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The Job of Your AC’s Compressor

Kilowatt AC Service technician with rooftop compressor

If you’ve read other of our blog entries or articles about air conditioning systems, you may have seen compressors called the “heart” of air conditioners. You may also know that when a compressor dies, it often spells the end of the whole air conditioner. (Whether you need to replace the compressor, the whole condenser, or the entire AC system depends on several factors we addressed earlier this year.)

Aside from these points about a compressor, many people don’t know what it is the compressor does that allows for an air conditioner to work. We’ll put the compressor under a microscope in this post to help you understand more about how your air conditioning in Van Nuys, CA works from day-to-day.

The Compressor Basics

What does a compressor do? There’s a hint in the name: it compresses the refrigerant inside it. This is necessary for the AC to carry out heat exchange, which is the process it uses to cool a house.

Here’s a simple sketch of heat exchange and the compressor’s central role in it:

  • Cold refrigerant moves through an indoor coil, known as the evaporator coil, where it draws heat from the indoor air. The refrigerant changes from a cold liquid to a warm, low-pressure gas—in other words, it evaporates.
  • This warm low-pressure refrigerant gas enters the compressor in the outdoor condenser cabinet. The compressor puts pressure on the gas (compresses it), which turns it from a warm, low-pressure gas to a hot, high-pressure gas.
  • This hot gas passes through the outdoor condenser coil. As outdoor air flows over the coil, it removes the heat from the gas, turning it into a high-pressure, cool liquid.
  • Before the refrigerant enters the indoor evaporator coil to restart the cycle, it moves through an expansion valve to lower the pressure of the liquid—and this turns the liquid cold.

How the Compressor Works

Going deeper into the details, let’s examine how the compressor does its … compressing. There are different types of compressors, such as reciprocating, rotary, scroll, and screw compressors. For the sake of simplicity, we’re going to look at the most common, the reciprocating compressor.

The compressor resembles a combustion engine. A crankshaft drives a row of pistons inside cylinders. The low-pressure refrigerant gas enters the pistons through a suction line, and the crankshaft drives the pistons to squeeze the refrigerant. When the refrigerant pressure is high enough, it exits through a discharge valve. The suction line and the discharge valve open and close in succession as the crankshaft moves the pistons up and down, with the pressure of the gas forcing open the discharge valve.

You might think, “Hey, that’s pretty simple!” But working on a compressor is anything but simple. The powerful motor action necessary to drive the pistons in the compressor requires specialized technicians to inspect them and help head off possible breakdowns. Just like an engine breakdown in a car, a broken compressor will bring the system to a complete halt.

If you think your compressor is heading for trouble because of hard-starting or strange noises from the condenser cabinet, call our experts right away!

Call our friendly technicians at Kilowatt Heating, Air Conditioning and Electrical 24/7 for exceptional customer service! We’ve served Los Angeles, Van Nuys, and the San Fernando Valley since 1990.

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