Castair I15312VC3-S: 15HP 3-Phase Industrial Air Compressor — 120 Gallon Vertical (Base Unit)
The Castair I15312VC3-S listed under SKU I15312VC3 is the 15-horsepower, 3-phase, 120-gallon vertical industrial compressor built on Castair's heavy-duty C3 cast iron pump. This is the base configuration — no aftercooler included — giving you the full performance of the C3 pump platform at a lower entry price. If your shop has adequate air drying equipment downstream, or your application does not require aftercooler treatment, this is the configuration to buy.
The C3 pump runs at 795 RPM — well below the 1,100+ RPM you see on cheaper industrial units. Slower RPM means lower operating temperature, less wear per hour of runtime, and longer intervals between valve and ring service. For a shop that runs their compressor 8 or more hours a day, that difference compounds into years of additional pump life.
At 61.7 CFM free air delivery and 50.2 CFM at 175 PSI, this unit can supply 3-5 technicians running standard shop air tools simultaneously. The 120-gallon vertical tank provides adequate storage to buffer peak demand without the compressor cycling constantly.
Pump Design and Construction
C3 Cast Iron Pump — Core Specs
- Pump designation: C3 — Two-stage, W3 cylinder configuration
- Operating RPM: 795 — slow-speed operation for extended pump life
- Construction: 100% cast iron — cylinders, heads, valve plates, crankcase
- Bearings: Tapered roller bearings at both ends of the crankshaft for superior support and minimal friction
- Connecting rods: Precision steel with automotive-type rod insert bearings at crankshaft and wrist pin
- Valves: Disc and spring design — easy to service, replaceable without specialized tooling
- Pistons: 4-ring configuration for high efficiency and low oil carry-over
- Unloader: Centrifugal unloader for loadless start-up — pump starts without load every time, protecting motor and belts
- Oil capacity: 1 gallon
Tank and Frame
- Tank capacity: 120 gallons, vertical orientation
- Tank finish: Powder-coated ASME-rated steel
- Leg configuration: 4 legs (vertical models)
- Safety valve: ASME-rated, factory installed
- Belt guard: Totally enclosed metal construction
- Discharge lines: Copper tubing or stainless braided flex line
Motor
- Horsepower: 15HP
- Phase: 3-phase
- Base motor speed: 1725 RPM industrial
- Service factor: 15% or higher
- Max operating pressure: 175 PSI
Performance Specifications
- Motor output: 15 HP
- Electrical requirement: 3-phase
- Tank capacity: 120 gallons, vertical
- Pump RPM: 795
- Free air delivery (0 PSI): 61.7 CFM
- Delivery at 175 PSI: 50.2 CFM
- Max pressure: 175 PSI
- Dimensions (LxWxH): 44 x 30 x 82 inches
- Weight: 1,185 lbs
- Aftercooler: Not included (available as BGAC2M option)
What's in the Box
- Castair I15312VC3-S compressor — fully assembled (base unit)
- ASME safety valve (factory installed)
- Pressure switch with unloader
- Totally enclosed metal belt guard
- Copper discharge and unloader tubing (or stainless braided flex line)
- Owner's documentation
Note: Aftercooler and magnetic motor starter are not included in the base configuration. Both are available as factory-mounted options. Electrical installation requires a licensed electrician familiar with 3-phase motor wiring.
Available Configurations — 15HP Industrial Series
- I15312VC2-S: 15HP, 3-phase, 120gal Vertical, C2 pump, 898 RPM, 45.3 CFM @ 175 PSI, 980 lbs — lighter unit with slightly lower CFM output
- I15312HC2-S: 15HP, 3-phase, 120gal Horizontal, C2 pump, 898 RPM, 45.3 CFM @ 175 PSI, 980 lbs
- I15312VC3-S (this unit): 15HP, 3-phase, 120gal Vertical, C3 pump, 795 RPM, 50.2 CFM @ 175 PSI, 1,185 lbs
- I15312HC3-S: 15HP, 3-phase, 120gal Horizontal, C3 pump, 795 RPM, 50.2 CFM @ 175 PSI, 1,185 lbs
The C3 pump delivers 50.2 CFM at 175 PSI versus 45.3 CFM from the C2 — about 11% more usable air from the same 15HP motor. The C3 accomplishes this by using a larger W3 cylinder configuration and running at slower RPM. If your shop is regularly running at or near the C2's capacity limit, the C3 is worth the additional weight and cost.
When Does a Shop Need This vs. Stepping Up or Down?
I15312VC3-S is the right choice when:
- You need 3 to 5 simultaneous technician workstations running standard pneumatic tools
- 3-phase electrical service is available at your facility
- You want maximum CFM from a 15HP / 120-gallon vertical configuration
- Your application does not require aftercooler-treated air (or you have downstream drying equipment)
Consider the aftercooler (-S with BGAC2M) if:
- You are running spray guns, sandblasting, or other moisture-sensitive processes — the BGAC2M aftercooler is a factory-mounted option that pays for itself quickly in reduced moisture-related problems
Step down if:
- You are running 1-2 technicians — the 10HP series handles smaller shops at significantly lower electrical cost
Step up to 20-30HP if:
- You are running a large multi-bay operation or spray booth requiring consistent 70+ CFM — the I20324HC4Z-S and I25324HC4Z-S are sized for those applications
Why Buy From Air Compressor Factory Direct?
Since 2016, we have specialized in selling industrial air compressors and shop equipment. When you call us, you talk to someone who understands Castair's pump designations, motor wiring requirements, and how to size a compressor to your actual shop workflow — not just your floor space.
- Free shipping to commercial addresses in the lower 48 states
- Free tech support at 866-217-0063 — before and after your purchase
- Full Castair manufacturer warranty
- Honest configuration guidance — we will tell you if you need a different model
- Authorized dealer with direct Castair factory support access
Call 866-217-0063 for quick answers and help!
