What Are the Different Types of HVAC Compressors?
HVAC, or heating, ventilation, and air conditioning, refers to the different systems and components used to circulate air and regulate its quality. The compressor is one of the most important components of an HVAC system. Still, there are several different types of compressors, which can make the system even more confusing.
There are five types of HVAC compressors used in both commercial and residential settings. They each serve the same general purpose but operate differently, and there are pros and cons to each. These HVAC compressor types include:
- Reciprocating
- Scroll
- Screw
- Rotary
- Centrifugal
HVAC Compressor Types
HVAC systems involve heating and air conditioning, as well as ventilation and refrigeration. Air conditioning compressors are the heart of the air conditioning system. They work by compressing refrigerant to increase the temperature. Then, the refrigerant gas enters the condenser allowing air to be cooled.
There are five types of air conditioning compressors: the reciprocating compressor, scroll compressor, screw compressor, rotary compressor, and centrifugal compressor.
HVAC Compressor Cost Estimates
| Min. Price Estimate | Max. Price Estimate | |
| Reciprocating | $400 | $7,000 |
| Scroll | $500 | $2,000+ |
| Screw | $350 | $20,000+ |
| Rotary | $900 | $8,000+ |
| Centrifugal | $10,000 | $25,000+ |
Let’s take a closer look at each of these compressor types in more detail.
Reciprocating AC Compressor
The reciprocating compressor is the most common type and it’s also sometimes referred to as a piston compressor. These versatile compressors work by using an internal piston to push the air up and down inside a cylinder.
When the piston, which is powered by a motor and crankshaft, moves up and down inside the sealed space, it creates a vacuum suction effect which pulls the refrigerant gas into the system. When the piston moves in the other direction, the refrigerant gas is compressed, pushing it into the condenser.
These types of compressors are efficient and versatile because you can get larger ones with more pistons if needed. Some compressors have up to 8 cylinders and pistons, but others may only have 2 or 4.
Scroll AC Compressor
Scroll compressors are more efficient and reliable than the standard reciprocating type, so they’re becoming more common within HVAC systems. They’re also sometimes referred to as scroll pumps or scroll vacuum pumps.
Unlike the up-and-down piston motion, scroll compressors use circular motion. They have fewer moving parts than the reciprocating compressors, and require less torque variation.
Because of their design, scroll compressors are often quieter and have more reliable operations than reciprocating compressors. They’re efficient and affordable, so they’re frequently found in new homes.
Scroll compressors may be single stage, two-stage, or variable capacity. Single stage compressors are what are most commonly found in residential systems, because they’re less expensive and can heat or cool most homes effectively.
Two-stage compressors can adjust themselves based on the system’s needs. These are also used in some residential HVAC systems. They can run more efficiently at lower speeds to help remove humidity from the air or run at full capacity if needed to maintain the desired temperature.
Two-stage systems are normally more energy efficient than single stage systems because they can adjust to the home’s needs, but they may be more expensive up front.
The most advanced compressor is the variable capacity, which is the most energy efficient and can adjust itself to optimize performance. These are normally the most expensive of the scroll compressors.
Screw AC Compressor
Screw compressors are commonly found in large buildings that take a lot of air movement to keep the space cooled to the desired temperature. These compressors are reliable and work efficiently to cool large, commercial spaces.
Inside the unit are two mated helical rotors (or screws). Screw compressors are classified based on how many rotors or screws are inside the unit. They may be either single or twin-screw compressors.
Single-Screw Compressors have two gate rotors along with the main rotor, which is the driving rotor. The main driving rotor is what moves the other rotors to operate the compressor.
Twin-Screw Compressors have two helical grooved rotors which mesh with one another to allow the refrigerant to flow. Twin-screw compressors are typically used in larger systems, like those in commercial or industrial settings.
Compared to the other compressor types, screw compressors are simple and easy to maintain. They are powerful and have a higher output than some of the others, and they don’t produce too much sound.
So, they’re a good choice when noise is a concern but you need to cool a large space.
Rotary AC Compressor
Rotary air compressors are smaller than some of the other types, making them ideal for spaces where you need a small footprint. These compact units are efficient and reliable, and they’re used across a variety of applications.
Rotary compressors have a simple design with fewer moving parts making them less likely to malfunction and easy to maintain.
They operate by rotating a roller inside the cylinder to compress refrigerant gas, just like reciprocating and scroll compressors. The rotary compressor is best suited for use with an inverter-type system for maximum efficiency.
Rotary compressors are normally used in smaller systems like split residential units. They’re good for noise reduction and operate efficiently with minimum vibrations.
Centrifugal AC Compressor
Centrifugal compressors, also sometimes called turbo compressors or radial compressors, are only used in very large HVAC systems.
They’re the largest, most complex, and most expensive of the various HVAC compressor types we’ve discussed. Still, the design has been around for decades, with the earliest compressors appearing in the early 1900s.
These compressors use centrifugal force to move the refrigerant through the system, compressing the refrigerant gas using an impeller. They’re commonly used in chilled water applications, almost exclusively in industrial or commercial settings.
Unlike the other types of compressors, centrifugal compressors don’t use pistons, valves, or cylinders to build pressure. So, there are fewer moving parts that need attention or malfunction.
Because of the design, centrifugal compressors are very reliable and operate efficiently, especially when running at higher speeds.
How to Choose an HVAC Compressor
Choosing the right HVAC compressor for your home or other building comes down to understanding your heating and cooling needs. Some types are only suited for very large systems and would not be cost or energy efficient for smaller, residential systems.
On the other hand, small systems would not be effective to heat and cool very large spaces.
Let’s take a look at how the different compressor types compare with one another to help you better approach the decision for your space.
HVAC Compressor Comparison
| Reciprocating | Rotary | Scroll | Screw | Centrifugal | |
| Cost per KW | Low | Average | Average | High | High |
| Efficiency | Low | Average | High | Very High | Very High |
| Sound/Vibration | High | Average | Average | Very Low | Very Low |
| Input Power | Average | Low | Low | High | High |
| Lubrication | Oil | Oil | Oilless | Oil | Oilless |
Which HVAC Compressor is Best for a Home?
For residential systems, rotary or scroll compressors are normally the best option. They’re more energy efficient and advanced than the reciprocating type. Still, the cost for HVAC compressors can vary quite a bit depending on size and model, so you’ll also need to consider your budget.
Remember, more efficient units and those with better warranties or a longer lifespan typically come with a larger price tag, too. So, it’s important to consider the full lifetime cost of the unit in addition to the up-front investment.
The Bottom Line
An HVAC system is a huge investment in any home or business, and the compressor is the heart of that system. The type of HVAC compressor best suited for your system will depend heavily on the building’s size and use. The environmental conditions will also have an affect, since they’ll impact how hard the system has to work.
Still, understanding the different types of compressors available and how they work will help you to better make a decision for your HVAC system. You’ll also be able to understand how they’re similar and some of the pros and cons of each.
Energy efficiency and capabilities are important considerations for any system. You’ll need to find the right balance of the two and find a compressor within your budget that will get the job done.
Technology in the HVAC field is changing and improving all the time, but you’ll have to pay a premium to get the newest and best equipment. However, it may be worth it if the unit saves you money and headaches in the long run.
Then, be sure to keep up with any necessary and preventative maintenance so your compressor and HVAC system will be in tip-top shape for years to come.
