Air Compressors

We do not recommend that you use a generator to power your compressor if no power is available at the jobsite. Serious damage can be done to your compressor motor when sudden fluctuations in power from a generator occur. This is considered improper usage and will usually void any warranty on the compressor. It is easy for the manufacturer to find damage that occurred because the compressor has been run on a generator.

SUGGESTION: You may want to consider using a gas-powered compressor when there is no power supply available, or the power supply is too far away. Also use the suggested length and gauge of power cord as noted in the user's manual. 

We need to define what we mean by "stop-start" and "constant-run":

Stop-Start: This means that a pressure switch is used to automatically turn on and off the compressor at designated low and high-pressure levels. When switched on, the pressure in the tank builds to a certain psi (pounds per square-inch) and then automatically turns off. When air is used, the psi in the tank is reduced and eventually reaches a low setting where the pressure switch automatically turns back on to build psi back to the high point. This operation is common for smaller electric, direct-drive compressors and some smaller wheelbarrow electric compressors.

Constant-Run: This means that the motor continues to run and as a result continues to turn the pump. When the tank reaches the high-pressure setting, a pilot unloader-valve opens to atmosphere so that the compressor can continue to run. The valve will close again when the psi is at the low point and begin to direct air back into the tank and re-build to the high-pressure point. This setup is used more often when using tools that require a heavy and constant flow of air without interruption, such as a grinder or sander or sprayer.

(NOTE: Normally if a compressor stops and starts more than 20 times per hour, you need to use a constant-run setup. If not, you are in danger of ruining the motor due to excessive heat buildup. Stopping and starting so often creates a huge amount of heat, more than if the motor stays running all the time.)

You can find compressors that have a "dual-control" option built on to the compressor where you can switch back and forth between stop-start and constant-run depending on the situation.

All gas-powered compressors are set up with this unloader-valve system because an engine cannot stop itself and start up again. It will only idle-down and speed-up at set psi levels via a throttle-control mechanism.

The answer is no. When an air compressor is built, it requires an engine to power the process of producing air. The horsepower is not the only component of the equation. It 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. Remember to keep your required cfm in mind. Horsepower does not make you work more efficiently. What does is horsepower working in unison with a quality pump that produces enough cfm for your needs.

All reciprocating compressors have a series of pistons that pump up and down inside their individual cylinders to compress the air to a higher pressure. This rubbing creates friction, which creates heat. In order to conserve the life of the pump, you need some type of protection. Some pumps are "splash" lubricated with oil and some have a Teflon-type lining in the cylinder.

Oil-less compressors are adequate for lighter use applications and have the advantage of being able to run off-level without worry, however even though they are considered low-maintenance, they tend to wear much quicker due to more heat build-up and repair costs could be extensive.

Oil-lubricated compressors have the advantage of keeping the pump running cooler and lasting much longer and are built for the professional who takes pride in ownership and will maintain his equipment. However the key is to make sure the compressor sits level so the "splash"-lubrication is effective and reaches all cylinders. If run off-level, it can score the cylinder and do heavy damage over a short period of time.

First, you must figure out your tool's air requirements. This can be done by knowing the air requirements or cubic feet per minute (cfm) of the tools you are using or plan to use. 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. This can be found on the tool itself or in the owner's manual supplied by the tool manufacturer.

Second, determine air requirements one tool at a time. If you are the only person using the compressor, you should find the tool you will use that requires the largest cfm. Use this cfm to determine the size of compressor you need. If more than one tool will be used at any one time, add up the cfm for all the tools that will be used at the same time (from largest cfm to smallest) and use this total cfm to determine the size of the compressor you need.

Note: If your tool operates well below or above 10 psi, you should keep in mind that as you drop in PSI usage you get a slightly higher cfm and vice versa.

Tank size only becomes a factor for one reason - a larger tank for air. A 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. I would only go with the bigger tank if I am concerned about the motor starting and stopping too often, or if I know that I will need a constant flow of air in longer intervals. You have a choice between a larger tank and a constant-run unit.

Most direct-drive electric compressors can run on a standard 110-volt circuit. When you get into the electric wheelbarrow compressors, you may have a choice for a dual-voltage option, which allows you to switch between 110-volt and 220-volt, depending on power supply that is available for the job. However, for jobs that require substantially more air, usually a 220-volt motor will be your only choice if a gas-powered compressor is not allowed as an option. When looking for a stationary shop compressor, you need to know what power supply you have at your disposal (208v, 230v, or 460v), and whether it is a single-phase or three-phase power. These units are usually hard-wired into the power supply and require a magnetic starter for thermal overload protection.