There are so many types and models of air compressors available, it’s easy to get confused. And besides the many models and sizes, there are extra options like dryers and filters.
Don’t worry. Once you know what to look for, buying the right air compressor is fairly simple and straight forward process.
To make the right decision, we must know:
- The best type of air compressorfor our application.
- The required
- The required capacity (flow rate) of the air compressor.
- Extras and options..
There are basically two types of air compressors that are of interest here: the rotary screw air compressor and the reciprocating piston air compressor. it is very important to choose the correct type for your situation. I will give you some basic rules of thumb so you can be confident to buy the right type.
Then there is the pressure and the capacity of the compressor. This is all about size and power.
A too small air compressor won’t get the job done, but a too big compressor can be even worse (think of: wasted money on a too expensive compressor, higher maintenance costs, higher energy costs).
Last, we need to make the decision whether we need extras like compressed air dryers, filters and stuff like that.
I will cover these points one by one.
But first, let’s talk about the basics: air pressure and compressor capacity.
What type of air compressor do I need?
The two most popular air compressor types are the:
- Reciprocating (piston) air compressor
- Rotary screw air compressor
Other types include scroll, turbo, rotary vane compressors, but those are mostly used for specific applications. You can forget about those for now, let’s focus on the two main types of air compressors: the reciprocating compressor and the rotary screw compressor.
The reciprocating compressor
The reciprocating compressor compresses air with the use of one or more cylinders/pistons. The pistons move up and down (=reciprocating) inside the cylinders to compress the air. Reciprocating compressors:
- Can be low to very high pressure (7 – 1000 bar or 100 – 15.000 psi)
- Are low capacity
- Are designed for intermittent use
Reciprocating compressors are relatively small compressors. They go up to about 10 HP (or 7 kW). They are often be found at, or used for:
- Do-It-Yourself /at home
- Small businesses
- Construction work (nailers etc)
I will cover the difference and benefits of single stage vs two stage and duplex air compressors in the reciprocating air compressor buying guide).
The rotary screw compressor
The rotary screw compressor compresses air by two screws (rotors) that turn in opposite direction inside the housing. Air gets trapped between the rotors and is compressed. For a detailed explanation, check out my rotary screw compressor page.
Rotary screw compressors:
- Are low pressure (7 – 15 bar or 100 – 215 psi)
- Are high capacity
- Are designed for continuous use (24 hours a day)
Rotary screw compressor are big, industrial machines. They start at about 10 HP (7 kW) and go up to more than 1000 HP (700 kW). The biggest machine I have worked on was a 2000 HP (1500 kW) beast of an air compressor!
How to know what’s the right type of air compressor for you:
Get a reciprocating compressor when you need a small amount of air and don’t use compressed air continuously (for example in a workshop, for air tools). If you DO have some big tools that require a lot of air (but you use them only once in a while) it’s better to install a bigger compressed air receiver than to buy a bigger reciprocating compressor or even a rotary screw compressor.
If your compressor stands still more than 60% of the time, it’s often better to get a reciprocating compressor. Piston compressors don’t mind standing still (even prefer not to run all the time). But keep in mind that when you DO use compressor air, the capacity of the reciprocating compressor is big enough.
If you need high pressure (above 1500 psi), a reciprocating compressor is the only way to go. Screw compressors only go up to about 150 psi (10 bar) maximum.
Get a rotary screw compressor if you need air continuously. If you have a big workshop where compressed air is used all the time, or if you have a factory with one or more machines that use compressed air.
Rotary screw compressors don’t like standing still; it makes them rusty and old.
Reciprocating vs rotary screw compressors
|Pressure [psi]||up to 15.000 psi (1000 bar)||Up to 215 psi (15 bar)|
|Capacity [cfm]||from 1, up to 70 cfm||from 20, up to 500 cfm and above|
|Use||Workshop, contractor work, at home, diy||Bigger workshops, industrial use|
|Remarks||For intermittent use. Doesn’t mind standing still||For continuous use. Is happiest when it runs 24/7.|
Buying your air compressor
By now you should have a fairly good idea of:
- Which type of air compressor is right for you
- The pressure you need
- The capacity you need.
Now it’s time to go find that perfect air compressor for you!