The Castair I15312HC3-S is a 15-horsepower, 3-phase industrial air compressor on a 120-gallon horizontal tank with the C3 pump — the large-frame, slow-speed configuration running at 795 RPM. This is the highest-output 15HP option in the Castair industrial line, delivering 50.2 CFM at 175 PSI. Compared to the 15HP C2 configuration (898 RPM, 45.3 CFM at 175 PSI), the C3 pump runs slower, outputs more air, and weighs substantially more — 1,185 lbs versus 980 lbs. The horizontal tank sits at 69x24x62 inches. If your shop needs the maximum CFM available in a 15HP 3-phase horizontal configuration, this is it.
Who Needs the C3 Configuration
High-production shops where the compressor runs continuously under heavy load, and where both maximum output and minimum wear rate are priorities. The C3 pump delivers 50.2 CFM at 175 PSI — enough to sustain a high-demand sandblasting operation, run multiple spray guns simultaneously, or supply a production line with heavy pneumatic tooling. The slower RPM (795 vs 898) means proportionally less wear per hour, which matters when the compressor runs 8-10 hours a day in a production environment.
If the extra 205 lbs and the higher cost of the C3 are not justified by your actual CFM demand, the I15312HC2-S at 45.3 CFM and 980 lbs is the better value for most shops.
C3 Pump Features
- All cast iron construction — cylinders, heads, crankcase. Larger frame than the C2 — this is a bigger pump physically.
- 795 RPM pump speed — significantly slower than the C2 (898 RPM) and well below the 1000+ RPM of budget compressors. Lower RPM means cooler operation and less mechanical wear per hour.
- Tapered roller bearings at both ends of the crankshaft.
- Steel connecting rods with automotive-type insert bearings — at crankshaft and wrist pin. Replaceable for long-term serviceability.
- Disc and spring valves.
- 4-ring pistons — better sealing, less oil carry-over.
- Centrifugal unloader — loadless motor starts every time.
Tank, Motor, and Controls
- 120-gallon horizontal ASME tank — powder coated, channel base, 69x24x62 inches. Note: the C3 tank is taller than the C2 (62 in. vs 50 in.) due to the larger pump assembly.
- ASME safety valve.
- 1725 RPM industrial 15HP motor — 15% service factor minimum.
- Totally enclosed metal belt guard.
- Copper discharge tube or stainless-steel braided flex line.
- Magnetic motor starter — included, factory mounted and wired.
15HP Industrial Line Comparison
- I15312VC2-S — 120-gallon vertical, C2 pump (898 RPM), 45.3 CFM @175 PSI, 44x30x75 in., 980 lbs, with starter.
- I15312HC2-S — 120-gallon horizontal, C2 pump (898 RPM), 45.3 CFM @175 PSI, 69x24x50 in., 980 lbs, with starter.
- I15312VC3-S — 120-gallon vertical, C3 pump (795 RPM), 50.2 CFM @175 PSI, 44x30x82 in., 1185 lbs, with starter.
- I15312HC3-S (this unit) — 120-gallon horizontal, C3 pump (795 RPM), 50.2 CFM @175 PSI, 69x24x62 in., 1185 lbs, with starter.
Factory Options
- Low oil shutdown — #6304M.
- Hour meter — #HRM460M (460V) or #HRM75M (230V).
- Electronic auto drain — #SDV03M.
- Dual control — #DC3 (standard on C3). Load/unload cycling for energy savings.
- Intake noise silencer — #SA100x2M.
- Belt tensioner — #254DM (15HP).
- Beltguard aftercooler — #BGAC2M (50 CFM, 15HP).
- All Options C3 package — #AOC3 (10% off all asterisk options).
- Vibration pads — #VP1004, set of 4.
- Right from the Start Kit — #RFS002 (C3).
Technical Specifications
- Model Number: I15312HC3-S
- Horsepower: 15 HP
- Phase: 3-phase
- Tank Capacity: 120 gallons, horizontal
- Pump RPM: 795
- CFM @ 0 PSI: 61.7
- CFM @ 175 PSI: 50.2
- Max Pressure: 175 PSI
- Dimensions (LxWxH): 69 x 24 x 62 inches
- Weight: 1,185 lbs
- Motor Speed: 1725 RPM
- Motor Service Factor: 15% minimum
- Tank Certification: ASME
- Magnetic Starter: Included (factory mounted)
- Pump Configuration: C3
Why Buy From Air Compressor Factory Direct?
We have specialized in industrial air compressors since 2016. At this level of equipment, the difference between the C2 and C3 configurations is a meaningful decision — call us and we will help you determine whether the additional 5 CFM and lower RPM of the C3 justify the additional cost for your specific duty cycle. Free shipping, free pre-sale technical support, full manufacturer warranty.
Call 866-217-0063 for quick answers and help!
