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Commercial refrigeration compressors: what are they and how do you choose the right one?

Commercial refrigeration compressors

The compressor is a vital part of your refrigeration system. But what exactly is it? What does it do? And how do you know which type is best for your equipment and system?

Here, we’ll explore all you need to know about industrial and commercial refrigeration compressors.

What is a refrigeration compressor?

A refrigeration compressor is an integral part of refrigeration equipment – industrial and commercial alike.

Its role is to transport the refrigerant – also known as the working fluid – through the refrigerant circuit. It does this by compressing the refrigerant coming in from the suction side and pushing it to high pressure and temperature.

The pressure and temperature changes that the refrigerant experiences cause it to absorb heat, boil and turn into gas – before releasing this heat and condescending back into a fluid.

This process is fittingly known as the vapour compression cycle.

Without the compressor, this journey wouldn’t take place, the refrigerant wouldn’t change state, and your refrigeration system wouldn’t be able to do its job of cooling. So, the compressor really is at the heart of the whole refrigeration process.


What are the different types of commercial refrigeration compressors?

There are two main types of refrigeration compressors: dynamic and positive displacement.

The difference lies in how they compress the refrigerant.

Dynamic compressors compress a refrigerant by increasing its speed, using a high-speed rotor. They then convert speed to pressure in the diffuser.

Meanwhile, positive displacement compressors compress the refrigerant by collecting it in a chamber and then reducing the chamber’s volume.

Positive displacement compressors are complex devices, but they’re much more straightforward from a control automation standpoint.

Dynamic compressors can stall, which can lead to a surge. Essentially, when the compressor stalls, it no longer has any force to resist the pressure increase it’s created so the gas starts to move to the area of lower pressure.

On the other hand, a positive displacement compressor isn’t prone to stall and can’t surge, so it requires much less attention.

Having said that, there are several different types of compressors that fall into the positive displacement category. These also fall into two main groups.

Reciprocating compressors

Also known as piston compressors, these use the reciprocating motion of a piston to compress the refrigerant inside the cylinder. The piston is moved using a crankshaft with an electric motor.

These compressors:

  • Have a more constant flow thanks to inlet and exhaust valves
  • Use silent-block to counter the high vibrations
  • Have a connection for oil balancing
  • Can be mounted on an individual, tandem, trio or tack basis

Reciprocating compressors come in three key types.

1. Hermetic

Hermetic compressors are used in small commercial applications.

You can easily identify them as they have a single case that’s completely sealed and contains both the compressor and drive motor. This prevents any potential refrigerant leaks from occurring.

That said, they have a couple of downsides. Firstly, refrigerants like ammonia can’t be used as they can damage the materials it’s made of. And secondly, these compressors can’t be repaired after a breakdown.

2. Semi-hermetic

Semi-hermetic compressors are mainly used in commercial settings.

They’re made up of two separate housings, which means this time you can access the compressor to maintain and repair it.

However, the motor and the refrigerant do come into contact, so not all refrigerants can be used with this kind of compressor. Plus, there’s a higher chance of refrigerant leaks occurring.

3. Open

Here, the motor and compressor are divided into two independent modules, linked by a mechanical transmission.

This means the compressor can be easily accessed for repair and maintenance, and the construction prevents vapours from overheating before they enter the cylinder. Better still, these compressors can accommodate any refrigerant fluid.

That said, they do come with a higher risk of refrigerant leaks.

Rotary compressors

This group of positive displacement compressors don’t have suction valves, which makes for a continuous compression flow.

These compressors also rely heavily on oil for lubricating and sealing.

There are several different types of rotary compressors – you can tell them apart by their differing motor movement. Here are three of the most common.


Here, the movement of the motor shaft is driven by the refrigerant fluid itself, which fills the space between the compressor rotor and stator.

As the space decreases at the point of minimum diameter inside the compressor, the refrigerant gets compressed.

These compressors have a spring-loaded vane in a slot in the cylinder, hence why they’re also known as vane compressors. This spring divides the compressors’ suction phase and discharge chamber.


Scroll compressor types are centred around the orbital movement of a spiral.

These compressors are constructed from two like-for-like spirals, known as the stator and the rotor. The stator, which is top and fixed, has an exhaust port at its centre. Meanwhile, the lower spiral, known as the rotor, orbits inside the stator.

As it does so, the movement of the fluid pockets within the walls causes it to move inwards, which then increases its pressure.


Screw type compressors are used in industrial applications for medium and high power ranges.

They’re formed of two conjugated rotors – one ‘male’ and one ‘female.’ The male rotor is coupled to the electric motor and forms lobes while the female rotor has alveoli. Meanwhile, a part called a slide opens and closes the access of the refrigerant to the rotors to vary the power.

These compressors have an oil separator and oil injection control, as they rely on a direct injection of oil at a controlled temperature to lubricate them. This oil also provides sealing and absorbs the heat of compression.

Refrigeration compressor

Choosing a commercial refrigeration compressor

Screw compressors are currently the most widely used type of compressor in industrial refrigeration – although reciprocating processors were the most popular not so long ago.

It’s your system designer’s job to determine the best compressor for your needs. But here are some factors to consider all the same.

1. Cooling capacity

A single screw can provide more cooling capacity than a reciprocating compressor. This is one of the reasons why screw compressors are proving most popular in industrial settings today.

However, it’s important to assess the cooling capacity of your system with your operating conditions in mind.

This includes:

  • Minimum condensing temperature (which affects the lubrication of your compressor)
  • Maximum condensing temperature (which affects the maximum compressor pressure)
  • Maximum evaporation temperature (which affects high mass flow rate, connecting rods and excessive force on bearings)
  • Low evaporating temperature (which affects low gas density and insufficient cooling of the engine)

2. Cost

Screw compressors cost more than reciprocating compressors.

However, only one screw compressor is usually needed, whereas above certain capacities, you may need several alternatives. This can make a screw compressor the lower-cost option overall.

On top of this, screw compressors typically come with low maintenance costs.

3. Energy efficiency

Reciprocating compressors are more efficient than screw compressors, both at full and part load.

This makes them a viable alternative to the more widely used screw compressor in industrial refrigeration.

Higher energy efficiency can lead to lower energy bills and reduce your impact on the environment.

4. Noise

Screw compressors tend to vibrate less than reciprocating compressors, as they’re not unbalanced in the same way. This can make them less noisy.

However, reciprocating compressors use silent-block to counter the high vibrations.

These are just factors to bear in mind – your system designer will be able to design a system for you that meets any necessary noise restrictions.

5. Size

Some compressors are more compact than others. So, if space is at a premium in your business premises, size could be a deciding factor.

For instance, hermetic compressors have just one case containing both the compressor and drive motor, and are usually used in small commercial applications.

6. Refrigerant choice

As we’ve touched upon already, not all refrigeration compressors can be used with every refrigerant.

Refrigerants largely fall into two groups: natural and synthetic.

Synthetic refrigerants, by which we’re largely referring to HFCs and HFOs, tend to be harmful F-gases, with a global warming potential (GWP) of several thousand. They also release dangerous ‘forever chemicals’ called PFAS into the environment, which poison wildlife and, in some areas, also endanger human health.

On the other hand, natural refrigerants are low-GWP, clean and non-toxic. They’re also high-performing and have become widely adopted by the refrigeration industry.

Choosing a compressor that can be used with natural refrigerants like propane and CO2 is the best way to lower your business’ carbon footprint. It will also protect your business from regulatory updates that could risk your refrigeration system becoming a stranded asset in the future.

Let us worry about refrigeration compressors for you

At Clade, we can design, manufacture, install and maintain your commercial refrigeration system for you so that you don’t have to worry.

Our system designers will take the time to understand your business’ needs, and will pick out the best compressor for you as part of a larger system design tailored to your requirements.

As a certified B Corp, we only work with natural refrigerants. So, when you work with us, you know you’re having a positive impact on both people and the planet.

Get in touch with us here at Clade to learn more about how we can help you with your refrigeration needs.