Air Conditioners: Understanding How the Central Cooling System Works

April 30, 2015

During the spring and summer, the air conditioner in your Des Moines home can keep you comfortable no matter what the temperature is outside. It takes many parts for the system to function, and this guide will help explain how an air conditioner works to keep you cool.


The compressor acts as a pump, helping to move the refrigerant through the air conditioning system, and it also compresses the refrigerant. The refrigerant enters the compressor as a warm vapor that has low pressure. The compressor uses either pistons or a scroll device to compress the vapor, which increases its temperature and pressure. The refrigerant is then pumped into the condenser coil.

Condenser Coil

Outside air is pumped over the fins of the condenser coil by a fan, allowing the air to carry away excess heat from the refrigerant, cooling it. The refrigerant reverts back to a liquid state, at high temperature and pressure. The refrigerant then enters the expansion valve.

Expansion Valve 

At the expansion valve, the refrigerant is forced through a tiny opening, and is then allowed to expand on the other side, which reduces the pressure and cools the refrigerant. The cool refrigerant then enters the evaporator coil

Evaporator Coil

At the evaporator coil, hot air from inside your home is drawn in by the blower fan and is forced over the outside of the evaporator coil. Small fins allow the coil to absorb heat from the air, warming the refrigerant inside the coil until it turns into a warm vapor. The refrigerant is then pumped back out to the compressor to start the loop again, allowing the heat from inside your home to be transferred outside to the condenser coil. The cooler air that exits the evaporator coil is then distributed throughout your home by the blower fan and a system of air ducts.

To learn more about how an air conditioner works, talk to our HVAC professionals at Lozier Heating and Cooling. We have been serving the greater Des Moines area since 1906. Our goal is to help educate our customers in the greater Des Moines, Iowa area about energy and home comfort issues (specific to HVAC systems). Credit/Copyright Attribution: "GSPhotography/Shutterstock"