The Castair D7324HC1-S is a 15HP (2×7.5HP) three-phase duplex air compressor on a 240-gallon horizontal ASME tank with twin C1 cast iron pumps running at 895 RPM. This configuration is built for three-phase shops that need large air storage volume combined with duplex redundancy — shops where the compressor runs continuously through long workdays and where cycling frequency matters as much as raw output.
At 1,560 lbs. on a 240-gallon tank, this is a serious commercial installation. The three-phase motors deliver 49.6 CFM at 175 PSI while drawing lower amperage than single-phase equivalents of the same horsepower. The 240-gallon tank means your pumps cycle significantly less often under the same air demand compared to the 120-gallon version — which translates directly into lower pump temperatures, lower motor start frequency, and longer component life across the board.
Who Needs the D7324HC1-S
Three-phase commercial shops with sustained air demand and the floor space for a 240-gallon horizontal machine. Auto repair shops, fleet maintenance facilities, tire centers, and light manufacturing operations where multiple air tools run simultaneously through the workday. The duplex configuration provides backup redundancy — when one pump needs service, the other keeps the shop running.
The 240-gallon tank is particularly valuable for operations that run air-intensive equipment in bursts — sandblasters, plasma cutters, automated spray systems, or large impact tools. The larger reservoir absorbs those peak demand spikes without immediately cycling the pumps back on, which reduces heat cycles in the pump and motor assemblies over time.
Castair C1 Pump Features
- All cast iron construction: Cylinders, crankcase, and valve plates are cast iron throughout. Cast iron handles sustained duty better than aluminum — it runs quieter, maintains tighter tolerances through thermal cycles, and lasts longer in continuous-duty commercial applications.
- 895 RPM operating speed: The C1 pump runs at 895 RPM — roughly half the speed of most imported pump assemblies. Slower RPM means lower operating temperature and longer service life for bearings, rings, and valves.
- Tapered roller bearings: Both ends of each crankshaft use tapered roller bearings — the correct bearing type for the combined radial and axial loads in a reciprocating compressor crankshaft.
- Precision steel connecting rods: Automotive-type rod insert bearings at the crankshaft journal and at the wrist pin. This is how long-life industrial reciprocating machines are built — not with pressed pins and loose-tolerance bores.
- Disc and spring valves: More durable and more efficient than reed valves under sustained duty. When valves wear, you service the valves — not the pump head.
- 4-ring pistons: Four compression rings per piston for better sealing efficiency and lower oil carry-over into the air supply. This matters for spray work and precision pneumatic tooling.
- Centrifugal unloader: Loadless start on every cycle. The pump reaches speed before compression load engages — less motor stress, longer motor life, especially important in high-cycle applications.
Tank, Motor, and Control Features
- 240-gallon horizontal ASME tank: Powder-coated steel with channel base for floor stability. ASME certified — designed, constructed, and tested to meet pressure vessel safety standards.
- ASME safety valves: Factory-original certified pressure relief hardware.
- Fully enclosed metal belt guard: Safety compliance and drive system protection.
- Copper discharge and unloader tube or stainless-steel braided flex line: Copper or stainless in all discharge path connections — no plastic where heat and pressure are present.
- Heavy-duty 1725 RPM three-phase industrial motors: Full 15% service factor or higher. Three-phase motors start cleanly without capacitors or centrifugal switches, draw lower amperage per HP than single-phase, and run cooler under sustained loads.
- Magnetic starter mounted and wired (-S models): Factory-installed and pre-wired magnetic motor starters. Connect your three-phase electrical service to the panel — the internal wiring is done.
240-Gallon Tank: The Operational Advantage
Both the 120-gallon D7312HC1-S and the 240-gallon D7324HC1-S deliver 49.6 CFM at 175 PSI from the same C1 pumps. The difference is entirely about cycle management.
A 240-gallon tank takes twice as long to drop from cut-out pressure to cut-in pressure under the same air draw rate as a 120-gallon tank. That means half as many pump starts per hour, half as many heat cycles per hour, and half as many motor inrush events per hour. Over a 10-hour workday, the difference between 30 and 15 pump starts is significant for long-term pump and motor health. If your shop runs the compressor hard all day, the 240-gallon tank pays back its extra cost in extended pump life.
Factory-Mounted Options Available
- Low Oil Control (#6304x2M): Automatic shutdown before oil starvation can cause internal pump damage. Essential for high-duty or unattended operation.
- Hour Meter (#HRM75x2M for 230V, #HRM460x2M for 460V): Track actual operating hours for both pump units — the foundation of interval-based maintenance scheduling.
- Alternator (#ALT230M or #ALT460M): Automatic cycle-by-cycle alternation between pump units to equalize long-term run hours and wear.
- Electronic Auto Drain (#SDV03M): Timed condensate purge. Tanks not drained regularly accumulate moisture and corrode internally. This automates that maintenance requirement.
- Dual Control (#DC1x2M for C1 duplex): Enables continuous unloaded operation mode during sustained high-demand periods. Reduces motor start frequency, which directly reduces electrical cost and motor wear. Note: Dual control is not recommended on units with alternators installed.
- Intake Noise Silencers (#SA100x2M for C1 duplex): Inlet silencers on each pump head reduce intake noise without restricting airflow.
- Belt Tensioner (#215Dx2M for 7.5-10HP): Spring-loaded belt tensioner for consistent drive geometry as belts stretch during break-in and normal use.
- Right From the Start Kit (#RFS001D for 10HP): Maintenance kit for first-service interval, consolidated in one package.
- Vibration Pads (#VP1004): Isolation pads to reduce floor vibration transmission from the unit.
- Belt Guard Aftercooler (#BGAC1x2M, 70 CFM for 10-20HP units): Reduces compressed air temperature and moisture content before the air enters the tank — worthwhile for shops with moisture-sensitive applications.
- All Options Bundle (#AOC1D for C1): Order all asterisk options together for 10% off the options total.
Available Configurations — 7.5HP Three-Phase Duplex
- D7312HC1-S: 2×7.5HP, three-phase, C1 pump (895 RPM), 120-gal, 49.6 CFM@175 PSI, 1,210 lbs. — same pumps, smaller tank, lower weight.
- D7312HC2-S: 2×7.5HP, three-phase, C2 pump (585 RPM), 120-gal, 56.2 CFM@175 PSI, 1,400 lbs. — higher CFM, heavier pump, 120-gal tank.
- D7324HC1-S (this unit): 2×7.5HP, three-phase, C1 pump (895 RPM), 240-gal, 49.6 CFM@175 PSI, 1,560 lbs. — same pump output, larger storage, longer pump life in high-use applications.
- D7324HC2-S: 2×7.5HP, three-phase, C2 pump (585 RPM), 240-gal, 56.2 CFM@175 PSI, 1,750 lbs. — maximum output and storage in three-phase 7.5HP duplex.
When Does a Shop Need This vs. Stepping Up or Down
- Step down (D7312HC1-S, 120-gallon): If floor space is limited or your demand does not justify the larger storage volume, the 120-gallon C1 version delivers the same 49.6 CFM with more frequent cycling. Saves 350 lbs. and floor space.
- This unit (D7324HC1-S): Three-phase power, sustained daily demand, floor space for a 240-gallon unit, need for duplex redundancy. The right configuration for any three-phase shop that wants low cycle frequency and long pump life from a C1 pump setup.
- Step up (C2 pump): If you need 56 CFM instead of 49.6 at 175 PSI, the D7324HC2-S uses the same 240-gallon tank with the C2 pump upgrade. Same frame, more CFM per cycle, heavier pump.
Technical Specifications
- Model: D7324HC1-S
- Configuration: Duplex (2 pumps, 2 motors)
- Motor: 2×7.5HP, 15HP total
- Phase: Three-phase
- Pump Series: C1 (cast iron)
- Pump RPM: 895
- CFM @ 0 PSI: 64.8
- CFM @ 175 PSI: 49.6
- Tank: 240-gallon horizontal ASME
- Dimensions (L×W×H): 85 × 30 × 64 inches
- Weight: 1,560 lbs.
- Magnetic Starter: Included, factory-mounted and wired
- Max Pressure: 175 PSI
Why Buy From Air Compressor Factory Direct?
We have been selling and supporting professional-grade air compressors since 2016. We carry the full Castair duplex lineup in every configuration — both pump series, all tank sizes, single-phase and three-phase. Free shipping on all orders. Free tech support at 866-217-0063 — call before you order if you want help comparing pump series options, calculating whether your three-phase amperage service supports this unit, or working out the right tank size for your shop's demand profile. Full manufacturer warranty on all units. Honest guidance — we will tell you if a smaller or different configuration is the better fit for your situation.
Call 866-217-0063 for quick answers and help!
