At 06:23 PM 7/2/2008 -0700, Ron King wrote:
>In the market for a stationary air compressor, and wondered if
>anyone had personal experience/thoughts/opinions? Usage will be
>mainly automotive but haven't ruled out the occasional spray paint
>job which I understand takes more CFM as well as PSI.
Find half a dozen air compressor tech articles starting here:
http://mgaguru.com/mgtech/tools/ar101.htm
If you are contemplating auto restoration, sanding, grinding,
painting, etc, a real 2-HP belt driven compressor is a nice size for
a home shop. 2-HP is that largest motor that can run on a 120-volt
20-amp circuit (with a 15-amp plug), drawing about 13-amps under full
load, slightly higher on startup. Most of the 2-HP motors can also
be wired to run on 240 VAC drawing half the current. Do not be
fooled by the "peak horsepower" marketing ploy. If it runs on a
120-vac 15-amp line cord it cannot be more than 2-HP.
A real 2-HP slow running belt driven compressor can put out about
9-CFM at 40-PSI, and a bit more than 7-CFM at 90 psi. Common paint
sprayers need about 8-CFM at 40 PSI (or less), so a 2-HP compressor
can give continuous operation of a spray gun. A small die grinder or
2-inch angle sander can run near contuinuous at 90-PSI. A larger die
grinder or 3-inch cut off grinder can run 50% to 70% duty cycle at
90-PSI. A dual-action sander might run continuous at 40-45 PSI in
orbital mode, or 50% duty cycle at 90-PSI in high speed circular
mode. Running an air ratchet or impact wrench or inflating tires are
intermittent operations that need large flow for short time, no
problem at all. I have run my home shop for decades on a 2-HP
compressor and seldom feel the need for more air.
If you're thinking about running a sand blaster continuously you
would need at least a 5-HP motor running on 240-VAC with a 2-stage
compressor, and same for a high speed circular sander. A real 5-HP
2-stage compressor can do 15 to 19-CFM at 125-PSI, very efficient at
higher pressure. The larger capacity compressors also come with
larger air tanks, and you can cram a lot of air into a larger tank at
higher pressure.
Barney Gaylord
1958 MGA with an attitude
http://MGAguru.com
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