The Castair D10312HC3-S is a 20 total horsepower duplex two-stage air compressor on a 120-gallon horizontal ASME tank, wired for three-phase electricity, running the HC3 pump at 570 RPM. It delivers 70 CFM at 175 PSI combined from two 10 HP cast iron pumps, weighs 1,740 lbs, and measures 94" x 28" x 57". The HC3 pump's 570 RPM speed is the defining difference from the HC2 version — slower RPM means lower operating temperatures, quieter operation, and longer pump life, in a frame that is 9" longer to accommodate the larger displacement cylinders.
Three-Phase + HC3 Pump: The Production Floor Choice
The D10312HC3-S combines two advantages:
- Three-phase power — cooler, more efficient motor operation, smoother starts, longer motor life compared to single-phase at the same HP rating
- HC3 pump at 570 RPM — lower heat generation, extended valve and ring life, quieter operation than the HC2 at 758 RPM
For a shop that runs the compressor at high utilization — multiple shifts, continuous spray operations, heavy pneumatic tool use — this combination is the right long-term choice even though it costs more upfront than the HC2 version.
Pump and Motor Specifications
- Configuration: Duplex (two pumps, two motors)
- Total HP: 20 HP (2 x 10 HP)
- Phase: Three-phase
- Pump RPM: 570 (HC3 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): 94" x 28" x 57"
- Weight: 1,740 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 life and quiet operation
- HC3 pump at 570 RPM — slowest pump in the 120gal duplex lineup for this HP class
- Tapered roller bearings at both ends of crankshaft
- Precision steel connecting rods with automotive-type rod insert bearings
- Disc and spring valves for 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 — lighter, shorter frame
- D10312HC3-S — 3-phase, 120gal, HC3 570 RPM, 94x28x57, 1,740 lbs — slower pump (this unit)
- D10324HC2-S — 3-phase, 240gal, HC2 758 RPM, 1,760 lbs — larger tank
- D10324HC3-S — 3-phase, 240gal, HC3 570 RPM, 2,190 lbs — maximum configuration
When Does a Shop Need This
Choose the D10312HC3-S when: You have three-phase service, run the machine at high utilization (extended daily hours, continuous processes), care about noise level in the shop, and the 120-gallon tank provides adequate storage between cycles.
Step up to D10324HC3-S if spray painting, sandblasting, or other continuous high-draw processes exhaust 120 gallons faster than the pumps can replenish — the 240-gallon version eliminates pressure sag during peak demand.
Step down to D10312HC2-S if the 330 lbs weight difference and 9" frame length difference matter for your installation, and if noise/temperature are not primary concerns.
Technical Specifications
- Model: D10312HC3-S
- Manufacturer: Castair (Cast Air, Inc.) — Spicer, Minnesota
- Total HP: 20 HP (2 x 10 HP)
- Phase: Three-phase
- Pump RPM: 570 (HC3)
- CFM @ 0 PSI: 90
- CFM @ 175 PSI: 70
- Tank: 120 gallon, horizontal, ASME, powder coated
- Dimensions (LxWxH): 94" x 28" x 57"
- Weight: 1,740 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 industrial and duplex compressors since 2016. We can help you compare the HC2 vs. HC3 pump and evaluate whether 120 or 240 gallons suits your shop's peak demand. Free shipping, free technical support at 866-217-0063, and the full Castair manufacturer warranty.
Call 866-217-0063 for quick answers and help!
