Castair 7.5 HP 3-Phase Rotary Screw Air Compressor — Horizontal Tank, 230V (R738HP75-230)
The Castair R738HP75-230 is a 7.5 HP, 3-phase, 100% duty cycle rotary screw air compressor mounted on an 80-gallon horizontal ASME tank, wired for 230V. If you are running a busy auto shop, body shop, or light industrial operation and you are tired of a piston compressor cycling on and off all day, this is the class of machine you step up to. Rotary screw compressors run continuously without heat cycling. The R738HP75-230 delivers 31 CFM at 100 PSI around the clock. The 80-gallon horizontal tank keeps your floor footprint manageable at 64 x 32 x 44 inches while giving you buffer capacity for tools that pulse demand. Standard pressure is 135 PSI, with factory options for 150 or 175 PSI.
Why Rotary Screw vs. Piston at 7.5 HP?
A 7.5 HP piston compressor is rated for 50 to 60 percent duty cycle at best. Run a spray gun, a continuous grinder, or multiple air tools simultaneously and you will hear that piston motor cycling constantly, running hot, and wearing out faster. The R738HP75-230 is rated for 100% duty cycle — full continuous operation. It produces 31 CFM at 100 PSI without stopping. The air end runs on a heavy-duty industrial 1725 RPM motor, and the entire system is built around off-the-shelf components so your local supplier can source parts without waiting on proprietary orders.
Air End and Drive System
- Duty cycle: 100% — continuous operation rated
- Air end: Rotary screw, single solenoid control — no computers, no lockout codes
- Motor: Heavy-duty industrial 1725 RPM with full 15% service factor or higher
- Drive: Off-shelf V-belts with adjustable belt tightener — tension without removing belt guards
- Lubrication: Factory-filled with 4,000-hour / 1-year synthetic CAST-LUBE oil
- Oil filter: Spin-on automotive-type oil filter
- Air filter: Automotive-style paper element air filter
Controls and Safety
- Pressure control: Single solenoid operates the air end — no PLC or computer logic involved
- Gauges: Easy-read pressure and temperature gauges standard
- High pressure shutdown: Standard
- Dual high temperature shutdown: Standard
- 10-minute shutdown timer: Standard — shuts down automatically when air demand stops, cuts electricity cost
- No lockout codes: Unlike many competing brands, this unit will not lock you out and require a dealer reset
Tank and Cooling
- Tank capacity: 80 gallons, horizontal configuration
- Tank certification: USA-made ASME-certified steel tank
- Air/oil separator: Built-in with spin-on filter element
- Aftercooler: Air-cooled aftercooler and oil cooler standard — easily removed for cleaning
- Plumbing: Off-shelf copper piping for all air/oil lines — field-serviceable anywhere
Electrical
- Voltage: 230V, 3-phase
- Starter: Name-brand magnetic starter and controls, factory mounted and wired — connect incoming power and run
- 460V option: Same machine available as R738HP75-460 for 460V 3-phase service
Maintenance
- Hour meter: Standard — makes scheduling oil changes and filter replacements straightforward
- Oil changes: Spin-on oil filter, spin-on air/oil separator filter — no special tools needed
- Belt service: Off-shelf V-belts with adjustable tensioner — quick to replace in the field
- Aftercooler cleaning: Easily removed without major disassembly
- PM kit: MKD3-4 kit covers D3, D31, and D4 air ends (5-10 HP range) — includes 2 air filters, 4 oil filters, 1 separator filter, 5 gallons synthetic oil, saves 10% vs. individual purchases
What Is in the Box
- Castair R738HP75-230 rotary screw compressor unit, fully assembled
- 80-gallon horizontal ASME tank (USA-made)
- Air-cooled aftercooler and oil cooler
- Magnetic starter and controls, factory wired
- Hour meter
- Pressure and temperature gauges
- Factory fill of CAST-LUBE 4,000-hour synthetic oil
Vibration pads (VP1004, set of 4), ball valve, and metal flex hose are recommended accessories — available factory-mounted or sold separately.
Available Configurations and Upgrade Path
- R538HP75 — 5 HP, 3-phase, 80 gal horizontal, 20 CFM, 64x32x44, 470 lbs
- R738HP75-230 (this unit) — 7.5 HP, 3-phase, 230V, 80 gal horizontal, 31 CFM, 64x32x44, 546 lbs
- R738HP75-460 — Same as above, 460V 3-phase
- R738VP75-230 — Same 7.5 HP specs, vertical tank, 34x26x70, 546 lbs — smaller floor footprint
- R1038HP75 — 10 HP, 3-phase, 80 gal horizontal, 40 CFM, 64x32x44, 585 lbs
- R15312HP75 — 15 HP, 3-phase, 120 gal horizontal, 52 CFM, 69x33x55, 765 lbs
Pressure options available at order: 135 PSI (standard), 150 PSI, or 175 PSI.
When Does a Shop Need This vs. Stepping Up or Down?
This machine fits your shop if: You have 3-phase 230V service, need continuous CFM for 2-3 simultaneous air tools (impacts, ratchets, HVLP guns), and want the horizontal layout for low-ceiling or space-constrained bays. The 31 CFM at 100 PSI handles most mid-size shop workflows without bottlenecking.
Step up to 10 HP (R1038HP75) if: You are running more than three continuous air tools, a large spray booth, or a tire shop with back-to-back impact use. The 10 HP delivers 40 CFM at 100 PSI.
Step down to 5 HP (R538HP75) if: You are a smaller single-tech shop with intermittent tool use — 20 CFM handles one-lift shops comfortably.
Verify your power supply first: This is a 3-phase 230V unit. Single-phase shops should look at the R718HP75. Shops with 460V 3-phase service should order the R738HP75-460.
Technical Specifications
- Model: R738HP75-230
- Horsepower: 7.5 HP
- Phase: 3-phase
- Voltage: 230V (460V available as R738HP75-460)
- CFM @ 100 PSI: 31
- Standard operating pressure: 135 PSI (150 or 175 PSI available)
- Duty cycle: 100%
- Tank size: 80 gallons, horizontal
- Tank certification: ASME (USA-made)
- Dimensions (LxWxH): 64" x 32" x 44"
- Weight: 546 lbs
- Motor speed: 1725 RPM
- Motor service factor: 15% or higher
- Oil: CAST-LUBE synthetic, 4,000-hour / 1-year service interval
- Warranty: 2 years on air end, electric motor, and tank
Why Buy From Air Compressor Factory Direct?
- Castair specialists: We carry the full line — compressors, dryers, filters, and parts
- Free shipping to commercial addresses
- Free tech support: Call 866-217-0063 — talk to someone who knows rotary screw compressors
- Full manufacturer warranty: 2-year warranty on air end, motor, and tank, honored without hassle
- Honest sizing guidance: If 7.5 HP is not the right size for your shop, we will tell you
Call 866-217-0063 for quick answers and help!
