing valve. The reversing valve reverses the flow of refrigerant allowing the evaporator coil to provide cool or warm air to the home.

The second style is a geothermal heat pump. This uses a series of loops in the ground or water source to absorb or reject heat. With a geothermal heat pump you only have one indoor piece of equipment. This style unit is known to be the most efficient option of all types of HVAC systems. Homeowners often chose a heat pump system to eliminate high energy costs produced from traditional electric resistance heat or propane heat. Hoock’s Heating & Cooling is reliable and knowledgeable in HVAC installation, and we can help determine if a heat pump is the right choice.

Air Handler

The air handler, commonly referred to as an electric furnace, is the indoor component most commonly installed in homes without a gas or propane heat source. An air handler is basic in design and is made up of three major components. An evaporator coil, blower motor, and electric resistance heat kit. Just as with a furnace, the blower motor pushes conditioned air through ductwork to different rooms in your home. The heat source for an air handler is the heat kit which uses electric resistance coils to provide heat to your home. This type of heat can be thought of as a giant hair dryer for your home. This source of heat is generally the most budget friendly to install, but the costliest to operate. To combat the operating cost of electric heat, we recommend pairing with an air-to-air heat pump.


Ducts distribute cold or hot air from a source throughout your home. They are usually made from sheet metal and can be insulated to reduce heat or cold transfer. Your HVAC installation contractor will design your ductwork system so that each room receives the right amount of heating and cooling. Your ducts should be inspected for any obstructions or leaks regularly, as these can reduce the efficiency of your system.


A thermostat controls your HVAC system. It allows you to set the temperature and determine when heating or cooling should turn on or off. Programmable thermostats are the most commonly used type and will allow you to set different temperatures at various times of the day. Smart thermostats are the latest type and can be controlled remotely through an app.

Contact Hoock’s Heating & Cooling for HVAC Installation

You need a reliable HVAC system to keep your home comfortable when it’s extremely hot or cold. At Hoock’s Heating & Cooling, an independent American Standard Heating & Air Conditioning dealer, we can assess your heating and cooling needs and install the ideal system. Modern models are more energy efficient, helping you save money on energy bills. We also offer repair and maintenance services for existing HVAC systems for optimum performance. Call (636) 266-2187 to schedule an appointment.