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On a hot summer day, you may turn on the air conditioner to cool your home and be curious as to how it works. This article will look at what an air conditioner compressor is and what it does. Next time you go to flip on the thermostat, you’ll understand precisely how it works.

Depending on your home, you may have a split system which you would find an outside unit containing the condenser and the compressor and the evaporator would be on or inside the air handling unit such a forced-air furnace.  Or you may have a package system which includes all the components within a single outdoor unit that can is found either on the ground or your roof.

No matter what type of system you have, they both contain the main parts which keep your home cool during the summer months.  The compressor can be comparable to a heart within a human body; but in this case, drawing in cold low-pressurized air from inside of the house.  The compressor will squeeze or compress the refrigerant which raises its temperature, and then exits the compressor as the high-pressure gas.

There are several components of a central air conditioning system that work effortlessly to cool down your house.  But with every well-working machine, it’s important that regular maintenance is scheduled for it to work as it should.  You can ensure that your compressor will last its full life expectancy by making sure that you schedule it at the beginning of the spring season.


Within your outdoor AC system is the compressor along with a condenser, expansion valve and evaporator.  It takes the warm air and pumps it through the refrigerant which then carries colder air into your home. The refrigerant itself is a fluid that absorbs heat, but after awhile it may wear out or leak causing the warm air to blow into the house.  

A refrigerant is the same thing used in your kitchen’s refrigerator to keep the food cold, in the same way, to keep your home at your desired temperature. A well-trained but certified technician can quickly fix the refrigerant that is low or in need of a recharge.


When it comes down to how precisely a central air conditioning compressor works, the refrigeration cycle itself happens in several steps:

The compressor pumps the outside air into the refrigerant from the outdoor unit into the indoor unit’s evaporator.  At this stage, the refrigerant absorbs the heat and which turns it into colder air. Next, the liquid converts into a vapor.  Holding only as much heat as it can, the vapor of the refrigerant travels back into the compressor which is also bringing the heat away from your home.

When the heated refrigerant that is now vapor travels back to the outdoor air conditioning unit, the compressor begins to pull in the refrigerant and reheats it to a gas.  That gaseous refrigerant then dumps the heat into the colder outdoor air. As it loses heat, the refrigerant begins to turn back into a liquid.

Finally, once the refrigerant has lost a significant amount of the heat, the compressor sends it to the indoor air conditioning unit until the temperature inside matches the temperature on the thermostat.


Most manufacturers offer two types of compressors:

  • A reciprocating compressor
  • A scroll-type compressor

A motor powers the reciprocating compressor, and just like a motor in a car, it contains a cylinder and piston.  The external power is what compresses the refrigerant inside of the cylinder. From this type of compressor, there are three different types, hermetically sealed, semi-hermetically sealed as well as an opened type.

A scroll compressor consists of two interleaved scrolls where one is a fixed scroll while the other orbits eccentrically without being able to rotate.  During this process, it produces small gaps between the scrolls where the refrigerant is compressed. Shapes of the scrolls include involute, an Archimedean spiral or a hybrid curve.  When it boils down to it, all scroll compressors must rotate eccentrically to produce the compression of the refrigerant.

Scroll-type compressors within the air conditioning unit tend to cost more but prove to perform more efficiently than the reciprocating compressors.  Since manufactures offer their air conditioning units with both, it may be worth researching to see which one would be best for your home.


There are several types of refrigerant used in today’s air conditioning systems.  Having the right kind of refrigerant is essential depending on the system as well as the amount of your air conditioning system.  It is important to note that too much or too little refrigerant is both harmful to the compressor.

R-22 Refrigerant was used up until 2010 and discontinued in use in 2015.  It was often referred to by the brand name of Freon®. It contained a hydrochlorofluorocarbon or HCFC that was found to contribute to the depletion of the ozone layer.  

R-410A Refrigerant known by its brand names Puron®, Suva® 9100, or Genertron AZ-20®, approved for use in newer air conditioning systems.  This type of refrigerant is used for commercial unitary air conditioning systems.

R-407C Refrigerant is also referred to by Suva ® 407C or Genetron® 407C.  This type closely matches the characteristics of R-22 refrigerant but does not contribute to the depletion of the ozone layer.  It can be used in place of R-22 and has proven to be the similar conversions in the way of operating pressures.

The EPA recognizes that R-410A contains no chlorine making it environmentally safe for the ozone.  You will find that most well-known brands are using this alternative in many of the air conditioners installed today.


Compressors are a crucial component of the air conditioning system.  If it fails, it can mean trouble for the rest of your system. You’ll have to make sure that this outdoor unit is free of any obstructions on the sides and the top for it to work efficiently to pull in and push out the air it uses for bringing down the temperature.  

Compressors themselves are pricy to fix if they fail before you need a new unit.  Unless they fail within the first year of installation, you may have to pay on average $645 for supplies to fix it if it is still under warranty.  Outside of the warranty, you are looking at double that price, on average $1,200 for labor, supplies, and cost of the parts.

If you learn better by viewing what you read here, check out this short video by How Stuff Works for a simple explanation how the compressor produces colder air for inside your home.

If you feel your compressor in your air conditioning unit is not working as it should, it is time to reach out to a local professional. From there, the expert can help determine the problem, also ensuring that routine maintenance is done regularly on your air conditioning unit so the compressor will last for its expected 10 to 15 years.

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