Air Compressors

Piston or rotary screw: what actually changes

Duty cycle. Where EMAX publishes a duty cycle, its stationary pistons read 0.6 and its rotary screws read 1 - EMAX does not define what those figures mean, and the Premium piston listings that read 0.6 also carry a "Continuous Run: Y" row. Nineteen of the 41 EMAX screw listings, including nine of the ten fixed-speed Industrial cabinets, publish no duty cycle at all. The QRS line is listed with continuous operating capability and no cool-down period. If your shop runs a paint booth or several bays at once, ask for the duty rating in writing before you order.

Noise. The QRS screws publish 61 dB(A) on the QRS 3, 65 on the QRS 10, 67 on the QRS 20 and 70 on the QRS 30. The BendPak pistons publish 72 dBA on the 5 HP BP-5179111, 75 dB on the 10 HP BP-5179114 and 78 dB on the 7.5 HP BP-5179112.

Pump life. EMAX lists an estimated pump life of 70,000 hours for its two-stage pressure-lubricated pumps, while the Industrial Plus 20 and 25 HP listings describe the complete unit as designed for up to 50,000 hours - the pump outlives the package. Its fixed-speed Industrial screws are listed at 60,000 hours and its variable-speed direct-drive screws at 100,000.

Pressure. Nearly every piston here tops out at 175 PSI; the exceptions are the BelAire 4916V at 165 PSI and the single-stage 6061V at 135 PSI. The screws run lower: EMAX Industrial screws at 145 PSI max; the EMAX variable-speed line splits, 145 PSI on the 5, 7.5 and 10 HP cabinets and on the 7.5 HP VSD packages, and up to 167 PSI from 15 HP up - check the Max PSI row on the model you pick, because the 15 HP single-phase (167) and three-phase (145) cabinets differ. The QRS line splits by size as well: the QRS 3 through 15 publish two working pressures (116/145 psig on the 3, 5 and 7.5; 125/150 psig on the 10 and 15), while the QRS 20, 25 and 30 publish acfm at 100, 125, 150 and 175 psig.

Capacity range, with the models that mark it

• Portable: RCP-508H, 5.5 HP Honda recoil start on twin 4-gallon tanks, 12.4 CFM, 143 lb.
• 5 HP stationary: 15.4 to 18.5 CFM at 100 PSI - BelAire 4918VN at 15.4 and 4916V at 16.1, RCP-C581VS and BelAire 438V at 18, RCP-583V at 18.5. EMAX ESP05V080I1 lists 19 CFM with no reference pressure and 17 CFM at its 175 PSI maximum.
• 7.5 HP: BelAire 438VL and Chicago Pneumatic RCP-C7583V at 23 CFM at 100 PSI (the 438VL also lists 21 CFM at 175 PSI), RCP-7583VS at 25.3 CFM at 100 PSI. EMAX ESP07V080V1 lists 31 CFM with no reference pressure and 26 CFM at its 175 PSI maximum.
• 10 HP: 35 CFM at 100 PSI on the BelAire 6312V and the RCP-C10123V. EMAX ESP10V080V1 lists 38 CFM with no reference pressure and 34 CFM at its 175 PSI maximum. The BendPak BP-5179114 listing is inconsistent with itself (41 CFM in one row, 35 CFM in the row that normally carries the rating pressure) and states no reference pressure, so confirm it on the spec sheet.
• 15 to 20 HP duplex: RCP-C15123D at 46, BelAire 3312DL at 50.5, RCP-C20203D at 70 on a 200-gallon tank.
• 20 to 25 HP single pump: EMAX EP20H120V3 at 82 and EP25H120V3 at 96, on 120-gallon horizontal tanks.
• Rotary screw: QRS 3 at 12.6 CFM (116 psig) up to QRS 30 at 128.2 ACFM (100 psig); EMAX variable-speed at 85 CFM (20 HP), 235 (50 HP), 353 (75 HP) and 424 (100 HP), none of those EMAX figures with a stated reference pressure.

Space, tank and footprint

Tank sizes in the range are 2 x 4, 20, 30, 60, 80, 120 and 200 gallons, and orientation drives the footprint more than horsepower does. An 80-gallon vertical RCP-583V measures 39 x 24 x 77 in.; the same pump on a horizontal tank (RCP-583H) is 71 x 24 x 49 in. A 120-gallon vertical is 42 x 30 x 74 in., a 120-gallon horizontal duplex 77 x 27 x 56 in. at 10 and 15 HP and 81 x 27 x 52 in. at 20 HP, and the 200-gallon duplex RCP-C20203D 85 x 27 x 52 in. Check ceiling and doorway against the crated dimensions: the EMAX EI07V080V1 stands 75 in. uncrated but ships in a crate 48 x 46 x 87 in.

Rotary screws are sold four ways, and the difference is a tank and a dryer: base-mounted (cabinet only), base-mounted with dryer (QRS 20, 25 and 30), tank-mounted, and tank-mounted with dryer. Careful with the base-mounted listings: the QRS base-mounted pages repeat the receiver tank bullet from their tank-mounted siblings, but the weight rows say otherwise - a QRS 3 is 276 lb base-mounted against 397 lb tank-mounted, and the EMAX variable-speed cabinets state outright that the receiver is not included. Treat a base-mounted unit as the cabinet only and confirm the receiver on the order. Tank-mounted QRS models come on a 60-gallon ASME/CRN receiver (QRS 3, 5, 7.5) or a 120-gallon one (QRS 10, 15); the receiver size is not stated on the QRS 20, 25 and 30 listings, so confirm it on the spec sheet. Tank-mounted-with-dryer versions put the dryer in the same package, about 55 lb more on a QRS 5.

Power: where most orders go wrong

Single-phase models here run 208-230 V. Three-phase models run 208-230 V or 460 V, and the three-phase QRS line is also offered at 575 V. The same machine draws very different current depending on which you have. Chicago Pneumatic's 5 HP Iron Series is the clean example: the RCP-C581VS at 208-230 V single-phase draws 25-23 A and calls for a 40 A breaker; the RCP-C583VS at 208-230 V three-phase draws 14-13.2 A and calls for 25 A; the RCP-C583VS4 at 460 V three-phase draws 6.6 A and calls for 15 A. All three deliver 18 CFM at 100 PSI and top out at 175 PSI.

The gap widens with size. The 20 HP duplex is two part numbers: the RCP-C20123D draws 52-50 A on 208-230/3 and calls for a 90 A breaker; the RCP-C20123D4 draws 25 A on 460/3 and calls for 60 A. Same 70 CFM at 100 PSI, same 1,395 lb. At the top of the range the EMAX ERV1000003D lists 287.5 FLA and a 320 A recommended breaker. Where a listing gives a recommended breaker, that is the figure to hand your electrician.

With no three-phase service the single-phase side of the catalog is still deep: BelAire 3112D (10 HP, 120 gal, 37.2 CFM) and 3112DL (15 HP, 50.5 CFM), the RCP-C10121D and RCP-C15121D duplex units, and single-phase EMAX screws up to 20 HP.

For service trucks there is no panel at all. The EMAX EGES1860ST pairs an 18 HP Honda GX630 with a 5-gallon fuel tank and 34 CFM at 110 PSI; its listing notes it needs only a 12-volt battery and two cables. BelAire's gas units cover 13 HP (4G3HHL, 23 CFM at 100 PSI, 30-gallon horizontal), 14 HP (4G3HKL) and 16 HP Vanguard (6G3HV, 35 CFM, electric and recoil start). The EGES14020T is a 14 HP Kohler wheelbarrow unit combining compressor, generator and welder on a 20-gallon tank at 19 CFM.

Air treatment

Twelve EMAX refrigerated dryers cover 30, 58, 115 and 144 CFM on 115 V single-phase; 288 and 575 CFM on 230 V three-phase; and 288, 575, 850, 1,200, 1,600 and 2,000 CFM on 460 V three-phase. All are listed at a 37 F dew point, R134A refrigerant, 230 PSI maximum, 140 F maximum inlet and 122 F maximum ambient temperature. Connections run from 1/2 in. on the 30 CFM unit to 3 in. on the 850 CFM, with a DN 100 flange on the two largest, and breakers are modest: 6 A for the 30 CFM, 20 A for the 144 CFM. The Chicago Pneumatic CPX10 handles 12.4 CFM through a 3/4 in. connection at 230 V, 170 W.

Six EMAX bundles ship a Premium compressor with a dryer already matched: the 5 HP (19 CFM) and 7.5 HP (31 CFM) units with the 30 CFM dryer, and the 10 HP (38 CFM) units with the 58 CFM dryer. Note that the 7.5 HP bundle puts a 31 CFM compressor in front of a 30 CFM dryer, so if that unit will run near full output, step up to the 58 CFM dryer. Those listings note the package does not include the connection line.

Certifications declared on these listings

Air receivers across all four brands are ASME code tanks, and EMAX states its ASME tank is approved for all 50 states. Chicago Pneumatic Iron Series tanks are ASME and CRN certified and National Board registered, with an ASME-certified safety valve on tank and pump. EMAX piston models list ETL, ASME and CRN; Industrial Plus lists CSA, ASME and ETL; the rotary screws list UL. BendPak lists UL, CSA and ASME on the 5 HP BP-5179111 and on the two 7.5 HP units, and ASME on the 10 HP BP-5179114, and carries a California Prop 65 warning. The QRS 3 through 15 use a UL, cUL and CSA approved control panel; the QRS 20, 25 and 30 list a UL and cUL approved panel. All of them list NEMA 1 electrical protection, and EMAX belt guards are described as OSHA approved.

Comparison of representative models

Reading the spec sheets: three things to watch

A few listings carry manufacturer copy that contradicts their own spec table. Trust the model name and the table.

• The EMAX EGES1860ST is a 60-gallon unit per its name and spec table; the paragraph carried over from the 30-gallon EGES1830ST still says 30 gallons.
• BelAire's Iron Series splits by phase: the 418 models are single-phase (the 418VE spec table reads Phase 1) and the 438 models are three-phase, but a "MUST Have Three-Phase Electric Power" bullet appears on some 418 pages. Go by the voltage and phase row.
• The BendPak names do not line up. The 5 HP BP-5179111 is titled Elite but its body calls it TSP-5 Patriot Series (TSP-580V-601). The two 7.5 HP units, BP-5179112 (1-phase) and BP-5179113 (3-phase), are titled V-Max Elite but their bodies call them V-Max Patriot (VMP-7580V-601 and -603). Only the 10 HP BP-5179114 is a V-Max Elite (VMX-10120V-603). Go by the model number.

Frequently asked questions

Which CFM number should I use to size the compressor?

Use CFM at the pressure you will actually work at, not displacement. The RCP-583V lists 22.4 CFM displacement and 18.5 CFM at 100 PSI - same machine. The QRS 30 delivers 128.2 ACFM at 100 psig but 97.5 ACFM at 175 psig. If your tools need 175 PSI, size against the 175 PSI figure.

Do I need three-phase power?

Not for most of the range. Single-phase 208-230 V models go up to 15 HP piston (BelAire 3112DL, Chicago Pneumatic RCP-C15121D) and 20 HP rotary screw (EMAX ERV0200001). Above that the catalog is three-phase. Phase also changes current draw sharply: the same 5 HP Iron Series pump needs a 40 A breaker on single-phase and 15 A on 460 V three-phase.

What does "Elite", "Premium" or "full features" add?

On BelAire, the Elite version (438VE against 438V) adds an automatic tank drain, a belt guard aftercooler and a low oil level switch, at the same 18 CFM. Chicago Pneumatic's full-featured Iron Series models (RCP-C10123V against RCP-C10123VS) add the same three. EMAX Industrial Plus adds a timed automatic drain over the Industrial line. Separately, the EMAX Premium (ESP) listings add an automatic drain, a belt tension adjuster and a continuous-run row that the Industrial (EI) listings mark "N".

Does a base-mounted rotary screw include a tank?

Careful here: the QRS base-mounted listings repeat the "60 gal. ASME/CRN receiver tank" bullet from their tank-mounted siblings, but the weight rows say otherwise - a QRS 3 is 276 lb base-mounted against 397 lb tank-mounted, and the EMAX variable-speed cabinets state outright that the receiver is not included. Treat a base-mounted unit as the cabinet only and confirm the receiver on the order.

Do I need a refrigerated dryer?

If you spray paint or run tools that suffer from moisture, yes - the dryer listings describe removing water before it reaches the distribution system. Size the dryer against the CFM you will actually push through it. EMAX's own bundles pair the 5 HP (19 CFM) Premium unit with the 30 CFM dryer and the 10 HP (38 CFM) with the 58 CFM dryer; the 7.5 HP bundle pairs a 31 CFM compressor with the 30 CFM dryer, so if that unit will run near full output, step up to the 58 CFM dryer.

Can I replace just the pump?

For an EMAX unit with a sound tank and motor, six bare pumps with flywheel are listed separately: 3 HP / 13 CFM, 5 HP / 18 CFM and 7.5 HP / 32 CFM single-stage splash-lubricated, plus 5 HP, 10 HP and 25 HP / 98 CFM two-stage pressure-lubricated. These six pumps are listed for reference and are not set up for online checkout; match the pump model on your compressor's spec table and call 800-562-4791 to order.

If you are between two sizes, or unsure what your panel will carry, call 800-562-4791 and we will size it against your shop's air demand.