Castair 10 HP Duplex Two-Stage Air Compressor — 35 CFM @ 175 PSI, 120 / 240 Gal ASME Tank
The Castair Duplex 10 HP is a two-stage industrial air compressor that runs two independent 5 HP pump-and-motor sets on a single ASME-certified horizontal tank. The duplex design is the whole point: run one pump for light demand, run both together for double the output, or let them alternate automatically to share wear — and if one pump ever needs service, the other keeps your shop running. With dual full cast iron, oil-lubricated pumps delivering up to 44 CFM at 0 PSI and 35 CFM at 175 PSI, it's built for medium shops, HVAC service operations, and any application that needs steady air plus the security of a built-in backup. Hand-built to order by Castair, a family-owned Minnesota manufacturer since 1991.
Why It's Different: Each pump uses a V-twin cylinder design for 360-degree cooling, tapered roller bearings at both ends of the crankshaft, and stainless disc-and-spring valves rated for up to 10× the lifespan of competitor reed valves. Slow pump RPM and a larger bore/stroke mean cooler, quieter operation and longer pump life. A centrifugal unloader gives load-less startups, the four-ring pistons minimize oil carry-over, and an oil sight glass makes maintenance checks effortless. Every unit ships with the magnetic starter mounted and wired.
Best For: Medium to large shops, HVAC installation and service trucks, automotive repair, and manufacturing operations that need reliable high-duty air output with redundancy.
Configuration: Choose single-phase or three-phase power, a 120-gallon or 240-gallon ASME horizontal tank, and standard (767 RPM) or slow-speed (420 RPM) pump build. All configurations deliver 44 CFM @ 0 PSI / 35 CFM @ 175 PSI.
⚠️ BEFORE YOU ORDER — PLEASE READ: This is a heavy-duty, built-to-order industrial compressor.
• Electrical: requires a dedicated 208–230V circuit (single-phase or three-phase, per your selected model), installed by a licensed electrician with proper grounding. Magnetic starter comes mounted and wired.
• Lead time: all Castair units are built to order — confirm current production lead time before purchase.
• Weight & placement: 1,080–1,650 lb depending on configuration; requires a level floor rated for the load, adequate ventilation for heat dissipation, and freight handling for delivery.
It is the customer's responsibility to verify electrical service, floor space, and ventilation before purchase and installation.
Features
-
Duplex design — two independent 5 HP pump/motor sets run one, both, or auto-alternating for redundancy
- Up to 44 CFM @ 0 PSI / 35 CFM @ 175 PSI
- Two-stage, dual full cast iron oil-lubricated pumps
-
V-twin cylinder design for 360° cooling and longevity
-
Tapered roller bearings at both ends of the crankshaft for reduced friction
-
Stainless disc & spring valves — up to 10× the lifespan of reed valves
-
Four-ring pistons for higher efficiency and minimal oil carry-over
-
Centrifugal unloader for load-less startups
-
ASME-certified, powder-coated horizontal tank for safety and corrosion resistance
- Rigid metal belt guards, copper discharge & unloader tubes, oil sight glass
-
Magnetic starter mounted & wired standard
- Single-phase or three-phase | 120 or 240 gal tank | Built to order in Minnesota
Specifications
| Castair Duplex 10 HP (2×5 HP) — 44 CFM @ 0 PSI / 35 CFM @ 175 PSI |
| Model |
Phase |
Pump RPM |
Tank (Gal) |
L × W × H (in) |
Weight (lb) |
| D5112HC1-S |
Single |
767 |
120 |
85 × 28 × 57 |
1,110 |
| D5124HC-S |
Single |
767 |
240 |
85 × 30 × 64 |
1,460 |
| D5112HC2-S |
Single |
420 |
120 |
85 × 28 × 57 |
1,300 |
| D5124HC2-S |
Single |
420 |
240 |
85 × 30 × 64 |
1,650 |
| D5312HC1-S |
Three |
767 |
120 |
85 × 28 × 57 |
1,080 |
| D5324HC1-S |
Three |
767 |
240 |
85 × 30 × 64 |
1,430 |
| D5312HC2-S |
Three |
420 |
120 |
85 × 28 × 57 |
1,270 |
| D5324HC2-S |
Three |
420 |
240 |
85 × 30 × 64 |
1,620 |
| Shared Specifications |
| Manufacturer |
Castair (Spicer, Minnesota — family-owned since 1991) |
| Type |
Two-stage electric duplex air compressor (horizontal tank) |
| Total HP |
10 HP (2 × 5 HP) |
| Output |
44 CFM @ 0 PSI | 35 CFM @ 175 PSI |
| Pump |
Two-stage, dual full cast iron, oil-lubricated, V-twin |
| Voltage |
208–230V, single-phase or three-phase |
| Tank |
120 or 240 gal, ASME-certified, powder-coated horizontal |
| Controls |
Magnetic starter mounted & wired; centrifugal unloader |
| Brand |
Castair |
What's Included
- Dual two-stage cast iron pumps and dual motors on one ASME horizontal tank
- Magnetic motor starter — mounted and wired
- Intake filter / noise silencers
- Metal belt guards, copper discharge & unloader tubing, oil sight glass
- (Factory-mounted options available — low oil control, hour meter, alternator, electronic auto drain, dual control, intake silencers, belt tensioner, aftercooler. Contact us to configure.)
Manuals & Documentation