The Castair I738HC1-S is a 7.5 HP, 3-phase industrial air compressor mounted on an 80-gallon horizontal ASME tank, with a factory-mounted magnetic motor starter. This is the core heavy-duty shop compressor in Castair's 7.5HP 3-phase horizontal lineup — 80 gallons of reserve air, the two-stage C1 cast iron pump running at 895 RPM, and 24.8 CFM at 175 PSI. At 64 inches long, 20 inches wide, and 48 inches tall, it fits along a shop wall without dominating the floor. Shipped weight is 625 lbs.
The -S suffix means the magnetic motor starter is factory-mounted and wired — you bring 3-phase power to the panel and go. Castair sizes the starter heater for the motor at the factory. For a 7.5HP 3-phase unit at 208/230V, that's the S72 starter with B36 heaters. At 460V it's the S74 with B22 heaters. No field sourcing required.
Why the 80-Gallon Horizontal Tank
The tank size determines how often the compressor cycles and how much burst air you have available for high-demand tools. An 80-gallon tank at 175 PSI holds substantially more reserve than a 30-gallon tank — meaning your compressor runs less often, the motor starts fewer times per hour, and tools don't starve during a burst demand. For a shop running two to three bays with air impacts, ratchets, and tire equipment, the 80-gallon tank is the right balance between reserve volume and footprint.
Pump Features — Cast Iron C1 Two-Stage
- All cast iron construction: Cylinders, heads, and crankcase — cast iron throughout, not aluminum
- Slow 895 RPM operation: Belt-drive reduction from the 1,725 RPM motor keeps heat low and pump life long
- Tapered roller bearings at both crankshaft ends: Handles radial and thrust loads better than ball bearings under continuous service
- Precision steel connecting rods: Automotive-type rod insert bearings at crankshaft, needle bearings at wrist pin
- Disc and spring valves: Easy to service, reliable under sustained pressure cycling
- 4-ring pistons: Reduced oil carry-over into the discharge air
- Centrifugal unloader: No-load start on every cycle — head pressure releases before the motor cranks up
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 I738HC1-S compressor assembly (C1 pump, motor, 80-gal horizontal tank, belt drive, belt guard)
- Factory-mounted magnetic motor starter (3-phase, sized for 7.5HP at your voltage)
- 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 I738HC1-S is right for your shop if: You have 3-phase power, your shop runs general automotive service — impacts, ratchets, tire equipment, blow guns — and you want an 80-gallon reserve so the compressor isn't cycling constantly throughout the day. The 24.8 CFM at 175 PSI handles two to three air tools simultaneously without starving them.
Step up to I738HC2-S if you need more CFM — 28.1 vs. 24.8 at 175 PSI. The C2 pump's extra output matters when you're running DA sanders, spray guns, air chisels, or multiple bays simultaneously. The C2 also runs at a lower 585 RPM, which is quieter and produces less heat per hour of operation.
Step up to I7312HC2-S (120-gallon) if your shop runs sustained operations like production spray painting, sandblasting, or line work where the compressor needs maximum reserve to prevent short-cycling on heavy tools.
Consider I738VC1-S if your floor space is tighter and you can use vertical height instead of horizontal floor area.
Technical Specifications
- Model: I738HC1-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 48 in. (L x W x H)
- Shipping Weight: 625 lbs
- Pump Model: C1 (two-stage, cast iron, inline-2)
- Pump RPM: 895
- CFM @ 0 PSI: 32.4
- CFM @ 175 PSI: 24.8
- 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!
