Central Air Conditioner: How The Box Outside Produces Cool Air Inside

Posted on: 24 June 2015


If you have a central air conditioner, you probably just take it for granted that it produces cool air. However, if you are the particularly curious type, you may want to know how that large box located outside your house produces the cold air inside your house. Knowing how your air conditioner works is not just a fun pursuit, but it also helps you determine what could be wrong with your air conditioner when it does not seem to be working correctly.

The "Box" Surrounding the Unit

The "box" outside may be square, rectangular or even cylindrical. The professionals refer to this part as the condenser. The hull of the condenser serves three purposes:

  • To protect all the parts inside
  • To disperse hot air and moisture taken from inside of the house through the unit's fan
  • To filter the outside air through the slats in the box. There is an air filter right behind these slats that prevents dirt and debris from entering the system.

If the box is damaged, then you should have an HVAC contractor examine the rest of the air conditioner just to make sure that everything inside the box is still functioning and safe from harm. You will still have to replace this outer shell because it is vital to the safety and function of the rest of the unit's parts.

Inside the Condenser

If you were to remove the outer hull of the condenser, along with the filter, you would see the following components inside:

  • The refrigerant cylinder
  • Electrical wires which keep the unit running and activate the compressor
  • Copper pipe, which connects all of the components together

When you hear strange sounds coming from within the condenser box, it usually means that something is amiss with the compressor, or that there is a blockage in the copper pipe that connects all of the components.  There may be issues with the refrigerant and/or its cylindrical container as well.

Inside Your House

All of the outside components are linked to the evaporator coil and the expansion valve, which are next to your furnace. The expansion valve releases just the right amount of refrigerant, pulled from the outside, and passes it over the evaporator coil, cooling the warm air that has been pulled from your home. If your home is not cool enough, but everything appears to be and sounds like it is running correctly outside, then the trouble is with your expansion valve or the evaporator coil. The copper pipe circles back out to the condenser, where excess refrigerant is returned to the source, and the cycle begins again.