An Air Compressor Buying Guide For Home Use Air Compressors
Why buy a home air compressor?
A small air compressor can be one of the handiest tools in the workshop, but some care or guidance is necessary when buying one. The rated horsepower, amperage and CFM are all important, along with some other considerations. Air compressors can range from a tiny airbrush compressor to monsters that require a tractor trailer to contain them, and physical size is important to people with limited space.
The primary consideration (aside from cost factors) is the intended use of the compressor. Will it be used to paint with, operate an air nailer, or just fill a few tires or kids toys? Do you expect to run the compressor 20 hours a week or 20 hours per year? Air compressors are typically noisy tools - will it be used in a basement workshop, a garage or separate building? Will the compressor be expected to operate multiple tools at the same time? All valid considerations that should help guide you in buying an air compressor.
Airbrush air compressors are the smallest of the group, designed almost exclusively for use by airbrush artists. Nevertheless there are still basic considerations to be made.
Possibly the first is noise. Nothing is worse than sitting quietly, working with your airbrush on a small detail, when suddenly the compressor blaaatttsss into operation. As a disturbance to concentration not much could be worse. As a general buying guideline, buy the quietest compressor you can for airbrush work.
Any oil or water that gets into the air supply will ruin the paint job; fish eyes throughout the work are seldom desirable. Buy an oil less compressor unless a very large compressor is needed. A water trap is very often necessary to catch the inevitable water produced by all compressors.
Make sure the compressor has at least a small pressure tank to "smooth out" pressure fluctuations. Most small compressors are the piston type, which produced surges of compressed air; a tank will reduce the surging effect of the air compressor considerably. In general, the larger the tank, the better.
Most airbrush compressors will operate most airbrush kits. If you already have an airbrush gun, however, make sure that the volume of air produced (CFM) at the rated pressure (PSI) of your equipment will not stretch the capabilities of the compressor. A good suggestion is to buy a compressor capable of producing at least twice the volume air requirements of your airbrush.
Workshop air compressors
An air compressor for your workshop can range in size from a small "pancake" style that can be carried in one hand to a large, vertically mounted, unit that cannot be moved without considerable difficulty. In the middle are those units that are fairly large, but are equipped with a handle and wheels for easy transport. They can be moved around the house or garage without undue difficulty, yet provide enough compressed air for most jobs. My own air compressor is listed as a 5 HP compressor, producing nearly 7 CFM at 90 PSI, and is mounted horizontally on a wheeled base with a handle. It is pictured to the right, and is one of the more useful tools in my workshop.
Oil less compressors, as noted above, are a virtual requirement if you wish to use it for any painting. Oil filled compressors, on the other hand, are generally larger and intended for heavier duty use. Oil separators are available for these compressors, but a good separator will add considerably to the cost.
The primary factors, other than oil use, are listed below:
- HP. This figure can be used only as a guideline, as the method of figuring horsepower has changed in the last decade or so to advertising "peak horsepower" or some other figure that has little to do with the actual usable power. In general, a 1 HP compressor is quite small, while a 5 HP or larger compressor is about as large as can accommodated without the use of a 240 volt dedicated circuit to power it.
- CFM, or SCFM. This is the "standard cubic feet per minute" of air that the compressor will produce at the specified pressure. Most air tools will require less than 3 CFM, while many paint guns (particularly cheaper ones) will require much more. Make sure that this figure is adequate for the tools you intend to use with the air compressor.
- PSI. Pounds per square inch, this is the maximum pressure the air compressor will produce. Most home use compressors should be able to produce 120 PSI - while that pressure will seldom be used, 90 PSI requirements are not that uncommon.
- Storage tank size. A good sized air storage tank is necessary to not only smooth out the pressure variations produced by any compressor, but also to prevent the compressor from constantly starting and stopping. A tank that is too small can result in a compressor that must start and stop every few seconds instead of several minutes. My own tank is a 20 gallon size, which is probably over sized for most home compressors, but means that the compressor only runs for a short time every 5 or 10 minutes under heavy use.
- Vertical or horizontal use. The tanks are generally designed for use in either the horizontal or vertical position, with the compressor mounted on top. This is primarily a function of the space and room available to them; choose one that fits the room you have.
- Amperage. Most home air compressors will operate fine on a dedicated 15 amp electrical circuit, but larger units may require either a 20 amp 120 volt circuit or even 240 volts. My own compressor can operate on either 120 or 240 volts by re-wiring it internally which is fairly common in the larger home units. I have left it on 120 volts so that I can still move it to different locations and still plug it in. It requires 15 amps, which makes a 15 amp circuit really marginal, but it works and is plugged into a dedicated 20 amp circuit when still in the workshop.
Air compressor accessories
No air compressor buying guide would be complete with at least some discussion of accessories. The variety is virtually unlimited, from blow nozzles to air impact wrenches suitable for removing truck tires.
Every owner will need air hose. Buy only a good quality rubber hose - plastic hoses will not last. The minimum size for longer (25 foot) hoses is 3/8" - don't settle for a 1/4" hose as it will not carry a sufficient volume of air for many tools.
A collection of quick connect fittings to quickly and easily change tools will be necessary. A female end will be needed for each air hose, while each tool should have a male fitting.
One of the most obvious needs is a fitting to fill car tires; additional fittings for toys such as basketballs or pools is also very desirable and quite inexpensive. Make sure you have both a fitting to fill the car tires as well as a tire pressure gauge. Properly filled tires result in better gas mileage and increased tire life. This fitting alone could pay for the air compressor over time.
Various tools such as nail guns, brad nailers, sanders, wrenches; the list is endless and must be customized to each person and the type of work they perform. A few examples are given here, but don't stop with them; use your imagination. Most electric tools are duplicated in pneumatic power source tools, as well as many that really have no electric counterpart.
Having said that, there are tools that should probably not be pneumatic. Most of a small homeowners tool sets are hand tools only, and even the few power tools most homeowners own, such as a cordless drill, should be left as they are. A pneumatic workbench makes no sense, but what workshop would be complete without a workbench? While there are jobs that are much easier and quicker with pneumatic tools, there are also tasks like wood joinery that need specialized electric tools.
© 2010 Dan Harmon