The Castair D10312HC2-S is a 20 total horsepower duplex two-stage air compressor on a 120-gallon horizontal ASME tank, wired for three-phase electricity. It runs two 10 HP cast iron pumps at 758 RPM (HC2 configuration), delivers 70 CFM at 175 PSI combined, and weighs 1,410 lbs. The magnetic starter is mounted and wired at the factory. This is the three-phase equivalent of the D10112HC2-S — same pump, same tank, same output — but the three-phase power system means better motor efficiency, lower running current, and longer motor life at this horsepower level.
Three-Phase Advantage at 2x10HP
If your shop has three-phase service, this is the preferred configuration over single-phase at this power level. Three-phase motors:
- Draw lower amperage for the same horsepower output — easier on your electrical service
- Start more smoothly — less in-rush current stress on breakers and motor windings
- Run cooler due to balanced load across all three legs
- Last longer — three-phase motors are simpler in construction (no start capacitors, no centrifugal switches)
The D10312HC2-S also weighs 60 lbs less than its single-phase counterpart (1,410 lbs vs. 1,470 lbs), though the dimensions are identical at 85" x 28" x 57".
Pump and Motor Specifications
- Configuration: Duplex (two pumps, two motors)
- Total HP: 20 HP (2 x 10 HP)
- Phase: Three-phase
- Pump RPM: 758 (HC2 pump)
- CFM at 0 PSI: 90 CFM combined
- CFM at 175 PSI: 70 CFM combined
- Max Pressure: 175 PSI
- Stage: Two-stage
Tank and Physical Specs
- Tank Capacity: 120 gallons, horizontal ASME
- Dimensions (LxWxH): 85" x 28" x 57"
- Weight: 1,410 lbs
- Tank Finish: Powder coated
- Safety Valve: ASME rated, installed
- Magnetic Starter: Mounted and wired (factory installed)
Cast Iron Pump Features
- All cast iron construction for long service life and quiet operation
- 758 RPM HC2 pump — slow speed for extended valve life and quieter operation
- Tapered roller bearings at both ends of crankshaft
- Precision steel connecting rods with automotive-type rod insert bearings
- Disc and spring valves for easy service and reliability
- 4-ring pistons for efficiency and reduced oil carry-over
- Centrifugal unloader for loadless starts
Three-Phase 2x10HP Duplex Comparison
- D10312HC2-S — 3-phase, 120gal, HC2 758 RPM, 85x28x57, 1,410 lbs (this unit)
- D10324HC2-S — 3-phase, 240gal, HC2 758 RPM, 85x30x64, 1,760 lbs — more storage
- D10312HC3-S — 3-phase, 120gal, HC3 570 RPM, 94x28x57, 1,740 lbs — slower/quieter pump
- D10324HC3-S — 3-phase, 240gal, HC3 570 RPM, 94x30x64, 2,190 lbs — maximum configuration
When Does a Shop Need This
Choose the D10312HC2-S when: You have three-phase service, need 60-70 CFM sustained output, want duplex redundancy, and the 120-gallon tank provides adequate storage for your duty cycle.
Step up to D10324HC2-S if your shop runs continuous high-draw processes — spray painting, sandblasting — that exhaust 120 gallons between pump cycles.
Step up to D10312HC3-S if noise level matters or you plan to run the machine at a very high duty cycle; the 570 RPM HC3 pump runs cooler and quieter.
If you do not have three-phase service, the D10112HC2-S is the single-phase equivalent with the same output specs.
Technical Specifications
- Model: D10312HC2-S
- Manufacturer: Castair (Cast Air, Inc.) — Spicer, Minnesota
- Total HP: 20 HP (2 x 10 HP)
- Phase: Three-phase
- Pump RPM: 758 (HC2)
- CFM @ 0 PSI: 90
- CFM @ 175 PSI: 70
- Tank: 120 gallon, horizontal, ASME, powder coated
- Dimensions (LxWxH): 85" x 28" x 57"
- Weight: 1,410 lbs
- Magnetic Starter: Included, factory mounted and wired
- Safety Valve: ASME rated, installed
Why Buy From Air Compressor Factory Direct?
We have been selling Cast Air duplex compressors since 2016. Before you order, we will confirm your electrical service can support two 10 HP three-phase motors simultaneously and help you spec any factory-mounted options (low oil control, auto drain, aftercooler). Free shipping, free technical support at 866-217-0063, full manufacturer warranty.
Call 866-217-0063 for quick answers and help!
