Castair C518VC1 — 5HP Two-Stage Commercial Air Compressor, 80-Gallon Vertical Tank
The C518VC1 is Castair's 5HP two-stage commercial compressor on an 80-gallon vertical ASME tank. It runs at 715 RPM — very slow for a commercial compressor — delivers 21.7 CFM @ 0 PSI and 18.1 CFM @ 100 PSI, and is factory-set to 175 PSI shutoff. At 560 lbs and $2,229.55, this is the quiet, high-pressure, compact-footprint top of the commercial vertical lineup. No magnetic starter required at 230V/22A single-phase. Dimensions: 32 x 24 x 74 inches.
Confirmed Specifications — From Castair's Published Data
- Model: C518VC1
- Horsepower: 5HP
- Compression Stages: Two-stage
- Tank: 80-gallon vertical, ASME-rated
- Pump RPM: 715
- CFM @ 0 PSI: 21.7
- CFM @ 100 PSI: 18.1
- Dimensions (LxWxH): 32 x 24 x 74 inches
- Voltage/Amps: 230V / 22A (single-phase)
- Shipped Weight: 560 lbs
- Shutoff Pressure: 175 PSI (two-stage)
- Magnetic Starter Required: No
Two-Stage Advantages at 5HP
The C518VC1 and the C518VA8 have almost identical CFM output — 18.1 vs. 18.3 at 100 PSI — but they're fundamentally different machines. The two-stage C518VC1 runs 34% slower (715 RPM vs. 1,088 RPM), shuts off at 175 PSI instead of 125 PSI, and weighs 125 lbs more. That weight comes from a more substantial pump construction:
- Tapered roller bearings at both crankshaft ends (vs. ball bearings in single-stage)
- Mechanical centrifugal unloader (vs. bleeder switch in single-stage)
- More complex valve train for two-stage compression
- Additional cylinder for high-pressure stage
The result is a compressor that runs quieter, handles higher working pressure, and is built for longer service life between maintenance intervals.
Two-Stage Pump Features
- All cast iron: Cylinders, heads, crankcase
- Two compression stages: 175 PSI factory shutoff
- 715 RPM pump speed: Significantly quieter than single-stage commercial units
- Tapered roller bearings: Both crankshaft ends — superior to ball bearings under sustained load
- Centrifugal unloader: Fully load-less motor starts — not just a bleeder valve
- Disc and spring valves: Easy service, reliable
- 4-ring pistons: Better sealing, less oil carry-over
- Precision steel connecting rods: Automotive-type insert bearings at crank, needle at wrist pin
80-Gallon Vertical ASME Tank
- Footprint: 32 x 24 inches at base — same as the C518VA8
- Height: 74 inches — 8 inches taller than the single-stage C518VA8 due to the larger two-stage pump assembly
- ASME-rated: Code-compliant pressure vessel
- Powder coat finish: Rust-resistant
- 4-leg elevated base: Standard on Castair verticals
- Copper discharge tube: Better heat dissipation than rubber hose
- Rigid metal belt guard: OSHA-compliant
When to Choose the C518VC1 Over the C518VA8
Choose C518VC1 (two-stage) when:
- You use spray equipment, sand blast cabinets, plasma cutters, or other tools that benefit from higher tank pressure (175 PSI reserve means more working pressure when demand is high)
- Noise matters — a shop working in or near an office, retail area, or noise-sensitive environment will appreciate the difference between 715 and 1,088 RPM under load
- You want the pump to last as long as possible under daily commercial use
The single-stage C518VA8 is adequate when: Your tools max out at 90-100 PSI, your shop tolerates compressor noise, and the $228 price premium for two-stage is a consideration.
Factory Options
- Auto Drain (#ADVSM or #SDV03M): Automatic condensate drain
- Silencer 1" (#SA100M): Further reduces pump intake noise
- Belt Guard Aftercooler (#BGAC1M): 35 CFM — reduces moisture in compressed air
- Vibration Pads (#VP1004): 4x4x1" rubber isolation pads (set of 4)
- Right From the Start Kit (#RFS001): Break-in oil, pads, ball valve, flex hose, filter element
What's in the Box
- Assembled compressor (two-stage pump, motor, 80-gallon vertical tank, belt drive)
- Rigid metal belt guard (totally enclosed)
- Copper discharge and unloader tube
- ASME safety valve and pressure switch
- Oil sight glass and automotive-type air filter/silencer
- Not included: Compressor oil, vibration pads, flex hose for shop piping connection
Why Buy From Air Compressor Factory Direct?
We carry the full Castair commercial lineup and can help you evaluate single-stage vs. two-stage tradeoffs for your specific shop environment. Free shipping. Free tech support at 866-217-0063. Full manufacturer warranty. We've been doing this since 2016 and we'll give you a straight answer on which unit fits your use case.
Call 866-217-0063 for quick answers and help!
