Air Compressors Buying Guide
Air compressor power air tools, also called pneumatic tools, are generally faster, lighter and more powerful than traditional power tools. The key to choosing the ideal compressor is to match the unit to the job demands. Portable compressors are ideal for the home and the job site while stationary compressors provide the high volume of air needed for powering automotive and production air tools.
This buying guide will explain the factors to consider when selecting an air compressor, so you can feel confident you’re choosing the right compressor for your needs.
Safety: Never exceed the recommended pressure for the job or the tool. With oil-lubricated compressors, always check the oil level to ensure sufficient lubrication. Make sure safety relief valves are not covered during use, as they allow air to escape automatically if pressure is too high. When done, open the drain to get rid of moisture.
Air compressor units fall into two broad categories: portable and stationary.
|portable air compressors||stationary air compressors|
|Description||Available in a variety of shapes and sizes Smaller models are light enough to carry, larger models include wheels Available with different sized tanks ranging from 2-6 gallons to 20-30 gallons to handle light to demanding jobs||Designed to be bolted into a fixed area and wired directly to a building’s electrical circuit Typically feature 60 to 80 gallon tanks and 4 to 10-horsepower motors Ideal for garages and workshops|
Air compressors are either powered by electricity or gasoline.
Electric compressors generally run on standard household voltage, between 110–120V. Compressors with motors that exceed two running horsepower require a 220–240V outlet. Since electric compressors don’t emit fumes, they are the better choice for indoor applications. Remember that powering an electric compressor with a generator can damage the motor.
Gas-powered compressors are generally used by builders and remodelers because of their high output and convenience at the job site. However, these compressors emit exhaust and should only be operated outdoors or in well-ventilated work areas.
The most important rating to consider when matching a pneumatic tool’s requirements to an air compressor’s capabilities is how much air the compressor can deliver, which is measured in Standard Cubic Feet per Minute, or SCFM. Tools powered by air compressors also have SCFM ratings, which indicate the air flow required for optimal operation.
The actual SCFM changes depending on the pressure of the air in the compressor (represented as pounds per square inch, or psi). Look for the “SCFM at 90psi” number when comparing SCFM ratings.
Smaller tools usually require between 0-5 SCFM, while larger tools can require 10 or more SCFM. To gauge the minimum compressor SCFM rating you need, examine the SCFM requirements of all the tools you intend to use. Multiply the highest tool rating by 1.5 to get the minimum compressor SCFM for your needs. This gives you a little buffer, which is important, since actual SCFM varies during compressor operation.
If you expect to operate multiple pneumatic tools at the same time, you’ll need more power. In this case, calculate the minimum SCFM compressor rating by adding up the SCFM requirements for each tool that you’ll use simultaneously. Most light-duty home compressors are designed to power only one tool at a time, but larger professional-grade compressors can handle multiple tools.
The air pressure the compressor generates inside the tank is measured in Pounds Per Square Inch, or PSI. Light-duty compressors generally have 90 psi, which is typically sufficient for pneumatic tools for simple household tasks, including nailers. More powerful compressors may generate 150 psi or higher.
While not as important as the SCFM rating, a compressor’s horsepower (HP) rating can give you a relative sense of the model’s power. Horsepower indicates how powerful the motor is, while the SCFM rating tells you how much power the compressor actually provides to your tools. Compressors generally have horsepower ratings between 1.5 - 6.5 HP.
The size of a compressor’s tank determines how long air tools can run before the compressor turns back on. Tank sizes are rated in gallons, and run from 1 gallon all the way up to 80 gallons.
If you will be using air tools that require a high volume of air for continuous use, then you should consider a larger tank. If you only intend to use the tool intermittently, your compressor can have a smaller tank size. Having a large enough tank with a compressor pump that exceeds the SCFM requirement of the tools will allow the compressor time to cool between cycles.
Tools that require only quick bursts of air, like pneumatic brad and finish nailers, drain the air tank much more slowly. For these tasks, tank sizes between 2 to 6 gallons are sufficient.
There are two pump types: single and two-stage. You may also choose oil-lubricated or oil-free. In addition, there are other features that can protect both you and the compressor from harm and unnecessary wear and tear.
Compressor Pump Types
- Single-stage compressors can have one or more cylinders producing compressed air at the same output pressure.
- Two-stage compressors have at least two cylinders. The first-stage cylinder(s) feed air to a second-stage cylinder that further compresses the air. The second stage cylinder(s) typically increases the tank pressure to around 175 psi. The benefit is more air stored in the same size tank, allowing tools to run longer. This is useful for high-demand work, such as continuous tool operation in an auto shop.
- Oil-lubricated compressors require oil to operate, just like a car or lawn mower engine. The oil lubricates the moving parts in the pump to prevent excessive wear. They are generally larger and heavier than equivalent oil-free models, and oil must be monitored and changed to prevent premature failure.
- Oil-free compressors typically use special piston rings, made from a material similar to what's used in non-stick frying pans, to lubricate the cylinder. Because there is no oil, oil-free compressors are much smaller and lighter than oil-lubricated compressors, making them a popular choice for home and job site applications where portability is important.
- Air-Cooling System: Cools pumping machinery to extend motor life.
- Thermal Overload Switch: Automatically shuts off motor if it overheats, increasing tool life and protecting your investments.
- ASME Certification: Indicates high-quality material and craftsmanship, identified on the tank with a certification label stating that the unit meets the standards of the American Society of Mechanical Engineers.
- Roll Cage: Protects the compressor from being crushed or battered on the job site.