The Castair I733HC2-S is a 7.5 HP, 3-phase industrial air compressor on a 30-gallon horizontal ASME tank, equipped with the larger C2 pump and a factory-mounted magnetic motor starter. Where the I733HC1-S runs the C1 pump at 895 RPM and delivers 24.8 CFM at 175 PSI, the I733HC2-S steps up to the C2 pump running at 585 RPM — producing 35.0 CFM at 0 PSI and 28.1 CFM at 175 PSI. That extra CFM capacity is the main reason to choose the C2 variant over the C1, especially if your shop has higher sustained air demand but still wants the compact 30-gallon horizontal tank footprint.
The C2 pump is a two-stage, four-cylinder V4 cast iron unit. It runs slower than the C1 (585 vs. 895 RPM), which keeps operating temperatures lower and extends pump life further. Both pumps are all cast iron — no aluminum pump heads to warp under heat — and both are belt-driven from the 1,725 RPM industrial motor down to their rated pump speed.
C1 vs. C2 Pump — Which One Do You Actually Need?
This is the key decision in the I733 lineup. Here's how to think about it:
- C1 pump (I733HC1-S): 895 RPM, 24.8 CFM@175PSI — handles two to three air tools simultaneously, good for general shop work: impacts, ratchets, blow guns, tire inflators
- C2 pump (I733HC2-S, this unit): 585 RPM, 28.1 CFM@175PSI — adds about 3.3 CFM at working pressure, which matters when you're running heavier tools like DA sanders, air chisels, or a spray gun alongside other tools
- Slower RPM of the C2: 585 vs. 895 RPM means the C2 runs even cooler and quieter than the C1 — the tradeoff for the larger pump is a heavier unit
Pump Features — Cast Iron C2 Two-Stage V4
- All cast iron V4 cylinder configuration: Four cylinders in a V arrangement — more displacement per revolution than the C1 inline-2, producing higher CFM at lower RPM
- Slow 585 RPM operation: Even cooler and quieter than the C1 due to the lower shaft speed and larger flywheel
- Tapered roller bearings at both crankshaft ends: Superior support under belt-drive side loads and sustained two-stage compression
- Precision steel connecting rods: Automotive-type insert bearings at crankshaft, needle bearings at wrist pin
- Disc and spring valves: Easy to service, reliable under continuous duty cycling
- 4-ring pistons: Reduced oil carry-over into the discharge air stream
- Centrifugal unloader: No-load start on every cycle — protects motor and pump from high-inertia starts under pressure
Tank and Frame Features
- 30-gallon horizontal ASME-rated tank: Powder coated, channel-supported — same footprint as the HC1 variant
- ASME safety valve: Factory installed and rated for working pressure
- Metal belt guard: Fully enclosed, OSHA-compliant
- Copper discharge and unloader tube: Better heat dissipation than rubber or plastic lines
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 — ready to connect to your electrical service
- 3-phase operation: Smooth starts, lower peak current draw, longer motor life than single-phase equivalents
What's in the Box
- Castair I733HC2-S compressor assembly (C2 pump, motor, 30-gal horizontal 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
- I733HC1-S: 7.5HP, 3-phase, 30-gal horizontal, C1 pump, 895 RPM, 24.8 CFM@175PSI, magnetic starter
- I733HC2-S (this unit): 7.5HP, 3-phase, 30-gal horizontal, C2 pump, 585 RPM, 28.1 CFM@175PSI, magnetic starter
- I738HC1-S: 7.5HP, 3-phase, 80-gal horizontal, C1 pump, 895 RPM, 24.8 CFM@175PSI — 64x20x48 in., 625 lbs
- I738HC2-S: 7.5HP, 3-phase, 80-gal horizontal, C2 pump, 585 RPM, 28.1 CFM@175PSI — 64x20x46 in., 730 lbs
- I7312HC2-S: 7.5HP, 3-phase, 120-gal horizontal, C2 pump — maximum reserve capacity
When Does a Shop Need This vs. Stepping Up or Down
Choose the I733HC2-S when you need more CFM than the C1 delivers but still want the compact 30-gallon horizontal tank. The extra 3.3 CFM at working pressure is meaningful for shops running DA polishers, spray guns, or heavier hand tools alongside conventional impact and ratchet work.
Step up to I738HC2-S if you need both the higher CFM of the C2 pump AND more air reserve — the 80-gallon tank gives you longer duty cycles between compressor runs. If you're painting cars or doing sustained sandblasting, the 80-gallon tank is the better call.
Step down to I733HC1-S if your shop's sustained demand is lower — general automotive service with impacts, ratchets, and tire work doesn't always need the C2's extra CFM, and the C1 is a lighter, simpler unit.
Technical Specifications
- Model: I733HC2-S
- Horsepower: 7.5 HP
- Phase: 3-phase
- Tank Capacity: 30 gallons
- Tank Type: Horizontal, ASME-rated, powder coated
- 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
- Pump Stage: Two-stage
- Pump Cylinder Configuration: V4
- Starter: Factory-mounted magnetic motor starter included
- Discharge Tube: Copper
- Belt Guard: Metal, fully enclosed
Why Buy From Air Compressor Factory Direct?
We've specialized in industrial and commercial air compressors since 2016. When you call, you're talking to someone who can explain why the C2 pump's lower RPM matters for your shop's longevity expectations, whether 30 gallons is enough reserve for your tools, and what electrical service you'll need to run this unit. Free shipping, free tech support at 866-217-0063, and the full Castair manufacturer warranty. Call us before you buy if you're comparing configurations.
Call 866-217-0063 for quick answers and help!
