Castair I7312HC2-S: 7.5 HP Three-Phase Industrial Air Compressor, 120-Gallon Horizontal Tank
The Castair I7312HC2-S is a 7.5 horsepower, three-phase industrial reciprocating air compressor on a 120-gallon horizontal ASME tank with a factory-mounted aftercooler. This is the largest horizontal tank option in the 7.5 HP three-phase Castair lineup — the three-phase equivalent of the I7112HC2-S single-phase model.
If your shop has three-phase power, this is the unit to buy over the single-phase equivalent. Three-phase motors are more efficient, run cooler, and last longer at the same HP rating. The I7312HC2-S delivers the same pump performance as the single-phase 120-gallon model but draws current more evenly across three phases, reducing motor stress significantly. It also weighs 30 lbs less than the single-phase version at 820 lbs vs. 850 lbs.
Three-Phase vs. Single-Phase at 7.5 HP
- Motor efficiency: Three-phase motors are more efficient than single-phase at the same HP
- Motor longevity: Even current draw across three phases means less heat, less vibration, longer motor life
- Starting torque: Three-phase motors start smoothly without capacitor banks
- Weight: 820 lbs vs. 850 lbs for the I7112HC2-S single-phase equivalent
C2 Pump — Industrial Cast Iron Construction
- All cast iron: Cylinder, head, crankcase
- Pump speed: 585 RPM
- Free air delivery: 35.0 CFM @ 0 PSI
- Delivery at 175 PSI: 28.1 CFM
- Tapered roller bearings: Both ends of crankshaft
- Precision steel connecting rods: Automotive-type insert bearings throughout
- Disc and spring valves: Serviceable, efficient, reliable
- 4-ring pistons: Better sealing, reduced oil carryover
- Centrifugal unloader: Loadless startup every cycle
Technical Specifications
- Model: I7312HC2-S
- Horsepower: 7.5 HP
- Phase: Three-phase (3-phase)
- Tank capacity: 120 gallons
- Tank type: Horizontal (HC)
- Pump RPM: 585
- Free air delivery (CFM @ 0 PSI): 35.0 CFM
- Delivery at working pressure (CFM @ 175 PSI): 28.1 CFM
- Maximum working pressure: 175 PSI
- Dimensions (L x W x H): 69 x 24 x 50 inches
- Weight: 820 lbs
- Aftercooler: Factory-mounted beltguard aftercooler included (#BGAC1M, 35 CFM rated)
Available Configurations in the 7.5 HP Three-Phase Lineup
- I738HC1-S — 7.5 HP, 3-phase, 80-gal horizontal, 895 RPM, 32.4/24.8 CFM, 64x20x48 in., 625 lbs
- I738HC2-S — 7.5 HP, 3-phase, 80-gal horizontal, 585 RPM, 35.0/28.1 CFM, 64x20x46 in., 730 lbs
- I7312HC2-S (this unit) — 7.5 HP, 3-phase, 120-gal horizontal, 585 RPM, 35.0/28.1 CFM, 69x24x50 in., 820 lbs
- I7312VC2-S — Same specs, vertical 120-gal tank, 44x30x75 in., 820 lbs
When Does a Shop Need This vs. Stepping Up or Down?
Choose the I7312HC2-S if: You have three-phase power, need a horizontal tank, and want maximum stored air in the 7.5 HP class. The 120-gallon tank covers shops running multiple technicians or spray booth operations where tank recovery time matters.
Step down to I738HC2-S if: Your air demand fits within the 80-gallon buffer — smaller footprint and 90 lbs lighter.
Step up to 10 HP three-phase if: Peak demand regularly exceeds 28.1 CFM at 175 PSI.
Factory Options Available
- Low Oil Control (#6304M): Automatic shutdown on low oil
- Hour Meter (#HRM460M or #HRM75M): Runtime tracking for maintenance scheduling
- Air Operated Auto Drain (#ADVSM): Automatic tank condensate drain
- Electronic Auto Drain (#SDV03M): Timer-based drain valve
- Dual Control (#DC2): Start/stop and constant speed modes
- Intake Noise Silencers (#SA100x2M for C2): Reduces inlet noise
- Belt Tensioner (#215DM): Simplifies belt adjustment
- Vibration Pads (#VP1004): Four 4x4x1 inch isolation pads
- Right from the Start Kit (#RFS002): Startup accessories bundle
Why Buy From Air Compressor Factory Direct?
We carry the full Castair industrial series in both single-phase and three-phase configurations. If you are upgrading from a single-phase unit and your shop now has three-phase service, we can help you confirm the voltage configuration (208/230/460V) before you order. Free shipping on qualifying orders. Free tech support before and after the sale. Full manufacturer warranty on every Castair industrial unit.
Call 866-217-0063 for quick answers and help!
