Choose an Air Compressor

Choosing an air compressor can leave you feeling lost if you don't know what to look for. That's because air compressors power a wide range of tools over a wide range of applications. In order to get your air supply right, you'll want to arm yourself with the right knowledge. Here's how to do just that.

Steps

Knowing the Basics

  1. Analyze the requirements of the air tools that you will be using. Are you going to be using the compressor for industrial use to power heavy-duty machinery, or will you use the compressor around the house for odd jobs like powering a caulking gun or inflating tires? You'll probably want a piston compressor with a tank if you plan on industrial use, while you may want a portable compressor without a tank if you plan on merely using it around the house.
    • In particular, consider pressure and volume requirements of any tools you may be using. Obviously, heavy-duty tools require much more pressure and, in turn, more volume. If you fail to choose a compressor that's large enough for your intended use, you will find yourself periodically waiting for the tank to fill up, thereby decreasing your work efficiency.
    • If the portable air compressor is for airbrushing, for example, a {{safesubst:#invoke:convert|convert}} tank capacity and around 30 psi of sustained air pressure would be adequate.
  2. Choose between piston-type and portable compressors. Essentially, there are two different kinds of air compressors. Piston-type compressors rely on a motor which builds up air pressure when it gets depleted. These store compressed air in tanks. Portable compressors do not have tanks, and so much stay running continuously in order to deliver air.
    • Piston-type compressors come in two varieties. The single-stage compressors use only one piston to compress air and top out at about 150 psi.[1] Two-stage compressors use two pistons to deliver near continuous air pressure, and top out at around 200 psi.[2]
    • Single-stage compressors are adequate for more heavy-duty applications at home. Two-stage compressors are more often used in industrial settings where owners expect near continuous usage.
    • Portable air compressors are more viable for light home use. Powering caulk guns, spray guns, glue guns, as well as for inflating small tires and rafts.

Making Specific Determinations

  1. Look at the horsepower (HP) of the air compressor. A common range for horsepower on an air compressor is between 1.5 and 6.5 HP. Air compressors with larger HP capacity exist, but are usually reserved for industrial uses and offer far greater psi.[2] Small-scale uses won't require as much horsepower as industrial uses.
    • While horsepower is a valuable marker in determining your air compressor, it shouldn't be the only one. More valuable will be a CFM rating, or Cubic Feet per Minute, if you can find one. Read more below for a detailed discussion of CFM.
  2. Try to look at Cubic Feet per Minute, or CFM. CFM is a measure of volumetric flow. Easy enough, right? The difficult part is that CFM changes depending on the psi of the compressor, meaning that two tools with different psi won't necessarily have CFMs that you can simply add together, which is what you want to be able to do. This is where things get tricky. Let's try to keep it simple:
    • Look for or ask about Standard CFM (SCFM) when evaluating compressors. Standard CFM is measured as 14.5 PSIA, at {{safesubst:#invoke:convert|convert}}, with 0% relative humidity.[3] (If you choose not to use SCFM, be sure to use CFM numbers that are all pegged at the same psi.)
    • When you've got the SCFM of all your air tools that you'll be using simultaneously, add up their SCFMs, then add 30% to that as a safety buffer. This should give you the maximum required CFM usage you'll need to complete the job. When choosing an air compressor, you want to get close to this number so that you don't waste time with a too-small unit or waste money on a too-large one.
    • Say, for example, that you're using a grease gun (~4 CFM @ 90 psi), framing nailer (~2 CFM @ 90 psi), and dual sander (~11 CFM @ 90 psi) at approximately the same time. Add all the CFMs to get 17 CFM @ 90 psi as your max required CFM.
  3. Consider space and portability. For example, will you be able to roll the compressor or lift it off the ground if you need to? Air compressors can be small, portable items or larger, more powerful fixtures. Portability is convenient, but if it will stay in one corner of the garage, you may be able to use a longer hose, instead, and have a higher capacity compressor. Essentially, does this compressor need to supply a nail gun on the roof, or just fill tires in the garage?
  4. Consider your power source. Will you have the luxury of electricity at all times, or will you be in environments without electricity. If you'll be next to an outlet at all times, it's best to choose a drive system with an electric motor. If not, you'll be forced to drive the compressor via a gasoline engine.
    • Most electric air compressors will run on 110V (US), but some larger ones run on 240V. Find out before you make the purchase.
  5. If using a piston-type compressor, determine how large your tank should be. If you'll only need your air compressor for short bursts of time — such as when using a nail gun — you can get away with having a small tank. If you'll be working for extended periods of time with your compressor, you'll want the tank to be bigger. Tank sizes are usually measured in gallons.

Tips

  • Oil lubricated compressors tend to last longer than oil-free ones and are quieter.
  • Aim for a slightly higher rating than you will need.
  • Don't forget hose length. Where will the compressor live in relation to the work area? If the compressor is in the garage and the work happens in the driveway, plan accordingly.
  • Work out your requirements, then look around for a compressor that uses them.
  • Pancake style air compressors have high pressure but low volume. Unless you need that level of portability, a small canister style may have a better volume.
  • Oil-free compressors may sound good in the store, but they may sound bad in your garage. Oil-free compressors can be very noisy, so be aware before you buy. However, they deliver purer air then oil lubricated ones.

Warnings

  • Air tools can be dangerous. Read and understand all manuals and be safe.
  • Avoid placing portable air compressors where they could fall.

Related Articles

Sources and Citations

  1. ↑ http://www.lowes.com/cd_Air+Compressor+Buying+Guide_875650869_
  2. ↑ 2.0 2.1 http://www.jennyproductsinc.com/howtochoose.html
  3. ↑ http://www.engineeringtoolbox.com/scfm-acfm-icfm-d_1012.html
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