What Does an HVAC Compressor Do?

Written By Lester Mclaughlin
Updated On

Are you wondering what an HVAC compressor does?

You’ve come to the right place!

In this Blue National HVAC guide, you’ll learn:

  • What compressors do in cooling systems
  • How compressors work
  • What to do if your compressor fails

And much more!

What Does An HVAC Compressor Do

So, if you’re looking for information about air conditioning compressors, keep reading our detailed guide below to get answers to all of your questions!

What Does An Air Conditioner Compressor Do? 

The compressor is the heart of the air conditioner. The short answer is that compressors are responsible for moving refrigerant throughout the entire air conditioning system, which is the core process that removes heat from your home. 

With that in mind, let’s dive into the basics of how an air conditioner works so you can get a better understanding of the crucial role the compressor plays in the process.

A central air conditioning unit and air-source heat pump are considered “split” systems, and this means they have an indoor unit and an outdoor unit connected with refrigerant lines that refrigerant flows through. 

Think of this split system as a circle, or closed-loop, with two refrigerant lines connecting the indoor unit (air handler) to the outdoor unit (condenser). 

Many people think refrigerant and freon are the same thing, however freon isn’t used in AC systems anymore due to EPA regulations.

The refrigerant travels between the indoor and outdoor unit, gathering heat from the indoor of the home and taking the heat to the condenser unit where it dumps outdoors. The refrigerant experiences high-temperature and low-temperature states as it travels through the closed-loop system.

The indoor unit contains evaporator coils, which cold refrigerant flows through. Warm indoor air blows across the evaporator coils, and the refrigerant absorbs the heat from the warm air, cooling it. 

The cool air is then blown to various rooms in the house via the ductwork while the now hot refrigerant travels along the refrigerant lines back to the outdoor unit.

The outdoor unit contains condenser coils and a large fan that cools the refrigerant with outdoor air. This heat transfer process repeats until the inside temperature reaches the thermostat’s setpoint. 

The essential component of this whole process is the compressor. It keeps the refrigerant flowing throughout the closed loops. Think of it as a pump that can also compress liquids and gases to higher pressures. 

Where is the Compressor Located?

The AC compressor sits inside the outdoor unit (also called the condenser). Typically, you can’t see the compressor itself during regular operation as the fan cover, and the coil “walls” surrounding it blocks the view. 

However, if you disconnect power to the outdoor unit and remove the screws of the top lid/fan chassis, you can take a look at the compressor. Just be careful with the wiring harness that connects the fan to the condenser. 

How Does the Compressor Work? 

The compressor inside your air conditioner works by pulling in low-pressure gaseous refrigerant with a spinning rotor. The rotor sits inside the round housing of the compressor and is off-center, meaning the hub of the rotor is closer to the outlet than the inlet. It outputs liquid refrigerant under high pressure.

The rotor is closer to the outlet, and the pressure on this side is higher since the refrigerant gas moves from a larger area to a smaller area.

The core principle of the compressor is it forces liquids and gases through a smaller area to increase its pressure (or compress it). This high-pressure change also increases the temperature of the refrigerated gas due to the ideal gas law. This law makes the reverse also true, when the gas expands at the expansion valve, it rapidly cools. 

Do You Need Compressor Maintenance?

All HVAC compressors require routine maintenance to ensure they are functioning optimally. Like the rest of your HVAC system, compressors have myriad moving parts that are subject to wear and tear over time. 

Having your compressor serviced regularly provides the best efficiency and ensures the longest equipment lifespan possible. 

What Are The Most Common Compressor Failures? 

Even with proper service and maintenance, compressors can still have issues that necessitate a repair. For that reason, if you ever notice anything out of the blue or strange with your AC unit, call our HVAC service technicians right away.

Ignoring a potential warning sign of a compressor failure can quickly grow from a minor issue and easy repair to an expensive failure.

Here is what all homeowners should look out for on their compressor and air conditioning system: 

Lack of Cooling

If your AC unit is having trouble cooling your home or is blowing hot air, it could be due to issues with the compressor.

High Humidity

When the air cools from evaporator coils in the AC unit, humidity also condenses out of it. This could be from the compressor not pumping enough refrigerant.

Abnormal Noises

Sudden changes to the sounds your outdoor unit makes can be an indicator the compressor is in trouble. Normal sounds are a medium to loud humming sound, while problem sounds include rattling, buzzing, hissing, bulbing, and screeching.

Hard Starting 

Hard starting is usually from an electrical or mechanical problem with the compressor and can be identified by the compressor having issues to turn on – it will try to start then immediately stop repeatedly.

Blocked or Dirty Condenser 

A blocked condenser reduces airflow across the condensing coils and prevents proper heat exchange with the outdoors. While it is not an issue with the compressor itself, it can lead to compressor failures.

What Should You Do if Your Compressor Fails?

If the compressor of your HVAC system fails, there is not much you can do unless you have extensive HVAC experience. 

You can do some basic troubleshooting yourself, but if your AC unit isn’t cooling, you’ll have to contact an HVAC professional. 

To get your issues diagnosed and repaired, give our team of expert HVAC technicians a call today. They will get you back up and running in no time at all. 

HVAC Compressor Repair 

When air conditioners are running, the compressor is performing the brunt of the work. As such, compressors undergo an increasing amount of stress as outside air temperatures rise. 

Common failures include dirt and dust contamination, broken seals, worn bearings, refrigerant leaks, and electrical failures. However, they often have great lifespans and most manufacturers have lengthy warranty terms for their compressors. 

However, whatever the issues are, our HVAC technicians have the necessary skills to repair or replace the compressor – so call us today if you need assistance. 

Meet Your HVAC Expert

Lester Mclaughlin

HVAC systems are highly technical and often is the most misunderstood part of the house. From ductwork to heat pumps, I've been exposed to all sorts of issues facing homeowners. It really irks me when a homeowner is given bad advice like refilling freon vs fixing a leak in the system. I'm here to help our website readers with their heating and a/c problems.
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