A source of reliable, clean air for your spray guns is one of the main elements needed to get the professional finishing results we all want.
In this post, I’ll focus on air compressors (we’ll cover turbines in future posts) and show you the factors I consider most important when selecting one.
So let’s jump right in…
Key Factor #1: Air Volume Requirement. Selecting an air compressor starts with quantifying your total air volume requirement (measured in Cubic Feet per Minute or CFM, at 90 psi).
I have one air compressor dedicated to my spray booth (a separate one serves the rest of my shop), so that’s the example I’ll be using here.
Inside my booth are two air lines: one for spray guns, and another for my small air blow gun.
To perform effectively, the “thirstiest” of my four compressed-air guns require 15.2 CFM at 26 psi. And because I am using only one gun at a time (the air blow gun is only on for such a brief period, I’ll disregard its needs), my spray booth’s theoretical CFM demand is 15.2.
With a generous 20% overage factored in, the actual demand is 18.24 CFM, so my air compressor’s pump needs to be able to provide that volume of air.
Key Factor #2: Motor HP Rating & Duty Cycle. Some manufacturers exaggerate the horsepower ratings of their electric motors to attract buyers. But by using the rule of thumb that 1 HP can generate roughly 3.5 CFM at 90psi, you should be able to determine the approximate real HP requirements of any air compressor.
Another part of the discussion on motors is its duty cycle. A 5 HP compressor with a 100% duty cycle produces more continuous air than a heavy-duty 7.5 HP compressor with a typical 75% duty cycle. More is better!
Other Factors: Tank size, Electrical Requirements, Operating Noise. Let’s look at these one by one…
- Air Tank size/shape. A 60 US gallon tank is a good size for most one-operator spray booths. If your shop’s demands are beyond that, your supplier should be able to help you select one that best meets your needs. In a similar manner, if the only location for your unit is in a low ceiling mezzanine or other restrictive space, remember that air tanks also come in horizontal configurations. And if you’re planning to locate your compressor in an out-of-sight location, consider installing an auto drain system to help ward off tank rust-out.
- Electrical Requirements & Connection. Before selecting an air compressor, consult with your electrician. They should know the local codes and your unique situation and can therefore determine if your shop’s existing power panel is able to handle the load, as well as to give you an estimate on any electrical installation work.
- Operating Noise. Air compressors are noisy machines, some more than others. Installing sound-deadening insulation in the room where your compressor will be located will mitigate this factor, however there are cases where this may not be practical. Many manufacturers provide the decibel (db) ratings of their machines, so if noise is a factor, this information should help in your selection.
A well engineered and manufactured air compressor that is sized uniquely for your compressor-based spray guns can make all the difference in the quality of your finishing products. If you’re about to take the plunge and purchase a new air compressor, I hope this information will prove helpful.
Any comments or questions about this article…or requests for future topics? Please share your thoughts or see what others are saying in the comments section below…and I’ll respond to as many as I can. I’m here for you!
– Marty Schlosser