The Basics for Choosing the Right Air Compressor
There is a lot of confusion out there about selecting the right
size air compressor to run your air tools. Basically, there are
several factors to look at when choosing the proper air
compressor for your shop or garage. The first criteria is horse
power rating. Most people assume the higher the horsepower
rating on the box, the better the air compressor. However, all
horse power ratings are not created equal and can easily be
misrepresented. What I mean is, you go to your local giant
hardware retailer to pick out a new air compressor to run your
impact wrench. They have a 5 hp unit that is priced really
cheap. Why is that 5 hp industrial unit cost so much more? 5 hp
is 5 hp, right? Not necessarily. Let me explain. Look at how
much power the hardware store unit draws. It probably needs
around 15 amps from a normal 110 volt circuit. At this rating,
you are really getting only 2 hp. The 5hp rating on the box is
inflated. To really produce true 5 hp you need at least 24 amps
from 220 volt circuit to get it. If you are looking for 5 hp
electric compressor, buy the industrial unit and stay away from
the cheaper unit at your local hardware store. I am not saying
that every air compressor at your local hardware is junk. A lot
of times one of those units is all you need. Just be aware of
the true horsepower rating. The next consideration when
purchasing a new air compressor is, "How much PSI will I need?"
For the newbies, PSI is short for "pounds per square inch" and
this is how most compressors in the US are rated. In Europe, you
will see them measured in bars. PSI is all you need to worry
about on this side of the Atlantic. Most of the commonly used
air tools require about 90 PSI to operate correctly. However,
you will still need a compressor with a higher shut-off
pressure. Most air compressors that you find at the local
hardware giant are "single-stage" and shut off at 125 - 135 PSI.
Don't let that fool you. You might think all you need is 90 psi,
so that should work just fine. Generally, these light duty
compressors shut off at 100 psi and don't forget about pressure
loss in the line. The little light duty compressor will barely
run an impact wrench. It might be fine for light duty garage
use, but if you really intend use your air tool, more is
definitely better. Many industrial compressors are "two-stage,"
which means they build up to shut-off pressure in two stages.
The first stage builds to about 90 PSI and the second stage
builds to 175 PSI. The next rating criteria for air compressors
is CFM. CFM stands for "cubic feet per minute". It is a
measurement of volume. Basically it is how much air is being
moved. Air tools require a certain amount of air volume to run
on. PSI is just part of equation. Don't be confused by different
CFM ratings at different pressures. Every manufacturer is trying
to make their product look better by giving higher CFM ratings
at different pressures. The only real concern is how much CFM
you will get at 90 PSI. Remember 90 PSI is what most air tools
require to operate. To find out what your air tool needs to run,
just look on the box for the manufacturer