Rotary Screw

The four configurations in this category

The same air end is sold in several packages. The difference decides how much you still have to buy after delivery.

• Cabinet only / base mounted. The compressor and its enclosure, nothing else. The EMAX Industrial listings state plainly: "This unit is a floor mount model and does not include the receiving tank or air dryer." The variable speed listings state "Designed For Use With Stationary Air Receiver (Not Included)." Chicago Pneumatic sells the equivalent as Base Mounted.
• Tank mounted. Compressor bolted to a horizontal receiver. Chicago Pneumatic QRS 3, 5 and 7.5 list a 60 gal. ASME/CRN receiver tank; QRS 10 and 15 list a 120 gal. ASME/CRN tank. EMAX tank-mounted Industrial units come on 80 gal. or 120 gal. receivers depending on model.
• Tank mounted with dryer. Adds a refrigerant dryer, so air is dried at the source. The EMAX ERIK listings describe "a patented swingarm mounted air dryer for small foot print and easy maintenance." Chicago Pneumatic offers this on all eight QRS sizes.
• Variable speed drive (VSD). Only EMAX offers it here, across 23 listings. EMAX states the Drive-Tek design "Reduces energy demand up to 33%," and the 25 HP direct drive listing claims "up to 7X starting amp savings and up to 40% savings while the unit is in operation." From 15 HP up the VSD units also carry a higher maximum pressure, 167 psi against 145 psi on the fixed-speed Industrial line. Below 15 HP both lines list 145 psi.

The series you are actually choosing between

EMAX Industrial Rotary Screw (ERI and ERIK, 18 listings)

Belt driven, 1750 RPM motor, MANN filters, 8000 HR oil, and the Logik 9 smart controller, which the listings describe as setting pressures, alarms and schedules, with master/slave control so two machines share the load. Maximum pressure is 145 psi. Air delivery at 110 psi runs 19.42 cfm at 5 HP, 24.01 at 7.5 HP, 39.9 at 10 HP, 56.85 at 15 HP, 76.99 at 20 HP, 98.88 at 25 HP and 111.6 at 30 HP. Single phase exists only up to 10 HP.

EMAX Variable Speed (ERV and ERVK, 23 listings)

Two mechanical layouts sit inside this group. From 5 HP through 20 HP the specification tables read Drive Type: Belt (the 15 HP lists 2 belts, the 20 HP lists 3); from 25 HP through 100 HP they read "Belt Count: Direct Drive." Maximum pressure is 167 psi from 15 HP up. The 5 HP and 7.5 HP variable speed cabinets list 145 psi max, the same as the fixed-speed Industrial line. The 5 HP lists 20 cfm at 110 psi. The rest publish a bare cfm figure with no reference pressure stated: 62 cfm at 15 HP, 85 at 20 HP, 106 on the 25 HP direct drive, 235 at 50 HP and 424 at 100 HP. Ask for the model spec sheet if you need the delivery at your working pressure. EMAX also offers single-phase variable speed at 15 HP and 20 HP, useful if you have no three-phase service.

Chicago Pneumatic QRS, small frame (QRS 3 through QRS 15)

QRS stands for Quiet Rotary Screw, and the sound figures are published: 61 dB(A) on the QRS 3, 62 on the QRS 5, 66 on the QRS 7.5, 65 on the QRS 10 and 69 on the QRS 15. The listings position these for "a tire shop, maintenance shop, vehicle body shop, paint shop or automotive dealership," and state you "Get 15% More Air Using 12% Less Energy Compared to Its Predecessor." The QRS 3, 5 and 7.5 publish two pressure points, 116 psi and 145 psi; the QRS 10 and 15 publish 125 psi and 150 psi.

Chicago Pneumatic QRS, large frame (QRS 20, 25, 30)

A different machine under the same name: ES4000 Basic Controller, Wye-Delta reduced voltage start, permanently aligned belt drive, load/no-load with intelligent shutdown, and a space saving design under 16 sq. ft. Chicago Pneumatic publishes four pressure points for these, the most useful data here if your plant runs above 125 psi: the QRS-20 delivers 93.2 acfm at 100 psig but only 69.3 acfm at 175 psig. The QRS-25 goes 109.8 down to 84.5 acfm, the QRS-30 128.2 down to 97.5 acfm. Those four columns are air delivery measured at 100, 125, 150 and 175 psig; they are not the pressure rating of the machine. The features list on these pages is inconsistent for the QRS 20: only the QRS 20 BM-3 states 150 psig standard, while the QRS 20 BMD-3, TM-3 and TMD-3 state 125 psig standard, the same as the QRS 25 and QRS 30.

What you need in the building before it arrives

Power and phase. Chicago Pneumatic lists two phase options: single phase 230V TEFC, and 3-phase 208-230/460V and 575V TEFC. The QRS 3, 5 and 7.5 come in both. From the QRS 10 up, the specification table, the features list and the SKU all say three phase, although the Phase options block on those pages still repeats a single-phase line - treat it as boilerplate and confirm on the order. EMAX three-phase units list 208/230/460; EMAX single-phase units list 230V, plus or minus 10 percent.

Breaker size. Where the EMAX listings publish it, plan for it. The 7.5 HP single-phase Industrial lists 28.8 A at 1.15 service factor with a 40 A recommended breaker; the 10 HP single-phase tank package, 38.3 A and a 55 A breaker; the 15 HP three-phase tank package, 43.1 A, 237 locked rotor amps and a 60 A breaker; the 20 HP three-phase tank package, 57.5 A, 331 locked rotor amps and an 80 A breaker. At the top of the range the 50 HP variable speed lists 143.8 A and a 160 A breaker, the 100 HP 287.5 A and a 320 A breaker. Where a listing does not publish an amp draw, consult that model's spec sheet before the electrician quotes.

Floor space and door width. Base-mounted Chicago Pneumatic units are compact: 24.4 x 24.8 x 37.4 in. for the QRS 3, 5 and 7.5; 33.7 x 26.6 x 38.6 in. for the QRS 10 and 15; 45 x 31 x 49 in. for the QRS 20, 25 and 30. Tank-mounted versions get long rather than tall: 56.3 x 23.6 x 49.6 in. on the QRS 3, 76.2 x 25.4 x 57.9 in. on the QRS 10 and 15, 75 x 31 x 72 in. on the QRS 20 and 30. EMAX Industrial (ERI) cabinets run 35 x 24 x 41 in. at 5 to 10 HP, 38 x 30 x 49 in. at 15 and 20 HP and 46 x 38 x 57 in. at 25 and 30 HP. The variable speed (ERV) cabinets are different: 26 x 34 x 43 in. at 5 to 10 HP, 38 x 31 x 49 in. at 15 and 20 HP, 56 x 38 x 57 in. at 25 HP and 89 x 52 x 72 in. at 100 HP.

Rigging weight. From 276 lb on the QRS 3 base mounted to 3,775 lb uncrated on the 100 HP EMAX. Crated weights run heavier: the EMAX 10 HP single-phase tank package lists 660 lb uncrated but 1,503 lb crated at 86 x 49 x 78 in. Plan a forklift and a dock.

Plumbing and drains. EMAX Industrial outlet size is 1/2 in. at 5 HP, 3/4 in. at 7.5 and 10 HP, and 1 in. from 15 HP up. Tank drains differ within one series: the 5 HP EMAX 80-gallon package lists a manual drain, while 7.5 HP and larger EMAX tank packages list automatic. Chicago Pneumatic tank-mounted units list a low-loss timer drain for condensate. Oil capacity, where published, is 1.33 gallons at 7.5 to 10 HP, 1.5 at 15 to 20 HP, 2.5 at 25 HP, 4.5 at 50 HP and 7.9 at 100 HP.

Certifications declared on these listings

• UL / cUL / CSA. Chicago Pneumatic QRS 3 through QRS 15 list a "UL, cUL and CSA approved control panel"; QRS 20 through QRS 30 list a "UL and cUL approved control panel." Most EMAX listings that publish a certifications row show UL/CSE; the 5 HP 80-gallon tank package shows UL, ASME. Many EMAX listings publish no certifications row at all.
• ASME. Chicago Pneumatic receiver tanks are listed as 60 gal. or 120 gal. ASME/CRN. The EMAX 5 HP 80-gallon package lists UL, ASME. The EMAX variable speed 15 HP package describes its 120 gallon tank as made in the USA, ring based to prevent cracking, with standard NPT ports, ASME, NBBI and CRN approvals, rated up to 450 degrees F.
• NEMA 1 electrical protection on the Chicago Pneumatic QRS units, with a vibration isolated assembly and a spin-on oil filter and separator.

Model comparison

Notes where two listings disagree

A few product pages here contain internal conflicts. Trust the specification table over the marketing paragraph, and confirm the disputed item in writing on the order.

• The EMAX 7.5 HP single-phase tank package (ERIK070001) is named as an 80 gallon unit but its specification row reads 120. Confirm tank size on the order.
• The EMAX 5 HP and 7.5 HP single-phase variable speed cabinets (ERV0050001, ERV0070001) are named 1PH but their specification rows read Three. Confirm phase before ordering; the same mismatch may apply to the 10 HP listing.
• The 5 through 20 HP variable speed listings are named Direct Drive but their specification tables read Belt. Trust the table.
• The EMAX 25 HP direct drive paragraph cites 111 cfm at 100 psi while its table lists 106 cfm. The table is the more reliable figure.
• The EMAX 25 HP direct drive paragraph cites up to 70,000 running hours while its specification row reads 100,000. The table is the more reliable figure.
• The Chicago Pneumatic QRS 10 and QRS 15 pages keep a Phase options block that still offers a single phase, 230V TEFC motor, while the specification table, the features list and the SKU all read three phase. Treat the block as boilerplate and confirm phase on the order.
• Every Chicago Pneumatic base-mounted listing repeats a receiver tank bullet inherited from the tank-mounted version: 60 gal. on the QRS 3, 5 and 7.5, 120 gal. on the QRS 10 and 15. A base-mounted unit does not ship with a tank.

Frequently asked questions

How much cfm do I actually need?

Add the cfm draw of the tools you run at the same time, then match a model whose published delivery exceeds that at your working pressure, not at its lowest pressure point. The Chicago Pneumatic QRS-20 gives 93.2 acfm at 100 psig but 78.4 acfm at 150 psig. Size off the pressure you will actually run, or the machine is undersized on day one.

Do I need three-phase power?

Not necessarily. Single-phase options exist on the Chicago Pneumatic QRS 3, 5 and 7.5 (230V TEFC) and on the EMAX Industrial line up to 10 HP. On the EMAX variable speed line, only the 15 HP and 20 HP listings declare single phase in their specification table (ERV0150001 reads Phase 1). The 5, 7.5 and 10 HP listings are named 1PH but their specification row reads Motor Phase Three - confirm phase in writing before ordering any of them. Above those sizes the listings are three phase, 208-230/460V, with 575V also a Chicago Pneumatic option.

What is the difference between base mounted, tank mounted, and tank mounted with dryer?

Base mounted or cabinet only is the compressor alone, with no receiver and no dryer. Tank mounted adds the ASME receiver. Tank mounted with dryer adds a refrigerant dryer so moisture is removed before the air reaches your lines, which matters for paint work and for tools you do not want rusting inside.

Is a variable speed unit worth the difference?

It depends on how variable your demand is. EMAX credits the Drive-Tek design with reducing energy demand up to 33 percent, and its 25 HP listing claims up to 7X starting amp savings. A shop with steady demand gets less from that than one whose demand swings. From 15 HP up the variable speed models also list a higher 167 psi maximum; below 15 HP both lines list 145 psi. The variable speed specification rows list a 100,000-hour estimated pump life against 60,000 hours on the fixed-speed Industrial line.

How loud are these?

Chicago Pneumatic publishes sound levels: 61 dB(A) on the QRS 3, rising to 70 dBA on the QRS-30. EMAX listings describe a sound proof or sound attenuated cabinet but publish no decibel figure, so if a noise limit drives your decision, ask for that model's spec sheet.

Which listings ship freight-free?

All 27 Chicago Pneumatic QRS listings are flagged for free shipping; the 41 EMAX listings are not, so freight is quoted separately on those. The Chicago Pneumatic pages also carry a manufacturer note that sales tax is collected in all states.