The Castair I738HC2-S is a 7.5 HP, 3-phase industrial air compressor on an 80-gallon horizontal ASME tank with the C2 pump and a factory-mounted magnetic motor starter. The C2 pump runs at 585 RPM and delivers 35.0 CFM at 0 PSI and 28.1 CFM at 175 PSI — that's 3.3 more CFM at working pressure than the C1 pump in the I738HC1-S. If your shop runs spray guns, DA sanders, air chisels, or supports three bays simultaneously, the C2's extra output is what you're buying here. Dimensions are 64x20x46 inches, shipped weight 730 lbs.
The C2 is a V4 configuration — four cylinders in a V arrangement — running at a lower shaft speed than the C1's inline-2. The result is a pump that produces more air while running cooler and quieter. The tradeoff is weight: the C2 unit ships at 730 lbs vs. 625 lbs for the C1 version. For most shops making this choice, the extra CFM is worth it.
C1 vs. C2 Pump — Deciding Factor at 7.5HP
Both pumps are two-stage cast iron units belt-driven from the same 1,725 RPM industrial motor. Here's the difference:
- C1 pump (I738HC1-S): 895 RPM, 24.8 CFM@175PSI, 625 lbs shipped — handles 2-3 air tools simultaneously for general shop work
- C2 pump (I738HC2-S, this unit): 585 RPM, 28.1 CFM@175PSI, 730 lbs shipped — handles heavier sustained demand, spray guns, DA polishers, multi-bay operations
- C2 runs cooler: Lower RPM means less heat per hour of operation — when you're running 8 hours a day, that temperature difference adds up in pump longevity
Pump Features — Cast Iron C2 Two-Stage V4
- All cast iron V4 cylinder configuration: Four cylinders in a V arrangement — higher displacement than the C1, producing more CFM at lower RPM
- Slow 585 RPM operation: Lower shaft speed means less heat and less wear than faster-turning pump designs
- Tapered roller bearings at both crankshaft ends: Superior support for the larger pump's loads under belt drive and two-stage compression
- Precision steel connecting rods: Automotive-type 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
- Centrifugal unloader: No-load start every time, protecting motor and pump
Tank and Frame Features
- 80-gallon horizontal ASME-rated tank: Powder coated, channel-supported base for stable floor installation
- ASME safety valve: Factory installed, rated for working pressure
- Metal belt guard: Fully enclosed — not a plastic clip-on
- 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 or higher — continuous duty rated
- Factory-mounted magnetic motor starter: 3-phase overload protection installed and wired at the factory — ready to connect to your electrical panel
- 3-phase operation: Smooth starts, lower peak current draw, longer motor life vs. single-phase
What's in the Box
- Castair I738HC2-S compressor assembly (C2 pump, motor, 80-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
- I738HC1-S: 7.5HP, 3-phase, 80-gal horizontal, C1 pump, 895 RPM, 24.8 CFM@175PSI, 64x20x48 in., 625 lbs, magnetic starter included
- I738HC1: Same as above without factory-mounted magnetic starter
- I738HC2-S: 7.5HP, 3-phase, 80-gal horizontal, C2 pump, 585 RPM, 28.1 CFM@175PSI, 64x20x46 in., 730 lbs, magnetic starter included
- I738HC2: Same as above without factory-mounted magnetic starter
- I738VC1-S: 7.5HP, 3-phase, 80-gal vertical, C1 pump, 895 RPM, 24.8 CFM@175PSI, 32x24x74 in., 625 lbs, magnetic starter included
- I738VC1: Same as above without factory-mounted magnetic starter
- I738VC2-S: 7.5HP, 3-phase, 80-gal vertical, C2 pump, 585 RPM, 28.1 CFM@175PSI, 40x24x74 in., 730 lbs, magnetic starter included
- I738VC2: Same as above without factory-mounted magnetic starter
- 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 I738HC2-S is right for your shop if: You have 3-phase power, need the higher CFM output of the C2 pump (28.1 CFM@175PSI), and want an 80-gallon tank for adequate reserve. This is the go-to unit for shops running spray guns, DA polishers, or three-bay operations alongside general hand tools. The C2 pump at 585 RPM runs quieter and cooler than the C1 at 895 RPM.
Step down to I738HC1-S if your shop's sustained air demand is lower — general automotive service with impacts and ratchets doesn't always need the C2's extra CFM, and the C1 is a lighter, simpler unit.
Step up to I7312HC2-S (120-gallon) for maximum reserve — if you're painting multiple vehicles per day or running continuous sandblasting, the 120-gallon tank keeps the compressor from short-cycling.
Technical Specifications
- Model: I738HC2-S
- Horsepower: 7.5 HP
- Phase: 3-phase
- Tank Capacity: 80 gallons
- Tank Type: Horizontal, ASME-rated, powder coated
- Tank Dimensions: 64 x 20 x 46 in. (L x W x H)
- Shipping Weight: 730 lbs
- 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
- Magnetic Starter (208/230V): S72 with B36 heaters
- Magnetic Starter (460V): S74 with B22 heaters
- 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 at it since 2016. When you call, you're talking to someone who knows the Castair lineup, can tell you whether the C1 or C2 pump fits your shop's CFM requirements, and can help you decide between horizontal and vertical tank configurations for your space. Free shipping, free technical support at 866-217-0063, full Castair manufacturer warranty. Call us before you buy if you have questions about which configuration is right for your shop.
Call 866-217-0063 for quick answers and help!
