Compressor 101: What You Should Know About HVAC/R Compressors

Compressors are a vitally important component of the HVAC/R industry. Compressors, of course, play a key role in effective air conditioning, as well as ductless systems, heat pump systems, and refrigeration equipment. Compressors are used in both residential and commercial HVAC and refrigeration systems, and are necessary in order for equipment to operate.

Therefore, HVAC/R technicians should be armed with the most complete knowledge possible when it comes to compressors. In this article, we’ll talk about hermetic and semi-hermetic compressors, as well as remanufactured versus rebuilt. And, we’ll talk about an important tool that can help you ensure you’ve chosen the appropriate compressor for the job. Keep reading to learn more!

Compressors, defined

If you’re an active HVAC/R technician, you inevitably already know what a compressor is. But if you’ve found this article because you’re a homeowner, or someone looking into a career in the HVAC industry, you might not be entirely aware of the important work that compressors do for air conditioning systems, heat pumps, and refrigeration equipment.

According to Refrigeration School, Inc., compressors play a most important role in the proper functioning of air conditioning and refrigeration equipment. Refrigerant in these types of equipment absorbs heat from an area. This changes the refrigerant from a cold liquid to a low-pressure, warm gas. This gas then enters the compressor, where it squeezes, or compresses, the gas. Its volume is reduced, and it becomes a high-pressure hot gas. The refrigerant in its gaseous form then enters the condenser, there it is cooled by the outside air – once again turning it into its liquid form. Then, the expansion valve lowers the pressure and temperature of the liquid, turning it into a cold gas and sending it back to the evaporator to repeat the heat transfer process.

As you can see, the compressor is a vital chain in this process, and if the chain is broken, the entire system will likely fail. This is why understanding the importance of compressors, how they work, and the different types, is an extremely important part of any HVAC/R technician’s education.

Hermetic Compressors

Hermetic compressors are essentially hermetically sealed units, with the compressor and driving motor both kept in a welded steel shell. A main benefit of a hermetic compressor is that they are protected from contamination from the outside environment, and are virtually leak-proof. They may have a lower operating cost than open compressor types, but can be noisier and vibrate more. The main drawback of a hermetic compressor is that the entire compressor will need to be replaced if it fails, because it cannot be opened to perform repairs. While hermetic compressors often last five years before needing to be replaced, with proper preventive maintenance, this type of compressor may last longer. Because of their relatively short lifespan and their inability to be repaired, they are not used as commonly now as in the past.

Semi-Hermetic Compressors

Like hermetic compressors, the compressor and motor are integrated and are highly leak-proof. But unlike their hermetic counterpart, the semi-hermetic is not encased in a completely welded shell. Instead, it is housed in a metal shell with gasketed covers, so that it can be opened to replace motor and compressor components. This can make the use of a semi-hermetic advantageous, as the entire compressor may not have to be replaced in the instance of failure. This can be preferable, as it is generally less expensive for the consumer to have the compressor repaired as opposed to replaced.

Open Body Compressors

An open body compressor is, quite simply, one that can easily be opened and repaired if need be by an HVAC/R technician. Special gaskets and sealants are used to make sure that the body is leak-free when closed up so the appropriate levels of pressure are maintained.

Different Types of HVAC/R Compressors

Within the three main compressor categories, there are many different types of compressors used in equipment. The most common types and their applications are listed below:

  • Centrifugal: This type of compressor is most often used in commercial air conditioning applications.
  • Reciprocating: This is a very common and typically used compressor, as it can be used in a variety of applications, including appliances, residential, light commercial, and commercial AC, refrigeration, and industrial.
  • Rotary: These compressors are most often used in appliances and in residential air conditioning systems.
  • Screw: Screw compressors are used in mostly commercial applications, including air conditioning, refrigeration, and industrial.
  • Scroll: Like reciprocating compressors, the scroll compressor can be found in a variety of applications, including residential, light commercial, and commercial AC, as well as refrigeration.

Why should I choose a remanufactured compressor over a rebuilt one?

Many times, people use the terms “remanufactured” and “rebuilt” interchangeably. However, in the world of compressors, there are stark differences between remanufactured and rebuilt units. Primarily, a rebuilt compressor is often unauthorized, meaning, not rebuilt by the original product manufacturer. They may not be UL-recognized, and were likely only repaired or rebuilt to old specifications. They may have a very limited warranty coverage, or possibly none at all. It can be difficult to know if the compressor has been rebuilt by a reputable company or individual. As a result, it can cost more in the long run to replace a compressor with a rebuilt.

However, some manufacturers, like Carlyle®, remanufacture compressors in the same facility where they build new units. There are multiple benefits to choosing a Carlyle remanufactured compressor, some of which include:

  • Carlyle factory-remanufactured compressors are UL-recognized.
  • These compressors are completely remanufactured to current OEM specifications right at the Carlyle facility, using genuine parts.
  • All critical wearing components, rings, valves and bearings are replaced – even if they don’t need to be.
  • Cylinder walls are re-honed and the crankshaft is re-machined and polished to ensure reliable performance.
  • Bores are measured with a highly sensitive air gauge.
  • Authorized remanufacturers and Carlyle personnel audit quality control measures.
  • All compressors are 100-percent run tested, under load.
  • Carlyle remanufactured compressors are backed by Carrier® Corporation service and warranty programs.

How do I know what the right compressor for my application is?

Obviously, whenever you need to repair or replace the compressor in any equipment, you should refer to the manufacturer manual first and foremost to ensure you’re choosing the right compressor for the application. When you choose your local Carrier/Bryant® Distribution Center to help you find the parts you need, you’ll have the added benefit of our extensive cross-reference database tool. With tools to help you find both hermetic and semi-hermetic compressors that will be compatible with your application, locating the appropriate compressor for the job is simplified for you.

Where can I find the compressors I need to complete any HVAC/R job?

You can find the replacement compressors you need at your local Carrier/Bryant Distribution Center. There, you’ll find a complete lineup of quality compressors, including brands like Carlyle, Copeland®, Goldstar®, and many, many more. No matter what OEM equipment you’re using we have the HVAC compressor you're looking for. Simply provide us with the manufacturer’s part number, or information like capacity, voltage, phase, refrigerant and type (reciprocating, scroll or rotary), and we will be able to easily find the replacement compressor you need. Plus, we have all the compressor system components you need to get the job done. You can find your local Carrier/Bryant Distribution Center by using our convenient distributor locator.

Igor Bychkov, Product Manager