Castair C518HC1 — 5HP Two-Stage Commercial Air Compressor, 80-Gallon Horizontal Tank
The C518HC1 is Castair's 5HP two-stage commercial air compressor on an 80-gallon horizontal ASME tank. It runs at a very slow 715 RPM, delivers 21.7 CFM @ 0 PSI and 18.1 CFM @ 100 PSI, and is factory-set to shut off at 175 PSI — 50 PSI higher than the single-stage commercial units. At 560 lbs and $2,561.05, this is the heavy, quiet, high-pressure 80-gallon option in Castair's commercial lineup. No magnetic starter required at 5HP/230V single-phase.
Confirmed Specifications — From Castair's Published Data
- Model: C518HC1
- Horsepower: 5HP
- Compression Stages: Two-stage
- Tank: 80-gallon horizontal, ASME-rated
- Pump RPM: 715
- CFM @ 0 PSI: 21.7
- CFM @ 100 PSI: 18.1
- Dimensions (LxWxH): 64 x 20 x 48 inches
- Voltage/Amps: 230V / 22A (single-phase)
- Shipped Weight: 560 lbs
- Shutoff Pressure: 175 PSI (two-stage)
- Magnetic Starter Required: No
Two-Stage vs. Single-Stage — The Real Difference
At the same 5HP and similar CFM numbers, the two-stage C518HC1 differs from the single-stage C518HA8 in three important ways:
- Working pressure: 175 PSI shutoff versus 125 PSI — the two-stage unit is the right choice for spray equipment, plasma cutting, or any application requiring higher working pressure
- Operating RPM: 715 versus 1,088 — the two-stage pump runs 34% slower, which means measurably quieter operation and longer pump life per hour of runtime
- Weight: 560 lbs versus 435 lbs — the two-stage pump is significantly heavier due to its construction (tapered roller bearings, additional pump cylinder, centrifugal unloader mechanism)
Two-Stage Pump Features — Commercial Series
Castair's two-stage commercial pumps add several features beyond the single-stage units:
- Two-stage compression: First stage compresses to intermediate pressure; second stage brings to 175 PSI — more thermally efficient at high pressure
- 715 RPM pump speed: Even slower than the single-stage commercial units — less heat, longer valve and bearing life
- Tapered roller bearings: Both ends of the crankshaft — superior to the ball bearings in single-stage units
- Mechanical centrifugal unloader: The two-stage units use a centrifugal unloader for load-less starts, not just a bleeder switch
- Precision steel connecting rods: Automotive-type rod insert bearings at crankshaft, needle bearings at wrist pin
- Disc and spring valves: Easy service access, high efficiency
- 4-ring pistons: Better sealing efficiency, less oil carry-over
- All cast iron construction: Cylinders, heads, crankcase
80-Gallon Horizontal ASME Tank
- Horizontal layout: 64 x 20-inch footprint, 48 inches tall — low profile for low-ceiling environments
- Note height difference: At 48 inches tall, this is 7 inches taller than the single-stage C518HA8 (41 inches) due to the larger two-stage pump assembly
- Powder-coated ASME pressure vessel: Code-compliant, rust-resistant
- Copper discharge and unloader tube: Better than rubber hose at the pump outlet
- Rigid metal belt guard: OSHA-compliant
80-Gallon Commercial Unit Comparison
| Model | Stage | Orientation | RPM | CFM@100 | Max PSI | Dimensions | Weight |
|---|---|---|---|---|---|---|---|
| C518VA8 | Single | Vertical | 1088 | 18.3 | 125 | 32x24x66" | 435 lbs |
| C518HA8 | Single | Horiz. | 1088 | 18.3 | 125 | 64x20x41" | 435 lbs |
| C518VC1 | Two | Vertical | 715 | 18.1 | 175 | 32x24x74" | 560 lbs |
| C518HC1 | Two | Horiz. | 715 | 18.1 | 175 | 64x20x48" | 560 lbs |
When Does a Shop Need Two-Stage?
You need the C518HC1 (two-stage) if:
- Your spray equipment, plasma cutter, or other tools require working pressure above 125 PSI
- Noise level is a concern — the 715 RPM two-stage pump is noticeably quieter than the 1,088 RPM single-stage under load
- You're planning for maximum pump longevity — the slower RPM and superior bearing design of the two-stage unit give it a longer expected service life
The single-stage C518HA8 is the right call if: 125 PSI is adequate for your tools and you want to save on purchase cost (typically around $250 less). For most general automotive shop air tool use, 125 PSI is sufficient.
Factory Options
- Air Operated Auto Drain (#ADVSM): Automatic condensate drain
- Electronic Auto Drain (#SDV03M): Timer-controlled drain valve
- Silencer 1" (#SA100M): Intake noise silencer
- Belt Guard Aftercooler (#BGAC1M): 35 CFM aftercooler
- Vibration Pads (#VP1004): 4x4x1" rubber isolation pads (set of 4)
- Right From the Start Kit (#RFS001): Oil, pads, ball valve, flex hose, filter element
What's in the Box
- Assembled compressor (two-stage pump, motor, 80-gallon horizontal 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 (required before first start), vibration pads, flex hose
Why Buy From Air Compressor Factory Direct?
We specialize in commercial and industrial air compressors and carry the full Castair lineup. Free shipping on qualifying orders. Free tech support at 866-217-0063. Full manufacturer warranty. We can help you decide between single-stage and two-stage options for your shop's specific pressure and noise requirements.
Call 866-217-0063 for quick answers and help!
