Quiet, high-CFM compressor suggestions

[Dan Hintz]

Right now I'm running a 33-gal. Craftsman piston compressor with my laser. It's loud as sin (no hope of holding a conversation near it unless you're screaming in the other person's ear), it won't support the CFM I eventually want, and it's not rated for continuous use. So, I'm looking for a replacement that solves all three of those issues.

My research has led me to scroll or rotary compressors... they're very quiet (usually around the 62 dBa mark, about as loud as a normal conversation), high CFM (a 5HP unit will get me 15-16 CFM without issue), and they're usually rated for continuous use due to the high efficiency. The problem is the cost... those suckers are pricey, coming in at $3.5k+ for a 5HP unit.

Does anyone have suggestions on a different type of compressor that meets the above requirements for a lower cost, or knows of a decent manufacturer of rotary/scroll types that doesn't want an arm and leg for it?

[Steve Leverich]

Dan, I have a Dev-Air 5 horse (real) 80 gallon piston type compressor that's rated just under 20 CFM @ 150 PSI continuous duty 24/7 - just measured SPL at 82 dBA at 2 feet. Not as quiet as a screw but it was $1700 2 years ago. I've yet to run it out of air, even using harbor freight air tools (some of which are quite thirsty) -

Mine is quiet enough for nearly normal conversation 5 feet away, even at 82 dB. Hope this helps... Steve

Oh, Dev-Air is DeVilbiss' industrial line. Meant to mention that sooner.

[Scott T Smith]

Snap-on makes some extremely quiet conventional compressors. Pricy, but not as expensive as the screw compressors. Great quality too.

[Wes Grass]

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.

[Randal Stevenson]

Snap-on makes some extremely quiet conventional compressors. Pricy, but not as expensive as the screw compressors. Great quality too.

I am pretty sure that they don't make their compressors, but they rebrand them. At least some of the older ones, where Saylor Beal (spelling?) models.

IR has been mentioned, and then their is my favorite industrial compressors, Quincy.
Since your looking at Rotary, I am assuming you are planning on three phase?

[Dan Hintz]

Randal,

Quincy has (so far) failed to get back to me with a quote... :(

I'm looking at 240V, single phase... three phase in the home is just not practical.

I'd like to stay away from piston types, if at all possible, as they are just toooooo loud to work next to (I don't have the option of sticking it in another room). I'll take a look at the IR, though, maybe it's "quiet enough".

[Chris Damm]

Low price and quiet do not go together when discussing compressors. The only scroll type compressors I've seen were 3 phase and meant for commerical applications. My old company installed a 25HP one a few years before I retired to handle the increased demand for compressed air. It was loud but much quieter than the 3 piston copressors that it replaced.

[Dan Hintz]

Chris,

Chicago Pneumatic makes several single-phase, 5HP screws... best price I can find, though, is in the $4k area. I'm hoping for something in the $2k range, but that is just a hope, not an expectation...

[Gary Pennington]

Dan,
A few years ago working for a local small manufacturer I built an enclosure lined with sound absorbing foam that completely housed a 5hp Speedaire piston (read noisy) compressor. The compressor was located in a corner so I only had to build 2 sides. Had baffled inlet and outlet on opposite sides that housed a circulation fan for cooling. It was constructed so that the entire thing could be removed for maintenance access. Worked like a charm, you could stand 3 feet from the compressor and carry on a normal conversation.

Gary

[Callan Campbell]

My vote is for a decent Recip. type compressor, but one better than you're using. You're right about the newer units, and their prices, but don't overlook the following.
A used two stage industrial compressor that is pulleyed to spin from 500 to 800 RPM with a decent newer style intake filter should fit your requirements. While this usually means a 3 HP motor unit since they're run at a slower RPM than hooking the same pump up to a 5HP motor and spinning it faster for more output[and a louder operation], it's not a hard and fast rule. You want something with lots of cast iron, a 1725 RPM motor, and if the filter unit isn't the newer style with its tube baffles to cut down on intake noise, relax, you can always buy one and install it. The valving of the compressor can also add some noise, I think it's interesting how much different pumps make in noise while they're running, but alot of this is due to how baffled the intake filter is, and how well it lowers the suction sounds of the pump. You may need to replace some or all of the valves on a used unit, but if the tank is sound, and the pump does not appear to be pumping oil[worn rings possibly], grab it since they run much quieter and put out more air than the noisy single stage units that are sold all over the place and accepted as the "norm" for what a compressor is supposed to do and sound like.
In other words, until you've actually worked with a true commerical/industrial unit, you don't know what you're missing[besides alot of noise:p]
I DO feel your pain, I put up with a noisy, 3450 RPM single stage Sanborn 5HP unit for years until I got my old Saylor-Beall two stage. I already knew how good a real compressor could be, but never came on a used deal at the right time.
You can also do what the poster who suggested getting a 7.5HP pump and spinning it at the slower 5HP range, which is really what the 3/5HP pumps are all about. It's often the same pump, but the pulley diameter sets the RPM, air output ,and noise level in a compressor package. An enclosure is also a real possibilty, not sure if that's an option for you.

[Steven DeMars]

I would go with a 5HP or 7HP Quincey with a horizontal tank. Mount it outdoors in a low profile but nice enclosure, like a dog house wit a compressor inside. Make the walls removable for service.:)

Steve

[Greg Bender]

Dan,
I second what Steve suggested except for the brand.Nothing against Quincy but I work for IR so I'm partial.We have some rotary units that are variable speed based on demand and you almost have to put your head against it to see if it is running.And that's a 150 hp unit.Look on the Industrial Recovery Services auction page ,find a t-30 and mount it under an enclosed lean-to and you will not have any noise.They last forever.They get older units in the lab all the time and they still kick butt.There are options out there for you for sure.
Greg

[Greg Portland]

If you go with Quincy then be aware that some of the newer ones are made overseas and are meant to compete with the "cheaper" compressors (IR also has "cheap" lines). I believe the QR-25 is the direct competitor with the IR T-30. As Greg B. mentions, you can find these used all over the place and service kits are readily available. However, they are not super-quiet (I would not want them in the same room).

You can also find used rotary compressors for cheap but they tend to be much bigger & 3ph. If you get lucky and find a smaller unit then you could consider swapping out the motor or adding a phase converter.

[Dan Hintz]

Interesting options, guys... but just so we're on the same page, this has to live inside. My workshop is "underground", so to speak, in the basement... there will be no knocking of holes in the cinderblock walls.

At the moment, I'm leaning towards a coolant micro-dispensing system rather than using a cold air gun, removing the need for an expensive compressor. I need to be careful how quickly I fill my available space...

[Joe Jensen]

I had the same request. Years ago my dad passed on a used 5HP screw compressor from a place where he worked and had he know what I was looking for I would own one for less than $300. I've watched Craig's List for a used 5hp screw for years and I've never seen one. I ended up getting an old Quincy and fixing it up. New motor, new relief valves, new pressure control. I have $700 in it, for a compressor that sells new for $3500.

The Quincy turns very slowly, large diameter piston, and only 400 RPM. The pump on mine is designed to use with either a 3HP motor or a 5HP motor. I have a 3HP on it because I don't need more CFM, and it's quieter when turning more slowly.

My Quincy uses their model 325 pump which has an oil pump and pressure lubrication. They sell a lower end series now that has splash lube.

Having said that, I have a friend with a 10HP screw Ingersol Rand and wow, it's quiet.

What duty cycle do you need?

[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 (http://www.eatoncompressor.com/catalog/item/504747/6474775.htm). 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 (http://www.eatoncompressor.com/catalog/item/504747/6474775.htm). 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/catalog/item/504747/206949.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?:confused:
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?:confused:
See post #25...

[Callan Campbell]

See post #25...
Aha, what's a Cold Air Gun? So, maybe you DO need a rotary type compressor.

[Dan Hintz]

CAGs use a vortex effect (Google Ranque-Hilsch vortex) to transform a high-pressure air stream into a cold stream and a hot stream. There are no moving parts, no chemicals, etc., just a stream of air using physics to either heat or cool.

http://upload.wikimedia.org/wikipedia/commons/1/1d/Tube_de_Ranque-Hilsch.png

[Joe Jensen]

One more thought. If you don't need more than 100 psi, a single stage unit will generate more CFM than a 2 stage. Single stage 5HP compressors usually have 2 cylinders, each compressing room air into the tank. 2 stage compressors use on cylinder to compress room air into the second cylinder and the second cylinder compresses again.

I think Quincy has detailed CFM ratings at various pressures. If my memory is right, their single stage at 100 psi delivers about 20% more than a 2 stage at 100 psi given the same motor size.

[Chris Friesen]

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.

I just googled it...interesting device. Have you priced out alternatives? The description I read said it's not particularly efficient and is most useful if electrical cooling isn't available or if there is "waste" pressurized gas available.

If you're running a compressor to run a CAG, maybe a more traditional cooling solution might be cheaper to operate in the long term.

[Tony Perrone]

I have a IR in the shop and is not that badfor noise. But if I don't want to hear the anything I just use my CO2 set up, I have a little one in the shop i can carry around and a huge tank that I use to use to frame houses with I have even set the big tank up to back feed into the compressor lines keeping the shutoff on the compressor off"so it didn't try to fill the tank".