Smokin Joe

Why are two stage compressors so expensive, what are they doing for me? Is it really necessary?

I've seen 1 stage 60 gallon compressors go for $400.
I can't find a 2 stage 60 gallon compressor for under a thousand.

Larry B.

A two stage is better for commercial use because it usually is a little higher pressure at a lot more CFM (cubic feet per minute) that means several people can use the air at one time and the compressoor will keep up. A single stage is all a home mech needs. BTW when choosing a compressor the MAIN factor for comparison is CFM not how big the tank is. I bought a 60 gal. from Sam's 15 years ago and it is still doing great.


[Modified by Larry B., 1:31 AM 7/5/2004]

LAvetteman

A 2 stage compressor basically can pump twice the air a similar single compressor can in a given amount of time. Which in most jobs is not important, but if you are using an air sander or painting a vehicle your single stage may or may not be able to handle the extreme duty. Most compressor manufacturers recommend that you don't allow the compressor to run more than 50% of the hour total. Constant starting and stopping isn't good either.

Here is my take on that though. When I painted my 71 I had a brand new 80 gallon, 7 hp, 2 stage compressor($1200) sent to my house for the job. I barely got through shooting the primer and the motor failed (start capacitor went out). Luckily I had a 15 gallon 10 year old compressor on stand by. I connected the two compressors together so the 15 gallon would run long cycles to keep the 80 gallon tank full. I finished the primer and shot the base and the clear with the air that 15 gallon compressor pumped with no problem.

As mentioned above the size of the tank is most important. IMO the next thing is make sure it is a seperate component unit (the pump and motor are not as one) so that you can upgrade the compressor and the motor when the time comes.

Chuck Gongloff

If you ever plan to run a glass beader, or do sand blasting, you need LOTS of CFM. You should consider a 2 stage compressor. For intermittant air tool use, painting, etc., a single stage will be fine.

I have a 5 HP two stage 80 gallon "Industrial Air" compressor. LOVE it. Chuck

mrvette

That 5 hp 80 gal commercial type unit I had up north was a really nice unit, had to admit.....but kinda needlessly expensive to operate, I thought.....

this 3 horse 30 gal unit here is fine for most anything I"m doing....

OH, get the type with a drive belt, they bee noisey ok, BUT that those so called oil less reed type things, a buddy has one of those, and they make the GOD DAMNDEST NOISE, I can't stay in the garage when it takes off...wakes up the dead indians under the house foundation....

GENE

Mako72

After suffering with a 20 gal compressor (ran the poor thing to death) I bought a larger unit. It's a 2-stage, 80 gal unit and puts out serious CFM. It helped that I got a great deal on it as HQ was going out of business. I later built a homemade sand blast cabinet and now I have the compressor that can support it. I would err on the larger size. You never know what you will want to be doing down the road. Charles

zwede

I've been reading up on compressors as I'm in the market for one.

Direct drive pros: Oil-less. No Maintenance.
Direct drive cons: Short life. Noisy.

Belt drive pros: Long life. Quiter than direct drive.
Belt drive cons: Requires oil and filter changes.

Then there's the new "invector" compressor from Coleman. It seems interesting. It's basically an improved direct drive. By using a universal rather than inductive motor they have halved the startup-current. They use the air being sucked into the pump to cool the motor and pump so the life expectency is increased compared to direct drive. An intake muffler makes it much quiter than a direct drive. Not sure if it is quiter than belt drive. The invector is still maintenance free like direct drive. It seems like a good choice for hobby use. The largest model is 27 gallon tank and 4 CFM @90 PSI, 6 CFM @ 40 PSI. Not a good choice for a serious shop, but I think it should do ok for those of us that don't use it everyday. Best part is the price, only $249. I figure I'll give it a shot and if it dies within the first year I'll get it fixed under warranty and then I can put it on ebay and get a belt-drive.

MikeC

The reason to go to a two stage compressor is because they more efficiently compress air. The first stage compresses it to a pressure then it is cooled off and then it compresses the air to the final pressure, then cooles it off again.

Much of what was said was only partially correct.

They do not compress twice as much air... That is a twin cylinder air compressor... which is totally different from a 2 stage.

They tend to have more output(CFM) because at smaller output the cost cannot be justified to go to the more efficient 2 stage.

AS for the pressure, that is the design of the compressor some 2 stage compressors run 125 some 150, some 175 + PSI it depends on what job the job compressor is designed for. The problem with running higher pressure systems is you have to remove more heat from the system than a lower pressure system

Smokin Joe

Thanks guys.

I am thinking of getting a higher volume (60+ gal) single stage. I just cannot justify the greater cost of the two stage, even though I am going to do most to all of the blasting of the car. I probably will not need to bead blast the frame the car has been garraged for 20 years and doesn't have severe rust anywhere. Very solid car, and my dad is the original owner. I'll probably keep the tank and sell the bead blaster when finished.
Thanks.
Anymore comments are always welcome, this purchase is a week away.

norvalwilhelm

I agree with Mike. The 2 stage compressor uses one large cylinder for the first compression, then dumps this in the second smaller cylinder where the air is further compressed. This costs volumn. It doesn't increase volumn.
Why do you need 175 psi for anything. Impact guns are not rated for this pressure.
You need volume. My single stage puts out 18 cfm at 125 psi pressure. More then enough for any job.

MikeC

Spy, I sand blasted my entire frame with my little 25 gallon direct drive piece of crap compressor... it ran constantly but it did the job. I also sprayed the frame and put the primer sealer on the car with it. It did great on that with the HVLP gun I bought it barely runs.

The great thing about direct drive compressors is they are cheap to rebuild($40 CA).... the problem is they are noisy, they create extremely hot air since they have no aftercooler.

A nice 60-80gal 5-7hp single/ dual piston, single stage compressor will be more than you ever need.