Choosing the Right Air Compressor

Air CompressorWith so many options, sizes, and designs, it can be difficult to decide what air compressor is right for your needs. At Atlas Copco, we understand the struggle, and we are here to help. There are a few simple guidelines to follow and general questions to ask yourself when choosing the right compressor. Below you will find some helpful information that can take you through the process so that you have the perfect air compressor that fits your needs.

1. How are you using the compressor?
Depending on the work you do and the daily total amount of time you’ll be using your compressor, you’ll need a compressor that fits your workload. Are you using your air powered tools and equipment for just a few hours or are you powering them almost constantly until day’s end? Choose a compressor that will match your duty cycle to supply the correct amount of pressure throughout the day.

A piston compressor is excellent for intermittent work such as an automotive garage where a worker may be using air tools for just part of the day. In this application a rotary screw compressor would be too large and not the optimal choice.

Rotary screw type compressors are better suited for applications with higher demand so that they can run continuously.

2. Where will you place the compressor?
Air compressors require the right airflow in order to ensure proper cooling. Compressors cannot be placed in tightly enclosed spaces as this reduces the airflow and results in overheating issues and premature failure. Always design your compressor room with airflow in mind so that cool air can be drawn into the compressor and hot air expelled out of the room. Decide on the open space available to match compressor size and type.

If the compressor is outside, you’ll need to think about proper shelter or housing for the unit, since potential weather conditions might cause freezing or water damage.

Depending on where the compressor will be located, you may also need to consider the sound rating. Working in a loud environment for long periods of time, can be a health and safety risk for workers. Noise levels of compressors today can range from 40 to 92 decibels. Typically, rotary screw compressors are much quieter than piston air compressors.

3. What are your pressure requirements?
To know how many pounds per square inch (psi) of pressure you’ll need, determine the psi requirements of your biggest air powered tools or equipment. Something like a tire changer may take 150 psi, while hand tools could only require 90-100 psi. You will need a compressor that delivers pressure to match the largest demand. Equipment with higher psi needs may require a two-stage or multi-stage compressor to boost psi output.
Use regulators to lower the air pressure to those tools that do not require higher pressure. Using too high of a pressure when not required will damage tools and waste electricity.

4. What is your required air flow?
Free Air Delivered (FAD) is generally measured in cubic feet per minute (cfm). This is the amount of air flow the compressor can generate at any given time. It can be expressed through piston displacement (PD) or in actual cubic feet per minute (acfm). When choosing a compressor, make sure you are seeing the acfm measurement as this is the total amount of air available to do work. Most tools or pieces of machinery will have their cfm requirements specified, so use this information to properly size your compressor.

5. How much horsepower do you need?
The horsepower of a motor is more or less proportional to the cfm the compressor is capable of producing. Generally, the higher the horsepower, the more cfm it can put out. However, horsepower is not a good indication of your requirements. Your psi and cfm needs should be the main deciding factor as to which compressor is right for you. As technology improves, compressor companies have engineered ways to get more cfm per horsepower. If you are upgrading to a newer compressor, you may actually be able to buy a smaller horsepower compressor and save yourself money both on the purchase and every month afterwards with lower electricity bills.

6. How big should your tank be?
Tank size determines how much pressurized air is at the ready at all times. Larger tanks require the compressor to run less to meet the minimum pressure needed in the system. Smaller tanks will run more as air is used to replenish the amount of pressurized air available.

Tanks can be vertical or horizontal. This doesn’t affect the capabilities of the air compressor, but will affect the amount of physical space they take up. Vertical tanks are preferred in smaller spaces, while horizontal tank compressors are generally fitted to larger horsepower compressors.

A rule of thumb is that for fixed speed rotary screw compressors, you should purchase 4 gallons of tank per cfm of air produced by the compressor and 1 gallon per cfm for VSD compressors. For piston compressors, larger tanks will allow the compressor to cycle less often. A larger tank is not a replacement for a larger compressor so if you find your piston compressor running more than 60% of the time, it’s time to start looking into upgrading it.

7. What additional features should you think about?
Compressors come with a wide range of optional features to fit requirements that are more demanding. Some options to think about include heavy duty drive-trains, better cooling capacity, oil free or oil less air, pre-filters for air intake, variable speed drive motors, multi-stage compression, stainless steel or cast iron construction, high ambient temperature variants, and many more. Discussing your specific needs with a sales representative will provide a better idea of the options that are right for you.

8. What are the compressor’s electrical requirements?
In order to ensure the air compressor will run properly after installation, you need to make sure the power available where it is used matches the power requirements of the machine. The standard residential electrical voltage is 110v single phase. In most cases, 110v will only power a compressor up to 3 horsepower. 230v single phase is commonly used for compressors up to 5 horsepower. It is also important to understand residential and light industrial is generally limited to single phase power. In the United States the power available is typically available only in 60hz and written in the (voltage/phase/frequency) nomenclature:

Single Phase





Three Phase





We recommended having a professional electrician determine electrical requirements before purchasing and installing an air compressor.

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