The Castair I73CUC2-S is a 7.5 HP, 3-phase industrial air compressor in a cube (tankless) configuration with the C2 pump and a factory-mounted magnetic motor starter. The C2 pump runs at 585 RPM and produces 35.0 CFM at 0 PSI and 28.1 CFM at 175 PSI — that's the highest CFM output in the 7.5HP 3-phase cube lineup. Like the I73CUC1-S, this unit ships without a receiver tank, making it the right choice for installations where a separate ASME tank is already in place or being specified independently.
The C2 is a V4 four-cylinder cast iron pump — four cylinders in a V arrangement — running at a lower shaft speed than the C1's 895 RPM. The lower RPM produces less heat per operating hour and more air per revolution. For a high-demand shop that needs maximum CFM from a 7.5HP motor but is doing a custom or central-plant installation, the I73CUC2-S delivers the most airflow in this format.
C1 vs. C2 Cube Pump — Which Do You Need
- I73CUC1-S (C1 pump): 895 RPM, 24.8 CFM@175PSI — handles general shop demand, 2-3 air tools simultaneously
- I73CUC2-S (C2 pump, this unit): 585 RPM, 28.1 CFM@175PSI — handles heavier demand, spray guns, DA tools, or multi-tool use
- Price difference: The C2 unit runs approximately $691 more than the C1 — compare whether your shop's sustained tool demand justifies the higher CFM before ordering
Pump Features — Cast Iron C2 Two-Stage V4
- All cast iron V4 cylinder configuration: Four cylinders in a V arrangement — more displacement than the C1 inline-2, producing higher CFM at lower shaft speed
- Slow 585 RPM operation: Lower heat per hour, reduced wear, quieter operation than faster-turning pump designs
- Tapered roller bearings at both crankshaft ends: Handles the higher loads of the larger V4 pump under sustained two-stage compression
- Precision steel connecting rods: Automotive-type rod insert bearings at crankshaft, needle bearings at wrist pin
- Disc and spring valves: Field-serviceable, reliable under continuous duty cycling
- 4-ring pistons: Less oil carry-over into the discharge air stream
- Centrifugal unloader: No-load start every cycle — head pressure releases before the motor cranks up
Motor and Electrical
- 1,725 RPM heavy-duty industrial motor: Full 15% service factor — continuous duty rated
- Factory-mounted magnetic motor starter: 3-phase overload protection, wired at the factory
- 3-phase operation: Smooth starts, lower peak current draw, better motor longevity vs. single-phase
What's in the Box
- Castair I73CUC2-S cube compressor assembly (C2 pump, motor, base/cube frame, belt drive, belt guard)
- Factory-mounted magnetic motor starter (3-phase, sized for 7.5HP)
- Copper discharge and unloader tube (installed)
- Pressure switch (installed)
- Tank not included — this is a tankless cube pump unit
Available Configurations
- I73CUC1-S: 7.5HP, 3-phase, cube (tankless), C1 pump, 895 RPM, 24.8 CFM@175PSI, magnetic starter
- I73CUC2-S (this unit): 7.5HP, 3-phase, cube (tankless), C2 pump, 585 RPM, 28.1 CFM@175PSI, magnetic starter
- I738HC2-S: Same C2 pump and motor, plus 80-gal horizontal ASME tank — 64x20x46 in., 730 lbs, complete unit
- I738VC2-S: Same C2 pump and motor, plus 80-gal vertical ASME tank — 40x24x74 in., 730 lbs, complete unit
When Does a Shop Need This vs. Stepping Up or Down
Choose the I73CUC2-S when you need the maximum CFM of the C2 pump in a cube/tankless configuration for a custom industrial installation, replacement job, or central-plant setup. At 28.1 CFM at 175 PSI, this unit can handle spray guns, DA polishers, and multi-tool shop environments when paired with an appropriately sized receiver tank.
Choose I73CUC1-S instead if your shop's air demand is satisfied by 24.8 CFM at 175 PSI — the C1 cube unit is approximately $691 less and covers most general automotive service needs.
Buy a full unit (I738HC2-S or I738VC2-S) if you need the complete compressor including the tank. The cube configuration is specifically for situations where the tank is handled separately.
Technical Specifications
- Model: I73CUC2-S
- Horsepower: 7.5 HP
- Phase: 3-phase
- Configuration: Cube / Tankless
- Tank: Not included
- Pump Model: C2 (two-stage, cast iron, V4)
- Pump RPM: 585
- CFM @ 0 PSI: 35.0
- CFM @ 175 PSI: 28.1
- Max Working Pressure: 175 PSI
- Motor Speed: 1,725 RPM
- Starter: Factory-mounted magnetic motor starter included
- Discharge Tube: Copper
- Belt Guard: Metal, fully enclosed
Why Buy From Air Compressor Factory Direct?
We specialize in industrial and commercial air compressors and have been matching shops to the right equipment since 2016. When you call us, you're talking to someone who knows the Castair lineup — pump models, tank options, starter requirements, CFM calculations for your tool mix. Free shipping, free technical support at 866-217-0063, and the full Castair manufacturer warranty. If you're comparing cube pump configurations or deciding between the C1 and C2, call us.
Call 866-217-0063 for quick answers and help!
