Quiet, high-CFM compressor suggestions

[Joe Jensen]

Do a search on that well know auction site the starts with E for this "US AIR COMPRESSOR 30 cfm Ingersoll Rand Screw 5 HP". Looks like what you need less a tank.

[Dan Hintz]

Joe,

15 CFM continuous at 120+ PSI is (was?) the goal, though I could go with something in the 8CFM area and use a smaller cold air gun.

I'm torn on what to do at the moment, as evidenced by the fact that I haven't purchased either a coolant micro-dispensing system or a compressor... if it were any other toy I would have bought it by now.

[Josiah Bartlett]

I have a 20 year old horizontal 30 gallon Quincy compressor that I got on Craigslist for $200. Its marvelously quiet, not as quiet as a good screw compressor but it is quieter than my Unisaw. It has a big cast iron compressor with a 1725 rpm Baldor motor on it, and an intake silencer that looks like an automotive air cleaner. The loudest thing about it is the belt guard vibrating. Its about as loud as your typical Jet type water pump.

[Joe Jensen]

Joe,

15 CFM continuous at 120+ PSI is (was?) the goal, though I could go with something in the 8CFM area and use a smaller cold air gun.

I'm torn on what to do at the moment, as evidenced by the fact that I haven't purchased either a coolant micro-dispensing system or a compressor... if it were any other toy I would have bought it by now.

Then you need something like 30cfm rated so that the duty cycle is rational. The big ones from Quincy, IR, and others can run continuously, but it's not idea. I think you should at least speak with an industrial supplier who specializes in compressors to see what they recommend size wise.

[Dan Hintz]

Joe,

Plenty of the 5HP units are rated at 15-16 CFM continuous duty. Anything much more than 5HP, though, and the current requirements get too beefy for my taste to run in the home. A 7.5HP unit would probably be the max, and I don't want to see the electric bill after running that for a month.

[Jack Clark]

Dan,

Take a look at the all the different compressors manufactured by Castair, a small company in MN.

http://www.castair.net

I'm considering one of their smaller commercial or garage models for my spray finishing needs. Even after adding in the cost of shipping to California, it's still a pretty good bang for the buck.

Give em a call and ask for Pat Kelly. He's a real straight shooter.

[Stephen Cherry]

I've got a 7.5 HP IR, and it has been a solid machine for a long time. I used to work in the pharma industry, and have seen a range of compressors in operation, and yes the rotary kind are nice. It is amazing how quiet a slow turning reciprocating compressor is though.

As stated, I think that a big compressor pullied down to low speed would meet the requirements just fine. Like a 10 hp size pump turning at half speed. These can be found used.

Another thing that helps is piping in the supply air to the pump- this cuts the noise down a little, and an enclosure would help a lot. As far as duty cycle goes, one thing to remember is that the last thing you want is a pump running at high duty cycle. As well as shorter life, the big drawback is lack of cooling time in the tank. The air needs to cool in the tank so that the water can be separated.

In running sensitive equipment, the importance of drying the air cannot be overstated. Basically, this means cool, then coalesce.

[Rick Lizek]

Three phase is certainly practical in a home. Do the homework. Used to be you could pick up three phase equipment for 10 cents on the dollar. Folks are wiser now but still good deals are around. Some screw compressors are very noisy while some pump units are very quiet.

[William Cummins]

You don't want a screw compressor unless your using air continuously. The are made to turn on and run at least a 8hr shift, most are run 7X24 with out turning them off for other than maintenance. Unless you use air like that you will not like them. Almost NO home users run air like that. I looked into one before I purchased my Quincy QR25, the models I looked at had a minimum run time of 20min, so to run a air tool for a a few min. would require the compressor to run for 20 min. not practical for my use. I'm also sure that if you did short cycle one like that, it would not last as long as it should. The oil needs to come up to operation temperature to keep the moisture out of it. BTW the IR T30 is not in the same class as a QR25 (splash lubed VS full pressure). William....

[Dan Hintz]

William,

The application is a cold air gun which uses 15 CFM at 120+ psi, and it runs for many hours at a time... I think a screw qualifies for such a job.

[Harlan Coverdale]

The other option is a piston compressor a size or two bigger than you need, and then slow it down by either putting a smaller pulley on the motor (maybe not possible), or replacing the motor with a lower RPM version. Not going to be cheap if you have to buy new.

Ingersoll-Rand has at times offered a version of their T-30 series set up this way. Basically, a 7-1/2HP compressor driven by a 5HP motor at a lower RPM.

I went this route with an Eaton compressor. Asian parts assembled in the US, but it's nicely overbuilt. It's a pump intended for a 7.5hp motor, slowed down and running with a true 5hp motor. Makes the "5hp" motors on the Borg compressors look like sewing machine motors. At 73 db, it's not as quiet as a rotary pump, but it's the quietest piston compressor I could find in its class. I've been real pleased with it. I compared specs and prices for a lot of brands, but Eaton won out for me.

[Jeremy Brant]

I went this route with an Eaton compressor. Asian parts assembled in the US, but it's nicely overbuilt. It's a pump intended for a 7.5hp motor, slowed down and running with a true 5hp motor. Makes the "5hp" motors on the Borg compressors look like sewing machine motors. At 73 db, it's not as quiet as a rotary pump, but it's the quietest piston compressor I could find in its class. I've been real pleased with it. I compared specs and prices for a lot of brands, but Eaton won out for me.

I've had a similar Eaton for about a year now...this one: http://www.eatoncompressor.com/catal...747/206949.htm. It's held up very well, including a couple accidental overnight continuous runs when I had issues with the sight glass blowing out on the filter/regulator. A friend of mine just purchased the 7.5 hp 80 gal one and has been using it heavy with his blast cabinet. I went from a small oilfree to that one and it's MUCH quieter. I also just recently bought a small oiled Makita (MAC700), and it's super quiet as well, but won't supply the air that you're looking for. I bought that for running nailers and it's perfect for my use.

[Callan Campbell]

Joe,

Plenty of the 5HP units are rated at 15-16 CFM continuous duty. Anything much more than 5HP, though, and the current requirements get too beefy for my taste to run in the home. A 7.5HP unit would probably be the max, and I don't want to see the electric bill after running that for a month.

Remember that to get that air rating out of the pumps, they're spun faster than with a 3HP motor running them ,so you get more noise as a result. The noise level on a decent unit doesn't bother me, but I'm also not standing next to one in a shop setting. We have a 5HP Quincy unit that is run on regular oil, not synthetic, and it's about as noisy as the ancient Wayne Pump compressor that it replaced. Most of the new units are using synthetic oil to get that continous duty rating, so please keep this in mind with your operating costs of owning one. The standard heavy duty rating was 80/20 in the past as far as duty cycles go.
You're trying to balance cost of ownership, noise level of operation, and air output. If you don't need a full 15CFM at 120 psi, then a decent 3HP two stage compressor which is spinning slower and quieter might just work for you. Otherwise, get a full rated 5HP unit and enclose it for lowering the noise of the unit as others have suggested. This way you don't need the extra wiring requirements of going to a big 7.5HP unit, and its greater thirst for power. Our 5HP Quincy runs our whole shop, 7 techs with various air tools going at different times, 2 tire machines, and the air safety locks on some of the service racks along with 2 oil dispensing pumps operating our bulk oil tanks. Surely your air needs are lower than that?
We have a 3HP Champion as a back-up unit in case the Quincy can't handle the load, it's never come on once since the Quincy was installed 2 years ago. I have to run it seperately as a test from time to time to make sure it's still working right in case things go wrong with the "big blue machine" of the Quincy.

[Dan Hintz]

Surely your air needs are lower than that?

See post #25...

[Callan Campbell]

See post #25...

Aha, what's a Cold Air Gun? So, maybe you DO need a rotary type compressor.