The Basics of Air Conditioning – How Your Air Conditioner Works

How Your Air Conditioner Works

An air conditioning system is one of the most complex devices found in a home. In fact, it pulls off some pretty fancy science day in and day out without a hitch. But not to worry! This article will keep it simple. And we promise—no math or physics.

Who Should Read This

Are you deciding to buy or repair an air conditioner? If so, Knowing about the parts of the system will help you:

  1. Know what’s not working
  2. Estimate how much repairs might be
  3. Know if it’s time to replace all or part of your system

For Ace Pro Heating and Air, an informed customer is our best customer. You’ll be surprised&emdash;it’s easy to understand what your repairman is saying!

How Air Conditioning Systems Work


A typical air conditioning system has three main parts. It has an air handling loop, a cooling loop, and a control system. The air handling loop circulates indoor air to cool it. The cooling loop circulates refrigerant that removes the heat from the indoor air and carries it outdoors. The thermostat controls when the air conditioner comes on and shuts off to keep it comfortable inside the house.

Special terms are shown in small capital letters.

The two parts of an air conditioner we’re most concerned with are the air handling loop and the cooling loop. First, an air conditioner removes hot indoor air from the house. It then transfers the heat to the outdoors and blows the cooled air back into the house. Lowering the temperature of the air also makes it less humid. Figure 1 is a picture of the steps.

Diagram of how heat is transfered in an air conditioning system

Figure 1

  1. 1. The air handling loop pulls hot air from inside the house.
  2. 2. The hot air passes through the cooling loop. The heat transfers to the cold fluid in the cooling loop, cooling the air.
  3. 3. The cooling loop carries the heat out of the house.
  4. 4. The air handling loop blows the cool air back into the living space.

The Air Handling Loop

The air handling loop circulates the indoor air. A blower in the air handler pulls the hot indoor air into the return. The indoor air then moves through the ducts to the evaporator.

The evaporator is a special part of the system. It belongs to both the air handling loop and the cooling loop. The evaporator has metal coils with a cold fluid inside of them. Figure 2 shows how it works:

Diagram of a typlical Air Handling Loop

Figure 2

  1. 1. Warm indoor air is pulled into the return.
  2. 2. It travels through the ductwork into the evaporator.
  3. 3. The the evaporator removes the heat from the warm air.
  4. 4. The indoor air, now cool, is drawn into the air handling unit.
  5. 5. The air handling unit blows the cooled air through the ductwork.
  6. 6. The cooled air is blown back into the living space through the vents.

This is how air conditioning keeps our homes cool even on the hottest summer day.

The Cooling Loop

The second major part of an air conditioner is the cooling loop. Refrigeration makes things cold by taking heat out of them. The cooling loop is like a refrigerator for your house. It makes the inside cool by carrying the heat outside.

The first piece of the cooling loop was already discussed. It is the evaporator. The evaporator has a set of metal coils filled with a cold fluid. This important fluid is the refrigerant. Refrigerant takes the heat from the air handling loop and transfers it to the cooling loop. Let’s look at this in more detail.

The refrigerant absorbs the heat from the indoor air at the evaporator. The heat from the indoor air is then carried to the condenser unit. The condenser unit is usually located outside the house on a concrete slab. It is a large machine with a fan. It usually looks like the machine shown in Figure 3.

Diagram of how heat is transfered in a typical condenser unit.

Figure 3

  1. 1. The refrigerant carries heat from the indoor air to the condenser unit.
  2. 2. Inside the condenser unit is the compressor. The compressor is a pump that raises the pressure of the refrigerant. This causes the refrigerant to heat up.
  3. 3. The heated refrigerant is then passed through the condenser. The condenser acts like the radiator on your car.
  4. 4. Outside air is pulled through the condenser coils by the condenser fan.
  5. 5. The heat is pulled out of the refrigerant by the outside air.
  6. 6. The hot air is blown out of the condenser unit.
  7. 7. The refrigerant leaves the condenser coils.
  8. 8. The cold refrigerant now heads back to the evaporator to repeat the cycle.

The Control System

All we need now is a way to turn the air conditioner on and off. This is usually done with a single thermostat. The thermostat reads the temperature inside the house. If the indoor air is too hot, it turns the air conditioner on. Once the inside air is cool enough, the thermostat turns the air conditioner off.

In Conclusion

There you have it. Pretty simple, huh? Warm indoor air is pulled out of the house and through the ducts. The heat is removed in the evaporator. From the evaporator, the heat gets passed outside and transferred into the outdoor air. The cool air is blown out of the vents and into the house.








Comments are closed.