Thinking about buying an air compressor, but don’t know where to start? The choices can be overwhelming, so let us help you identify what you need from an air compressor. When selecting a compressor, consider its weight, size, portability, maintenance requirements and most importantly air flow.
The first thing you need to do is identify which projects you plan to use a compressor on. An air compressor with air tools can do an amazing amount of work around your home and shop, regardless of whether your chores include woodworking, metalworking, mechanical jobs or even simple home chores like inflating tires or sports balls. Remember to consider jobs you might take on in the future.
Once you know what jobs you plan on doing, you can determine what air tools you will use. Then you will need to figure out your tool’s air flow requirement which is measured in cubic feet per minute, or ‘CFM.’ Some tools consume more air than others. Tools such as pneumatic nail-guns and staplers consume smaller amounts of air, while air grinders and sprayers consume larger amounts. Most tools have a usage rating for CFM consumption at a recommended PSI. See the following chart for tools and their average CFM rating @ 90 PSI:
|Air Tool Description||Average CFM @ 90 PSI|
|Angle Disc Grinder – 7″||5-8|
|Impact Wrench – 3/8″||2.5-3.5|
|Impact Wrench – 1/2″||4-5|
|Impact Wrench – 1″||10|
|Mini Die Grinder||4-6|
|Ratchet – 1/4″||2.5-3.5|
|Ratchet – 3/8″||4.5-5|
Figure out your airflow requirements by adding up the CFM for all the tools that will be used at the same time, then multiply that by 20%. You need to choose an air compressor with a CFM rating that exceeds the amount of your total requirement.
While most air tools operate at 90 PSI, some air tools require less PSI and some, especially sanders and polishers, a higher PSI. Make sure the compressor you select has a max PSI rating above the highest rated tool you will use.
The next factor to take into account is tank size, usually listed in gallons. An automatic start/stop compressor will run until the pressure in the tank builds to its high-pressure point. Obviously, the bigger the tank, the longer it takes to consume the compressed air. However, the downfall is that once the air is depleted, it takes a lot longer for the air tank to refill with pressurized air. A constant-run, or continuous use compressor will run constantly. For this type of compressor you can utilize a smaller tank as long as the pump and motor can keep up. For intermittent use, you can save money by choosing an air compressor with a smaller pump/motor and a larger tank.
If your primary usage is in short quick concentrated bursts, then a tank size of up to 6 gallons can be used. Go with a bigger tank in the range of 7-30 gallons if you are concerned about the motor starting and stopping too often, or if you need a constant flow of air in longer intervals. For tools that use a large amount of constant air flow like sanders, then a 30-60 gallon or larger tank is advised.
One factor that is not as important is horsepower. A motor or engine has to be combined with the compressor pump that it runs to produce the air needed. The bigger the horsepower does not necessarily mean more air. Horsepower does not make you work more efficiently, but horsepower working in unison with a quality pump that produces enough CFM for your needs.
The power source of the compressor is very important to understand. If you want to run your compressor on your household circuit, you just need to check that the compressor operates on 120 volt, 15 amp circuit. Most compressors up to 30 gallons operate on your household circuit. Larger compressors need more power to operate. Generally, compressors larger than 30 gallons operate on 240 volt, single-phase power. Two-stage compressors (10 hp and larger) operate on three-phase power only. If no electrical power is available, you will need a gas-powered air compressor.
The tank design or style is also something to consider, because what you own, you must store. Hand-carry units come in a round flat ‘pancake’ design, a single ‘hot dog’ tank design, or feature twin tanks, giving the compressor a box-like shape. Portable tanks have wheels and are designed either horizontally or vertically to occupy a smaller footprint. Larger tanks are usually stationary or might be available in a portable wheelbarrow style. On tanks that you will move around consider the weight. Also remember that the material the tank is made with will affect its weight.
Another thing to think about is noise level, which is measured in decibels. Compressors in the 90 db range are really loud. Quieter compressors are around 70 decibels.
Maintenance is something else to take into account. Oil-free compressors have sealed bearings and require less maintenance than oil-lubricated compressors. Oil-free compressors usually have enough power for homeowner applications, however are often loud. Most heavy-duty, professional-grade compressors are oil-lubricated, but these compressors require regular oil changes.
Air compressors are also available as single-stage or two-stage models. Single-stage models are the most common for home usage. Two-stage compressors are usually found on commercial heavy-duty compressors, but are good choices for continuous-use applications.