Single Stage vs Two Stage

[CompressorPros.com]

Hey guys...most of you know this stuff already, but I decide to make a page with a basic breakdown of the difference is between single and two stage air compressors. Comments are welcome...

Single vs Two Stage

 

[Milton Shaw]

Working pressure of the system is the difference. Most single stage units top out at 125 psi. Most two stage run at 175 psi. Most two stages are heaver tanks, pumps and controls also. Much more of an industrial or professional unit. If all you are doing is airing up tires and single stage will work fine.

 

[Alchymist]

Working pressure of the system is the difference. Most single stage units top out at 125 psi. Most two stage run at 175 psi. Most two stages are heaver tanks, pumps and controls also. Much more of an industrial or professional unit. If all you are doing is airing up tires and single stage will work fine.

And, single stage = $$, two stage = $$$$.

 

[Jim Johnstone]

Now how about this 4 stage compressor I have? [emoji12]

 

[Citation]

I don't see anything about efficiency. I believe one of the advantages of two stage compressors is they save on your electric bill. That might not mater to the occasional shop user but could mater to those who use a lot of air or want higher pressure.

 

[CompressorPros.com]

There definitely would be potential for energy savings, which some of that can be by having the properly sized air compressor. If three phase power is available, that also will help.

 

[tarbellb]

Wow, thanks for the easy, quick, and informative info. That explained it nicely.

 

[justanengineer]

My only critique of your article is that you imply all two-stages use an intercooler between stages which IME isn't true by any means, many industrial units use the compressor oil itself for cooling and/or have an aftercooler.

The only real advantage of a two-stage is to get higher working pressures which in a hobby garage I would suggest is somewhat pointless. The important consideration is flow (cfm), not pressure (psi), which is a factor of both your pump's flow capability and its duty cycle. Many of the cheap box-store units that I've seen have funny and/or low duty cycles, so the choice between cheapie two-stage and professional single-stage comes down to a bit of simple math, not any typically bad rules of thumb. Personally, I'd rather have my lil single-stage Quincy making its 12 cfm continuously than some of the cheapie two-stage box-store brands I've seen making 15 cfm 70% of the time simply bc its more air. Its also typically more efficient using a single-stage as you're generating less heat/wasted energy.

 

[md21722]

My only critique of your article is that you imply all two-stages use an intercooler between stages which IME isn't true by any means, many industrial units use the compressor oil itself for cooling and/or have an aftercooler.

The only real advantage of a two-stage is to get higher working pressures which in a hobby garage I would suggest is somewhat pointless. The important consideration is flow (cfm), not pressure (psi), which is a factor of both your pump's flow capability and its duty cycle. Many of the cheap box-store units that I've seen have funny and/or low duty cycles, so the choice between cheapie two-stage and professional single-stage comes down to a bit of simple math, not any typically bad rules of thumb. Personally, I'd rather have my lil single-stage Quincy making its 12 cfm continuously than some of the cheapie two-stage box-store brands I've seen making 15 cfm 70% of the time simply bc its more air. Its also typically more efficient using a single-stage as you're generating less heat/wasted energy.

Whether or not its pointless depends on what you're doing. Consider some basic air tools like impacts & air ratchets that typically consume large volumes of air for relatively short periods of time. My Snappy's are rated at 37 SCFM and unless I set the regulator to 115 PSI they won't see 90 PSI even on a 25 foot 3/8" hose with high flow fittings. Most single stage compressors have a cut in around 90 and cut out around 125 meaning the air tools never get the air pressure they need for rated performance. And if single stage compressors are "turned up" they tend to run hot and it takes them a while to get up to that high pressure because their performance drops significantly after 110 PSI or so. A dual stage offers more linear performance all the way through their rated pressure band. Dual stage compressors often run cooler (less water) & come with the bells and whistles like after coolers that take even more water out of the line. Per HP, dual stage compressors produce cooler air with less water (more usable air if you will) than a single stage. Remember, air compressors are rated based on CFM of intake air. Cooler, drier air in the tank from a dual stage is more usable than hot, wet air from a single stage.

 

[CompressorPros.com]

Thank for your comments, guys, understand that this is simply a basic explanation and that manufacturers vary in how they build their pumps. A 23 CFM Jenny single stage air compressor can be a much better fit for someone than a 15 CFM BelAire two stage. Your gain with a two stage, is mostly higher pressure, but they also tend to be larger, thus producing more CFM also. We don't sell them, but there are single stage air compressors with multiple pistons that produce extremely high CFM, but at a lower pressure.

 

[larryq]

Thanks for the write-up, a nice summary for those shopping.

 

[CompressorPros.com]

If you get a chance, check out the rotary vs piston page and the sizing a compressor page. Trying to have relevant info available.

 

[Schurkey]

Looked at the "Sizing a Compressor" page. I'd disagree with the chart showing many air tools needing "70 to 90" psi. Of the tools I've used, none of them work worth a **** at less than 90 psi. For example, running impact wrenches at low pressure is hard on the tool, they'll rattle a fastener for thirty seconds before spinning them off, while higher pressure may mean they rattle for two seconds before spinning the fastener off.

I'd like to see an emphasis on air tool "industry standard" 90 psi input pressure WHILE THE TOOL IS RUNNING. 90 psi "in the tank" is entirely insufficient.

I'd also add that quick-couplings seem to kill air flow, and that restriction means a drop in pressure downstream from the coupler.

This is another guide to air compressors:
http://www.ebay.com/gds/Air-compressors-electric-for-home-shops-A-primer-/10000000002309894/g.html

 

[pcmeiners]

"I don't see anything about efficiency. I believe one of the advantages of two stage compressors is they save on your electric bill"

Agree, single stage has a higher output temp, air, and the moisture within the air are expanded more then with a 2 stage compressor..so with a single stage your wasting electric power.

 

[kkroger]

I was not able to find a two stage in my price range that could keep up with my new single stage...
7.5 HP, Single Stage pump, 80 Gallon Receiver, 30CFM at 100 PSI, MAX pressure 150PSI...
Can run my entire shop and will cycle on and off happily...

Would L-O-V-E to have a rotary screw compressor, perhaps some day!

 

[CompressorPros.com]

That's quite the compressor...30 CFM @ 100psi is more than most 7.5 HP two stage compressors.

 

[Packard V8]

It's always "horses for courses." Is the need for higher CFM or higher PSI?

I'd disagree with the chart showing many air tools needing "70 to 90" psi. Of the tools I've used, none of them work worth a **** at less than 90 psi. For example, running impact wrenches at low pressure is hard on the tool, they'll rattle a fastener for thirty seconds before spinning them off, while higher pressure may mean they rattle for two seconds before spinning the fastener off.

I'd like to see an emphasis on air tool "industry standard" 90 psi input pressure WHILE THE TOOL IS RUNNING. 90 psi "in the tank" is entirely insufficient.

I'd also add that quick-couplings seem to kill air flow, and that restriction means a drop in pressure downstream from the coupler.

Agree. If one wants an education, plumb in a pressure gauge at the tool (at the end of however many feet of 3/8" or 1/4" hose and QD fittings, then stand beside the tank and pull the trigger and compare the end gauge with the tank gauge. I've seen 175 PSI at the tank and 75 PSI at a tool at the end of 150' of 1/4" hose. Who'd do such a stupid thing? Many, many shops.

FWIW, I recently bought a 5hp compressor from a cabinet shop going out of business which was plumbed just that way. They wore out the first compressor and then used the tank as additional volume, when what they really needed was larger diameter supply lines all over the shop. The largest piece I saw while disassembling was several feet of 3/8" pipe and I got more 1/4" hose than I'd ever have a use for.

On an industrial setup, supply lines of 1" to 2" black pipe, with a 1/2" drop hose only a few feet long and high volume QD fittings and 90 PSI at the tool is usually enough.

FWIW, a true 150-175# at the tool will wear it out quickly and make it very difficult to control.

jack vines

 

[sberry]

Where the loss is at is in pumping 150 single stage, at 100 the pump is working pretty well. 2 stage is for running air tools really, The headroom allows for steady pressure delivery to a regulator and it generally cuts in before there is loss of performance at the tool. It allows it to be turned up some to make up for line losses on the secondary hoses and fittings.
A single needs to be fully pumped for full power while a 2 may be able to use all of the cycle till kick on.

 

[sberry]

It's always "horses for courses." Is the need for higher CFM or higher PSI?



Agree. If one wants an education, plumb in a pressure gauge at the tool (at the end of however many feet of 3/8" or 1/4" hose and QD fittings, then stand beside the tank and pull the trigger and compare the end gauge with the tank gauge. I've seen 175 PSI at the tank and 75 PSI at a tool at the end of 150' of 1/4" hose. Who'd do such a stupid thing? Many, many shops.

FWIW, I recently bought a 5hp compressor from a cabinet shop going out of business which was plumbed just that way. They wore out the first compressor and then used the tank as additional volume, when what they really needed was larger diameter supply lines all over the shop. The largest piece I saw while disassembling was several feet of 3/8" pipe and I got more 1/4" hose than I'd ever have a use for.

On an industrial setup, supply lines of 1" to 2" black pipe, with a 1/2" drop hose only a few feet long and high volume QD fittings and 90 PSI at the tool is usually enough.

FWIW, a true 150-175# at the tool will wear it out quickly and make it very difficult to control.

jack vines

If a little is good a lot must be better? 1/4 hose is substandard, 3/8 is adequate and the most practical and common for this small shop hand tool air work. I have some 1/2 on a main or 100 ft run on 2 stage to a hose reel with 50 ft of 3/8. I do have some big fittings and some 1/2 hose and I run in to the occasional pinch for a 3/4 gun and can hook to a sand pot but I have a lot of stuff not normally found in a hobby garage.
A simple trick to get a short boost is to bypass a 50 ft with a 25 and can use matching equipment.
On a zippy 1/2 air gun needing absolute max output this would provide real net savings where changing from 1/2 pipe to 3/4 at 100 ft on the main would net nothing or maybe .3 vs 8#or more especially thru only 1 connector.

 

[sberry]

In my shop the end user never moves a section of hose, its either a dropped whip or on a hose reel and they make the connection at the tool.

 

[justanengineer]

Whether or not its pointless depends on what you're doing. Consider some basic air tools like impacts & air ratchets that typically consume large volumes of air for relatively short periods of time. My Snappy's are rated at 37 SCFM and unless I set the regulator to 115 PSI they won't see 90 PSI even on a 25 foot 3/8" hose with high flow fittings. Most single stage compressors have a cut in around 90 and cut out around 125 meaning the air tools never get the air pressure they need for rated performance. And if single stage compressors are "turned up" they tend to run hot and it takes them a while to get up to that high pressure because their performance drops significantly after 110 PSI or so. A dual stage offers more linear performance all the way through their rated pressure band. Dual stage compressors often run cooler (less water) & come with the bells and whistles like after coolers that take even more water out of the line. Per HP, dual stage compressors produce cooler air with less water (more usable air if you will) than a single stage. Remember, air compressors are rated based on CFM of intake air. Cooler, drier air in the tank from a dual stage is more usable than hot, wet air from a single stage.

Youre having a very common issue bc youre running too small of a hose, at those rates you should be running 1/2" or larger else youre going to get that massive pressure drop. I dont care much for rules of thumb, but one we use at work on these small sizes is 5 psi drop/50' of line.

Quite realistically the argument is pretty pointless bc in reality many folks use single-stage compressors well within their design spec daily and dont have the issues mentioned. No, most arent turning anything up or abusing anything, most quality single-stages will run up to 150 psi. Personally I've never had issues running my old 3/4" CP impact and have even run the pressure pot for short periods with my lil Quincy. As for air temps youre backwards, temperature correlates to pressure --> two-stages heat the air more and with either an intercooler or aftercooler most two-stage air temps are still higher than single stage temps. In reality its a tradeoff, if you need the higher pressure (most dont), then you have to pay to play.

 

[boosteddsm92]

A 23 CFM Jenny single stage air compressor can be a much better fit for someone than a 15 CFM BelAire two stage.

I have that same Jenny but w/a 60 gallon tank, J5A-60V. I love it. The CFM seems to be so much higher than most other comparable compressors. Any idea why this is? I also don't get why no one seems to like or recommend the Jenny compressors? They make a great USA made compressor.

 

[kkroger]

That's quite the compressor...30 CFM @ 100psi is more than most 7.5 HP two stage compressors.

Exactly! But the pump is about as big if not bigger than a Harley Big Twin!
I have seriously thought about polishing up the edges of the fins and putting an S&S Super E/G Air Cleaner on it for fun....

It is an Eagle, same company as Max Air, 7180V1MS, same model no for the MaxAir version.

Blue instead of Yellow. Local Store had it on the sales floor, so I was able to pick it up as it were. Was interesting to UNLOAD...

 

[md21722]

I have that same Jenny but w/a 60 gallon tank, J5A-60V. I love it. The CFM seems to be so much higher than most other comparable compressors. Any idea why this is? I also don't get why no one seems to like or recommend the Jenny compressors? They make a great USA made compressor.

Lots of folks like Jenny compressors. As far as I know they are most common in contractor circles where they are used to power nailers, etc and may either be electric or gas powered. They are also used for climate control & sprinkler systems. Different markets gravitate towards different brands.

 

[mikegt4]

I have a Emglo (now sold as Jenny) compressor. They make an excellent product.

 

[CompressorPros.com]

Jenny makes great compressors...and in the USA. They were one of the first lines we carried because of their quality.

 

[Dick in Wisconsin]

My need for a compressor is pretty modest. I don't do body work and don't use many air tools. I have a small single stage compressor I got $75 that won't build pressure I will look at this winter.

I do however need high pressure. The tires in the motorhome should be taken to 110psi. I don't know if this modest compressor will get the job done, I'm concerned it won't.

Are there available small two stage compressors that could give my 150 to 175 psi in a smaller package than 80 gallons and hence a smaller price than $1,000? Maybe three horse? I have access to 240 volts of single phase power.

 

[CompressorPros.com]

To get the 150+ psi, you'll need a two stage. BelAire's 216V and Chicago Pneumatic's RCP-561VNS are pretty popular since they fit that exact need. 60 gallon, 15.3 CFM and a max pressure of 165 psi. Since you are in WI, if you want one of these, use Coupon Code: $40ON60V to save $40. We have to pay tax in some states, but not in WI.

Both of these have a two year warranty that cover the whole compressor package.

 

[CompressorPros.com]

That deal is good in the following states: AL, AR, AZ, CO, CT, DE, FL, A, IA, ID, KS, KY, ME, MI, MN, MO, MT, NC, ND, NE, NJ, NM, NV, OH, OK, RI, SC, SD, TN, TX, UT, VA, VT, WA, WI, WV, WY

 

[Infinia]

Youre having a very common issue bc youre running too small of a hose, at those rates you should be running 1/2" or larger else youre going to get that massive pressure drop. I dont care much for rules of thumb, but one we use at work on these small sizes is 5 psi drop/50' of line.

Sorry most reasonable folks choose 3/8" line, 1/2 is costly and plain bastid to drag around. Quoting only 5 psi losses on 1/2" is plain useless without knowing 1) length of line, 2) tool CFM, 3) pressure , AND knowing something about their relationship to line pressure losses /tolerances. Calling for 1/2" line w/o knowing anything else, is a rule of thumb, a dumb one. Having> 150 psi compressors allow for lots more line losses, full stop>.

Quite realistically the argument is pretty pointless bc in reality many folks use single-stage compressors well within their design spec daily and dont have the issues mentioned.

hmm that is entirely the whole point, I see many problems reported here at least once a week about compressors set for 90 psi cut-in, (please note this setting has zero margin for a high CFM tool spec'd @ 90, so you and others wrongly advising them to use a 1/2" hose with industrial fittings just don't fly right!!) If folks would just get a 150 psi comp. with the biggest motor/pump combination they could tolerate / afford and /or pay lesser attention to the larger tanks we'd have way less folks in trouble. Instead they buy large tanks at 125 psi thinking they are good to go.

 

[Roberts210]

I've bought (and sold) a variety of used 20-gal compressors over the years and one observation I've made is not too many people bother to use real compressor oil in their compressors. I've seen the results of long-term use of auto motor oil--crud all over the valves and heads. Right now I'm running a Speedaire 20-gallon unit and I love it. But the first thing I did when I got it was change the oil and put compressor oil in it.

 

[sberry]

I don't see anything about efficiency. I believe one of the advantages of two stage compressors is they save on your electric bill. That might not mater to the occasional shop user but could mater to those who use a lot of air or want higher pressure.

I will agree about hi pressure but am always curious as to what "a lot of air " is?

Quite realistically the argument is pretty pointless bc in reality many folks use single-stage compressors well within their design spec daily and dont have the issues mentioned.

Page after page day after day of someone trying to wring every drop out from a **** comp. The solution, another bandaid, get a bigger hose again.
3rd, the electric savings to those on this forum about power savings are moot. None of this is efficient anyway and that's not why air is used, its to get work done.
This is exactly why they have the 3 hp mechanics comp back in the day. Exactly this scenario.

 

[sberry]

No, most arent turning anything up or abusing anything, most quality single-stages will run up to 150 psi. Personally I've never had issues running my old 3/4" CP impact and have even run the pressure pot for short periods with my lil Quincy.

I will agree that some knob running a cabinet shop with 1/4 lines is going to have a problem on larger tools, this is pretty obvious but you do make a point here. I am going to counter one of perspective.
e a long time to make air demand a reflex of sorts with sizing and rules of thumkb are fine here as none of the math is exact and when it is we got someone pushing a pencil likely doesn't have the personal experience. Almost all engineers are smarter than I am so this isn't much of an issue but I done this about every way it can be more than once. I see a lot of people with their own ideas about it, some good, some bad and some don't matter much. Everytime someone mentions sandblast out come the amateur pipe sizers with their "rule of thumb" they mostly don't have a clue about and obviously very little real experience. This isn't a stab at anyone but is kind of rudimentary at best, its not dangerous, just not very accurate.
Many of the calcs are misunderstood. (not every circuit with a 20A breaker needs to be calc for 20A voltage drop at 100 ft. ) Same for a pipe, if its good for 50 at 100 what makes one think they need to upsize it at 25 ft for their 5 hp comp? What makes one think they use a lot of air or electric more than other people?
Reason I know some of this is I have the same stuff doing the same work, while I can do it 100 ft 1/2 they seem to think they will have trouble with 1/2 the load and work requiring 3/4 at 25? Its just something in the human mind cant help itself, the fear of loss is so high it drowns out any real accuracy with estimation or calculation.

 

[Qualitytools]

Hey guys...most of you know this stuff already, but I decide to make a page with a basic breakdown of the difference is between single and two stage air compressors. Comments are welcome...

Single vs Two Stage

I tried your link and it's broken nothing there

 

[Z2V]

Worked for me

 

[joel63]

https://www.compressorpros.com/sizing-guide/

 

[The Tool Tyrant]

Re: Single Stage vs Two Stage vs Motor Cycling Frequency

The one factor that seems to be overlooked so far in this discussion between single and two stage pumps, is drive motor cycling frequency. Being as a two stage pump is placing more cubic feet (greater volume) of air into the receiver than a single stage, (175 psi vs 125 psi...typical) and if in both scenarios, the regulators were set at the same work pressure, the single stage pump will have to cycle with much greater frequency than the two stage.
The greatest wear an electric motor sees, is in starting...not continuous running and this is even worse in single phase motors vs. 3 phase as starting capacitors also need to be factored in.
My shop compressor is a Quincy QR325 pump with aftercooler, driven by a 5 hp Baldor (1725 rpm) motor, sitting on a 120 gal receiver with a 240 gal. reserve receiver placed next to it. both receivers have Bekomat zero-loss condensate drains. This compressor takes care of 5 of us in the shop, along with two CNC machines. With 360 gallons of air storage, the compressor only averages 4-5 cycle periods a day (10 hr. work day) Of course it runs for 6-8 minutes to go from 145 to 175 cut-off, but the pump is designed to run 7-24, so I know that this combination is the best case scenario for motor longevity.

Just something else to consider!

Tom

 

[CompressorPros.com]

Typically, two stage air compressor pumps are larger, and make more volume (CFM) so they would definitely cycle less in the same application. There are, however, higher volume single stage pumps for applications where more CFM is needed without the higher psi available from a two stage.

 

[The Tool Tyrant]

Typically, two stage air compressor pumps are larger, and make more volume (CFM) so they would definitely cycle less in the same application. There are, however, higher volume single stage pumps for applications where more CFM is needed without the higher psi available from a two stage.

Yes, and I concur. Along that same line, I'm not sure that some folks realize that a 2 cylinder single stage pump, with each cylinder having the same displacement as the low pressure cylinder of a given two stage pump, would DISPLACE twice the CFM as the two stage at matching rpm. Of course as receiver pressure increases, the curve changes in favor of the two stage. Fun stuff!

Tom

 

[srr]

I've had every version of air compressor and I'm firmly in the "two stage" 80 gallon camp. I have my compressor dialed down to a 90-120 PSI cycle. I have a 30' 1" copper manifold with a 50' hose reel on each end. The beauty of having "overkill" on the compressor is the ability to crank it up if the need would arise. I would rather have a machine hardly working than straining to keep up.