The Castair I733HC1-S is a 7.5 HP, 3-phase industrial air compressor built on a 30-gallon horizontal ASME tank with a factory-mounted magnetic motor starter. This is the smallest horizontal tank configuration in Castair's 7.5HP 3-phase industrial lineup — designed for shops that need genuine industrial-grade cast iron performance in a tighter footprint or where floor space constraints make the 80-gallon horizontal impractical. If you're running a 3-phase service drop and want a ready-to-wire unit with overload protection already mounted, the -S suffix tells you the magnetic starter is included at the factory.
This compressor uses the Castair C1 pump — a two-stage cast iron unit running at 895 RPM. At that speed, the pump turns slowly enough that heat stays manageable, wear is minimal, and you can expect a long service life without major overhauls. The C1 pump uses an inline-2 cylinder configuration and is rated at 32.4 CFM at 0 PSI, delivering 24.8 CFM at 175 PSI working pressure. For a shop running air ratchets, impact wrenches, blow guns, and tire equipment simultaneously, that's a solid supply figure.
Why 3-Phase Matters for Shop Compressors
If your building has 3-phase power, running a single-phase compressor is leaving efficiency and longevity on the table. Three-phase motors start smoother, run cooler, draw lower peak current, and last longer than equivalent single-phase motors under continuous shop use. The I733HC1-S is wired for 3-phase from the factory — the magnetic motor starter handles the overload protection and gives you a proper disconnect point. No single-phase conversion required, no add-on starter to source separately.
Pump Features — Cast Iron C1 Two-Stage
- All cast iron construction: Cylinders, heads, and crankcase are cast iron throughout — no aluminum hot spots, no warped pump heads under sustained load
- Slow 895 RPM operation: The C1 pump runs at 895 RPM with this motor combination, compared to 1,725 RPM on a typical direct-drive compressor. Slower speed means lower heat, less wear, and a much longer pump life
- Tapered roller bearings at both crankshaft ends: Handles radial and thrust loads better than ball bearings, especially under the belt-drive side load
- Precision steel connecting rods: Automotive-type rod insert bearings at crankshaft, needle bearings at wrist pin — not stamped sheet metal hardware
- Disc and spring valves: Easy to service, more efficient than reed valves, and more reliable under sustained pressure cycling
- 4-ring pistons: Better ring seal means less oil carry-over into the discharge air and cleaner air to your tools
- Centrifugal unloader: Every start is a no-load start — the unloader releases head pressure before the motor torques up, protecting both motor and pump on every cycle
Tank and Frame Features
- 30-gallon horizontal ASME-rated tank: Powder coated, channel-supported horizontal configuration for stable floor mounting
- ASME safety valve: Factory installed, rated for the working pressure of the system
- Metal belt guard: Fully enclosed, not a plastic clip-on — meets OSHA guarding requirements
- Copper discharge and unloader tube: Copper handles heat dissipation better than rubber or plastic alternatives and won't crack from oil or pressure cycling
Motor and Electrical
- 1,725 RPM heavy-duty industrial motor: Full 15% service factor or higher — built to run at rated load continuously without overheating
- Factory-mounted magnetic motor starter: 3-phase overload protection installed at the factory, wired and ready — eliminates the need to source and mount a separate starter
- 3-phase operation: Lower starting current, smoother operation, and better motor longevity compared to single-phase in a shop environment
What's in the Box
- Castair I733HC1-S compressor assembly (pump, motor, tank, belt drive, belt guard)
- Factory-mounted magnetic motor starter (3-phase, sized for 7.5HP)
- ASME safety valve (installed)
- Copper discharge and unloader tube (installed)
- Pressure switch (installed)
Available Configurations — 7.5HP 3-Phase Industrial Lineup
Castair builds the 7.5HP 3-phase lineup in several tank configurations. Understanding where the I733HC1-S sits helps you pick the right one:
- I733HC1-S (this unit): 7.5HP, 3-phase, 30-gal horizontal, C1 pump, 895 RPM, 32.4 CFM@0PSI / 24.8 CFM@175PSI — smallest horizontal tank in this HP class, with magnetic starter
- I738HC1-S: Same HP and pump, 80-gallon horizontal tank — more reserve volume for tools with higher burst demand, dimensions 64x20x48 in., 625 lbs
- I738HC2-S: 7.5HP, 3-phase, 80-gal horizontal, C2 pump (585 RPM), 35.0 CFM@0PSI / 28.1 CFM@175PSI — higher CFM output with the larger C2 pump
- I738VC1-S: 7.5HP, 3-phase, 80-gal vertical, C1 pump — same output as HC1, vertical tank for smaller floor footprint, dimensions 32x24x74 in., 625 lbs
- I7312HC2-S: 7.5HP, 3-phase, 120-gal horizontal, C2 pump — maximum reserve for high-demand shops
When Does a Shop Need This vs. Stepping Up or Down
The I733HC1-S is right for you if: You have 3-phase power, want an industrial-grade compressor in a compact horizontal package (secondary compressor, limited floor space situation), and need the magnetic starter already mounted so you can connect power and start working. The 30-gallon tank with 24.8 CFM at 175 PSI supports multiple hand tools running simultaneously in a moderate-demand shop.
Step up to the I738HC1-S if you have the floor space and want more air reserve — the 80-gallon tank means longer intervals between compressor cycles, which matters for sustained operations like spray painting or sandblasting.
Step up to the HC2 variants (C2 pump) if you need higher CFM. The C2 pump at 585 RPM delivers 28.1 CFM at 175 PSI vs. 24.8 CFM from the C1 — meaningful when running high-demand tools or multiple bays simultaneously.
Step down to a commercial/garage series if you don't have 3-phase power or the industrial pump construction is more than your duty cycle requires.
Technical Specifications
- Model: I733HC1-S
- Horsepower: 7.5 HP
- Phase: 3-phase
- Tank Capacity: 30 gallons
- Tank Type: Horizontal, ASME-rated, powder coated
- Pump Model: C1 (two-stage, cast iron)
- Pump RPM: 895
- CFM @ 0 PSI: 32.4
- CFM @ 175 PSI: 24.8
- Max Working Pressure: 175 PSI
- Motor Speed: 1,725 RPM
- Pump Stage: Two-stage
- Pump Cylinder Configuration: Inline 2
- 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. When you call us, you're talking to someone who knows the difference between a C1 and C2 pump, can explain whether a 30-gallon or 80-gallon tank fits your shop's duty cycle, and can help you spec the right configuration for your electrical service. We've been at this since 2016. Free shipping on this unit, free technical support, and the full Castair manufacturer warranty. If you're deciding between configurations, call us — honest guidance, not a sales pitch.
Call 866-217-0063 for quick answers and help!
