Two Stage

The seven kinds of two-stage units on this page

Stationary electric simplex (one pump, one motor)

The bulk of the category. Typically 5, 7.5 or 10 HP on an 80- or 120-gallon ASME tank, vertical or horizontal, with a start/stop pressure switch, fully enclosed belt guard, cast iron cylinders and an oil sight glass. Examples: BelAire 318VN, 338VLE, 6312VE; Chicago Pneumatic RCP-583V, RCP-7583H, RCP-C10123V; EMAX EI05V080I1, ESP10V120V1.

Duplex (two pumps and two motors on one tank)

23 of the 146 models are duplex. They pair two pumps and motors with an alternator so the load is shared. BelAire's duplex listing states the line runs up to 20 HP and delivers up to 50.50 ACFM on single-phase power. Chicago Pneumatic's Iron Series duplex adds a control panel offering alternating or isolated operation, a delayed start to lower amp draw, and a second pump/motor that starts automatically if one side runs for 5 minutes. Duplex is the answer when you need 10 HP of output but only have single-phase service: the RCP-C10121D is 10 HP (2 x 5 HP) on 208-230/1.

Sound-attenuated cabinet models

Eight models are enclosed. Chicago Pneumatic's Quiet Performance units publish sound levels: 66 dBA on the 5 HP RCP-581VQP and RCP-583VQP, 69 dBA on the 7.5 HP RCP-7581VQP and RCP-7583VQP. BelAire's QP338VLE also lists 69 dBA. The BelAire QP series adds low oil level protection, an automatic tank drain, a magnetic starter and high-temperature shutdown, and its listing describes it as a piston compressor with the noise level of a rotary screw, intended for installation inside the work area. Cabinets cost you height and width: 39 x 25 x 80 in. on the BelAire QPs, 38.2 x 24.3 x 80 in. on the CP QPs.

EMAX Silent Air intake silencer

Thirteen EMAX models are listed with the Silent Air intake silencer, which routes intake air through baffle plates and pre-filter media; ten of them also publish the "Silent Air: Y" spec row. EMAX states the whisper series reduces stationary compressor dBA ratings by as much as 25 percent, and that the low-profile system adds four levels of air filtration.

Gas-engine truck-mount units

Eight models run on a gasoline engine instead of a motor, for service trucks and job sites with no power. BelAire 3G3HHL (13 HP Honda) and 3G3HKL (14 HP Kohler) put 25.3 CFM at 100 PSI on a 30-gallon horizontal ASME tank with a 3/4 in. air outlet, 45 x 19 x 45 in., 378 and 369 lbs. The 4G3HHL and 4G3HKL are the same footprint at 23 CFM at 100 PSI. EMAX goes larger: the EGES1830ST and EGES1860ST use a Honda GX630 at 18 running HP, 34 CFM at 110 PSI, 800 RPM pump, 3200 RPM engine, 5-gallon fuel tank, on a 30- or 60-gallon tank; the EGES2460ST is 24 HP with 58 CFM on 60 gallons. EMAX notes its gas units need a 12-volt battery and two battery cables to be truck-ready.

Three-in-one air, generator and welder

One unit, the EMAX EGES14020T, combines a 14 HP Kohler Command engine with electric start, a two-stage cast iron pressure-lubricated pump (19 CFM, 17 CFM at max PSI, 175 PSI), a 5,000 W continuous / 6,000 W surge generator with two 120 V 20 A outlets and one 240 V outlet, and a DC 190 A stick welder. Air storage is two ASME tanks totaling 20 gallons; the wheelbarrow tires can be removed to make it stationary.

Bare pumps

Three EMAX pumps are sold without tank or motor for rebuilds and custom skids: APP2I0524TP (5 HP, 800 RPM, 245 lbs., 10-1/4 in. x 5-3/8 in. bolt pattern), APP4V1043TP (10 HP, 800 RPM, 287 lbs.) and APP4V2598TP (25 HP, four-cylinder, 98 CFM displacement, 93 CFM at 100 PSI, 89 SCFM at 175 PSI, 800 RPM with a 550 RPM minimum, counter-clockwise rotation). All three are rated up to 70,000 hours on B-10 bearing life.

How much CFM you actually get

Horsepower is a poor proxy; the pump decides. Across this category:

• 5 HP: 16.1 to 19 CFM at 100 PSI. BelAire 4916V 16.1, BelAire 418V and CP RCP-C583V 18, CP RCP-583V 18.5, BelAire 318VN 18.6, EMAX EI05V080I1 19. BendPak TSP-580V-601 is rated 17 CFM at 175 PSI.
• 7.5 HP: 23 to 31 CFM at 100 PSI. CP RCP-C7583V and BelAire 438VL 23, BelAire 338VLE and CP RCP-7583V 25.3, EMAX ES07V080V1 31.
• 10 HP: 35 CFM (BelAire 6312V/6312H, CP RCP-C10123H) to 38 CFM (EMAX EI10V080V1, ESP10V120V1).
• Duplex: 36 to 37.2 CFM at 2 x 5 HP, 46 to 50.5 CFM at 2 x 7.5 HP, 70 CFM at 2 x 10 HP.
• Large single-pump: EMAX EP20H120V3 at 82 CFM, EP25H120V3 at 96 CFM, both at 100 PSI.

86 of the 146 listings quote a second flow figure at 175 PSI (or at max PSI). Size against the higher-pressure figure if you run tools near the top of the range: the BelAire 6312D moves 70 CFM at 100 PSI but 64 CFM at 175 PSI. Most Chicago Pneumatic listings quote displacement and flow at 100 PSI only, so on those models size against the 100 PSI figure and confirm the high-pressure number with us.

Space, ceiling and weight

Tank sizes here are 20, 30, 60, 80, 120 and 200 gallons. Footprints repeat by family, so plan around these figures and confirm on the model page:

• 80-gallon vertical: 39 x 24 x 77 in. (BelAire 318/338 series, CP RCP-583V) or 37 x 24 x 72 in. (BelAire 418/438 Iron Series, CP RCP-C583V).
• 80-gallon horizontal: 71 x 24 x 49 in.
• 120-gallon vertical: 42 x 30 x 74 in. EMAX 120-gallon verticals run 44 x 31 x 80 in. uncrated.
• 120-gallon horizontal simplex: 73 x 24 x 49 in. Duplex: 77 x 27 x 56 in., or 81 x 27 x 52 in. at 20 HP.
• 200-gallon horizontal duplex: 85 x 27 x 52 in.

Vertical units are 70 to 80 in. tall: the 60-gallon BelAire 4916V is the short one at 70 in., 80-gallon verticals run 72 to 77 in., and 120-gallon verticals and QP cabinets reach 80 in. Measure door height and any overhead obstruction before choosing vertical over horizontal. Weight runs from 261 lbs. (BelAire 4916V) to 1,636 lbs. (EMAX EP20H120V3 and EP25H120V3, 1,715 and 1,750 lbs. shipping, crated at 48 x 84 x 67 in.); the heaviest Chicago Pneumatic is the RCP-C20203D at 1,525 lbs. The 67 BelAire, 53 Chicago Pneumatic and one BendPak listings are flagged for free shipping; the 25 EMAX listings are not.

Power: phase, voltage and breaker

By listing, 45 models are 208-230 V single phase, 46 are 208-230 V three phase, and 44 are 460 V three phase or tri-voltage; the remaining 11 are gas-engine units and bare pumps. Three-phase cuts the current sharply, which matters when your panel is tight. From the listings:

• 5 HP: CP RCP-C581V draws 25-23 A on 208-230/1 (40 A breaker); RCP-C583V draws 14-13.2 A on 208-230/3 (25 A); RCP-C583V4 draws 6.6 A on 460/3 (15 A).
• 7.5 HP: RCP-C7583V, 18-17.2 A, 30 A breaker; RCP-C7583V4 on 460 V, 8.6 A, 20 A breaker.
• 10 HP: RCP-C10123H, 26-25 A, 60 A breaker; RCP-C10123H4 on 460 V, 12.5 A, 25 A breaker.
• Duplex on single phase pulls hard: RCP-C10121D 50-46 A (60 A breaker), RCP-C15121D 64-58 A (80 A breaker).
• EMAX single-phase 80-gallon units list 40 A (5 HP), 50 A (7.5 HP) and 60 A (10 HP) breakers with 135, 210 and 270 peak starting amps. EP20H120V3 lists 70 A at 208/230 or 35 A at 460 V; EP25H120V3 lists 80 A or 40 A.
• BendPak TSP-580V-601: 24 A draw, 40 A breaker, 208-230 V, 1-phase, 60 Hz, 72 dBA.

Magnetic starters are not universal. BelAire 318VN states no magnetic starter is required; the CP simplex units list a CPXHT-25 starter; BendPak lists Magnetic Starter: No; EMAX EI05V080I1 lists Mag Starter: N while the 7.5 and 10 HP EMAX units list Y. Several three-phase BelAire listings carry a plain warning that the unit MUST have three-phase electric power.

Reading the model numbers

BelAire uses 318 and 418 prefixes for single-phase and 338 and 438 for 208-230 V three-phase, with a trailing 4 for 460 V (338V4, 438VL4, 3312D4). V and H are the tank orientation, L adds horsepower (318VN is 5 HP, 318VL is 7.5 HP) and E marks the Elite build. Chicago Pneumatic follows the same idea: RCP-381 and RCP-581 are single phase, RCP-338 and RCP-583 are three phase, and a trailing 4 is 460 V. In the CP Iron Series, a Premium model such as the RCP-C581V adds a low oil level switch, an automatic tank drain and a belt-guard aftercooler over the standard RCP-C581VS.

What the tanks and units are certified to

Almost every tank listing here is described as ASME code with ASME safety valves; 141 of the 146 listings say so. The three bare pumps ship without a tank, and the BelAire 438VE and 438VE4 listings omit the ASME wording their sister models carry. Chicago Pneumatic's Iron Series states its tanks are both CRN and ASME certified and National Board Registered, with an ASME certified safety valve on tanks and pumps. EMAX electric units list ETL and ASME, and most add CRN; the EP series plus the ESP05V080I3 and the ESP10V120V3 list CSA, ASME and ETL instead. The two EMAX gas units that publish a certifications field, the EGES14020T and the EGES2460ST, list ASME, CRN and EPA. The EGES1830ST and EGES1860ST state only an ASME certified air receiver and ASME approved safety valves; the BelAire gas units publish no certification marks beyond the ASME tank and safety valve noted above. BendPak lists UL, CSA and ASME on the TSP-580V-601, which also carries a California Proposition 65 warning. EMAX states its belt guards are OSHA approved. BelAire QP tanks are described as ASME/CRN. Certification wording is per listing, so confirm on the model page for the exact unit you order.

Comparison: 12 models across the range

Before you order: listing conflicts to confirm

A few manufacturer sheets in this category contradict themselves. Where that happens, the model number and the specification table govern, and it is worth a call to confirm:

• The BelAire 318H listing is titled as a 5 HP unit but prints the 318VL specification block (7.5 HP, 80-gallon vertical).
• The BelAire 418VE carries a boilerplate "MUST Have Three-Phase Electric Power" bullet, while its specification table reads Phase 1 and the 418 prefix is BelAire's single-phase series.
• The EMAX EGES1860ST body text repeats "30-gallon" from the smaller unit; its model name and specification table both state a 60-gallon air tank.
• The EMAX APP4V2598TP opens with a "10HP" headline copied from another pump; the model number and the body describe the 25 HP four-cylinder pump at 93 CFM at 100 PSI.

Frequently asked questions

What is the real difference between single-stage and two-stage?

Pressure and sustained output. Two-stage compression lets these units hold 175 PSI, and 86 of the 146 listings quote a second flow figure at 175 PSI (or at max PSI) so you can see what the machine still delivers under load. Most Chicago Pneumatic listings quote displacement and flow at 100 PSI only, so on those models size against the 100 PSI figure and confirm the high-pressure number with us. A single-stage machine typically tops out lower and loses more flow as pressure climbs.

How do I size the compressor to my shop?

Add the CFM of the tools that will run at the same time, then match against the CFM at 100 PSI figure for the model. In this category that means roughly 16 to 19 CFM from a 5 HP unit, 23 to 31 CFM from 7.5 HP, 35 to 38 CFM from 10 HP, 46 to 50.5 CFM from a 2 x 7.5 HP duplex, and 70 to 96 CFM at the top of the range. Tank gallons buy you recovery time, not flow.

Do I need three-phase power?

No. 45 of the 146 models run on 208-230 V single phase, including 5, 7.5 and 10 HP units and single-phase duplex machines. The trade-off is current: a 5 HP CP Iron Series unit draws 25-23 A on single phase versus 14-13.2 A on three phase, and a 15 HP single-phase duplex is listed at 64-58 A with an 80 A breaker.

Vertical or horizontal tank?

Vertical saves floor area and costs height: an 80-gallon vertical occupies about 39 x 24 in. of floor but stands 72 to 77 in. tall, and enclosed QP cabinets stand 80 in. A horizontal 80-gallon is about 71 x 24 in. on the floor at 49 in. tall, which fits under low ceilings, mezzanines and overhead doors.

Which models work on a service truck?

The eight gas-engine units. The 30-gallon BelAire truck-mount models are 45 x 19 x 45 in. (3G3HHL, 3G3HKL) or 45 x 19 x 43 in. (4G3HHL, 4G3HKL), 369 to 501 lbs.; the EMAX Honda GX630 units add electric start, a 5-gallon fuel tank and 34 CFM at 110 PSI. The EGES14020T adds a 5,000 W generator and a 190 A stick welder on the same frame.

Is a magnetic starter or automatic drain included?

It varies by model, so check the feature list on the unit you want. Several BelAire and Chicago Pneumatic units include a magnetic starter, the CP simplex models list a CPXHT-25, and the BendPak TSP-580V-601 lists no magnetic starter but does include an electronic drain valve. Automatic timed tank drains appear on the BelAire QP series, the BelAire 438VE and 438VE4, the CP Premium Iron Series and the EMAX Premium and Industrial Plus units. The EMAX Industrial and Silent Air units list a manual drain, the BendPak lists an electronic drain valve, and most other listings do not state a drain type.