In my opinion it is "the amount of energy you can store in the tank".
A single stage will usually have a tank pressure of 125-130 and a
dual stage is usually around 175. So you are able to store more
energy in the tank and therefore draw more energy from the tank
before the compressor comes on and/or you draw it down lower
than what your tools need.
I know that my dual stage will be at 175, when I use it will draw down
to about 155 before the compressor comes on, the compressor is
capable of keeping up with any of my tools so the tank never seems
to go below 135 about, and I have the regulator off the tank set at 125
so the airlines in the garage never go below 125.
I speculate that a single stage would start at 130, draw down to 115
or so and then the compressor would come on and like the dual stage
would need to keep up with the air the tool is drawing from the tank.
The one you are talking about can probably keep up, so the difference
would only be that the single stage is much closer to the lower limit than
the dual stage would be.
As a side note, the 805rpm is a nice feature, especially compared to the
buzz-box racket of the direct drive compressor.
Arvid
> Howdy,
>
> Whats the deal with single vs. dual stage compressors?
>
> I've long been thinking that I'd want to get a decent 60 or 80 gallon two
> stage compressor when I upgrade next. But I was reading the recent TP
> Tools thanksgiving sale flyer and they had some listings for High output
> single stage compressors.
>
> One in particular was $650 and has a working pressure of 95-125 psi, with
> 16.5 cfm @ 90 psi (Eagle brand three cylinder 5 hp running, 23A at 230VAC,
> 7hp peak, 60 gallon). No spec on pump rpm.
>
> That's as compared to $1300 for a Champion 5hp two stage, @19.1 cfm @125
> psi, 22A @230vac. The pump rpm on this one is 805rpm
>
> I realize that 19.1 cfm @ 125psi is more air that 16.5 cfm @ 90 psi, but
> would I ever care about that? I'm going to be a single user using normal
> air tools like cut offs & body sanders, plus a blast cabinet, perhaps
> painting a car, etc.
>
> Currently I have a Craftsman direct drive single stage that says it does 7
> scfm @ 90psi... That thing won't keep up with a cutoff very long.
>
> Half price is pretty attractive if it'll do what I need it to do...
>
> Mark
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