Anyone who is going to use air tools is going to need a compressor. It doesn’t matter if they are using an impact wrench for mechanic’s work, an air nailer for construction, or any other pneumatic tool, without a compressor to power the tool; it’s going to do no more work than be a paperweight. The right air compressor is just as important as the tools that it is going to power.
So, how do you select the right air compressor? For a lot of people, it’s just a matter of looking over the compressors available, and picking out one they like. However, this is kind of a haphazard way of buying an expensive piece of equipment. It’s better to have some idea of what one is looking for, before starting to look.
Gas vs. Electric
Most air compressors on the market are electric powered. They have to be plugged into a normal 120 VAC outlet for power. But, what do you do when there’s no electric power to run the compressor? In those cases many people have to use a generator to power their compressor. That’s just one more piece of equipment to carry around.
If one is working on a lot of job sites where electricity isn’t available, it’s a good idea to buy a gas powered compressor. That reduces the amount of equipment that needs to be dragged to the job site, and the gas powered compressor will be more fuel efficient than powering an electric compressor off of a generator.
When selecting an electric compressor, it is important to keep in mind the maximum current draw of the compressor. When the motor starts, it draws a surge of power. That’s the worst power consumption. If there’s ever a time when the compressor is going to trip a circuit breaker, that’s the time. Remember, most outlets are only on 20 amp breakers. Manufacturers keep this in mind with their designs, but a big compressor running off the same circuit as other equipment can still trip a breaker.
What do the Specs Mean?
While I suppose it’s possible to buy a compressor just based upon how it looks, that’s really not much of a criteria. You’ve got to understand what the specs are and what they mean. Here are the basic specs that you’ll be looking at:
Motor size – measured in horsepower (HP). Everyone likes to brag about the horsepower, but it really doesn’t mean much of anything. The only time it comes into consideration is when comparing two compressors which are otherwise equal. The higher horsepower compressor doesn’t have to work as hard, so it will probably last longer.
Tank capacity – measured in gallons. This is somewhat important. The larger the tank, the longer your air tools can run off of the “bottled” air, before the compressor needs to turn on again. You don’t want the compressor running at any more than a 60% duty cycle, or there’s a good chance the motor will burn out. More than anything, tank capacity is a convenience. If you are running tools that consume a lot of air for several minutes at a time, with rest periods for the compressor to recover between times, a larger tank helps. Likewise if you have several people working off the same compressor.
Weight – measured in pounds. If the compressor is a portable unit, this is important. Some of these babies can be heavy enough to really mess up your back if you try and pick them up. For mobile operations, like construction work, a lighter weight compressor is helpful.
Max pressure – measured in pounds per square inch (PSI). This is not very important, as pretty much every compressor on the market provides more pressure than air tools need. As long as the compressor will produce 120 PSI, you can run almost anything on it. There are a few high-power tools which require more than 120 PSI; in those cases, you need to pay attention to this specification.
Air capacity – measured in cubic feet per minute (CFM). This is the single most important specification on any air compressor, and for some reason most manufacturers hide it in the small print. This is how much air the compressor is able to compress at a particular pressure. Typically, manufacturers will rate their compressors at two different pressures, 40 PSI and 90 PSI. As there aren’t any air tools which use only 40 PSI of air, that really doesn’t mean much, it’s the 90 PSI figure that counts. This is critical information, as the air capacity of the compressor must be higher than the air consumption of the tools that will be attached to it.
Air Compressor Styles
There are several common styles of air compressors. While they all pretty much do the same thing, the form factor is different, intended to be used in different ways.
Pancake – These compressors are small units, typically with a six gallon round tank. They are compact units, which makes them very popular with contractors, for powering air nailers. The Porter Cable C2002WK is a popular model of this style compressor.
Hotdog Portable – These are very small compressors, designed for high portability. Typically the tank is only one or two gallons. Like the pancake, they don’t have wheels, but are light enough to carry. The Senco PC1010 is a good example of this type of compressor.
Twin Tank – These are another compact compressor style, designed to be carried. The major difference between one of these and the hotdog is that it has more tank capacity; about twice what the hotdog has. Gauges and controls are mounted on a control panel, for those that like that. They usually have two air chucks, as opposed to the single chuck that most compressors have. The Makita MAC2400 is a good example of this style.
Wheelbarrow – Wheelbarrow compressors are twin tank units with a single wheel. Handles at the other end allow the compressor to be moved much like a wheelbarrow. These are higher capacity units, with much larger tanks, somewhere between 5 and 8 gallons total capacity. The Hitachi EC2510E is an example.
Horizontal – This is the “standard” compressor design, with wheels at one end and a handle at the other to move it around. Horizontal compressors vary incredibly in their capacity, with tanks all the way up to 20 gallons. The larger ones can power two to three air tools at a time. The Campbell Hausfeld HL540100AV is a great example of a horizontal compressor.
Vertical – Vertical compressors are not designed to be portable, but are rather shop compressors. By turning the tank vertically, the compressor takes up less floor space in the shop. These are high capacity compressors, with tanks up to 40 gallons in size. They are intended for use with multiple air tools at a time. DeWalt’s D55168 is a small vertical compressor.
As I’ve already mentioned, the most important specification on an air compressor is the amount of compressed air that is produces. If a compressor can’t produce enough air to power the tools being connected to it, it is essentially worthless. This table should help in determining how much air capacity you need in your compressor. Keep in mind that these are approximations; you need to check the actual specifications of the tools you are going to use, as specifications can vary.
Air Consumption in CFM
4 – 22
|Air motor, 1 hp||
15 – 15
4 – 10
|Die grinder, one-quarter inch||
4 – 6
|Disc grinder, 7 inch||
3 – 6
|Impact wrench, one-half inch||
4 – 5
|Impact wrench, one inch||
|Mini die grinder||
4 – 6
8 – 16
|Paint sprayer, handheld||
3 – 7