<VV> Harbor Freight/Central Pneumatic

[Bob Lindsey]

Excellent info from John.  The only thing I would like to point out, if you
look at the compressors at a dealer (bought my 7 hp. unit from Lowe's last
winter) you should see a convenient chart showing the various air tools SCFM
requirements.  Handy little reference.

Bob Lindsey

Re: <VV> Harbor Freight/Central Pneumatic


> At the risk of starting a long thread about compressors, here goes:
> There's a lawsuit going on now about the way the compressor manufactures
> rate their motors.  Most 'home' compressors are rated at 'peak'
> horsepower.  The Harbor freight unit is rated this way.  I don't know
> about the Lowes unit, I couldn't find it on their website.  Peak
> horsepower is basically 'stall horsepower'.  The motor isn't turning, but
> is developing a lot of torque just before the fuse blows.  Obviously, it
> can't pump any air when it isn't turning.  The amount of air you need
> depends on the rating of your tools, and how continuously you use them.
> A small tank 1 hp compressor will run an air chisel (for about 15
> seconds) and won't be satisfactory for that use. Ditto for an impact
> wrench.  It probably won't be able to remove the lug nuts that you
> tightened by hand last year.  I have a Coleman compressor from Home
> Despot that says 5 HP, but the amps rating on the motor calculates out to
> 2.2 hp.  7.1 CFM @ 40, 5.7 CFM @ 90.  It is adequate for small tools and
> air chisels, but is nearly useless with a 1/2 inch drive impact wrench.
> My electric impact wrench is much better.  Trouble is, the air compressor
> was bought to match the impact wrench rating.  somebody is lying here.
> Either the compressor doesn't put out the volume it is rated at, or the
> impact wrench uses more air than it was rated for.
>
> The real way to compare the output of compressors is to look at the CFM
> ratings.  SCFM stands for standard CFM, where the output is corrected to
> some industry standard.  It is probably a more reliable figure than
> (nonstandard) CFM.
>
> The Central Pneumatic compressor is a direct coupled compressor.  In the
> picture is looks to be a single cylinder unit.  I don't like these and
> prefer a belt drive with at least two cylinders.  I believe the belt
> drive compressors last much longer in use.  Of course, home use is easier
> on tools than industrial use, and you might not use it up for a long
> time, so it's your choice.
>
> Horsepower, if I remember my numbers right, is (volts * amps)/748.  Check
> the label rating to see what the actual horsepower is, so you'll know how
> badly you are being cheated, but go by the CFM ratings.  Occasionally, a
> unit that goes up to 150 psi is really handy with that impact gun, but be
> sure to use a regulator to reduce the pressure, under normal use.
>
> Other things come into question.  If you have to pay freight from Harbor
> Freight, then factor that into the cost of the unit.  It may only come by
> truck to a dock.
>
> My preferences:  I like a belt driven compressor.  They are less noisy
> and tend to last longer.  'Oil-less' compressors are cheap disposables,
> and have to be rebuilt frequently.  Better to use an oil separator/filter
> unit if you are painting.  It's difficult to find a real workhorse
> compressor in 110 volts.  Yes, you can make do, but they are really
> horsepower (and CFM) limited.  My 5hp rated 2.2 actual hp compressor has
> to have a 35 amp circuit simply because of that 5 hp startup torque.
>
> Rules of thumb for air compressors:
> 1) Always buy a larger unit then you think you need.
> 2) A large tank helps by delaying the moment the compressor comes on, but
> also takes longer to fill.
> 3) Don't forget that next year you will buy a sandblast cabinet and need
> a lot of air.
> 4) If the wife says you can have an air compressor, don't tell her that
> there are smaller cheaper ones than the one you want.
>
> John Ryall