Cast Air Heavy Duty Shop Tandem Air Compressor — T20312HC3-S
The T20312HC3-S runs two 20 HP motors on the HC3 cast iron pump at 570 RPM — the slowest, largest pump configuration Cast Air makes for this horsepower range. Combined output is 180 CFM at 0 PSI and 140 CFM at 175 PSI, identical to the HC2 tandem, but achieved at dramatically lower pump speed. The 120-gallon horizontal ASME tank keeps the footprint manageable. At $10,285, you pay a premium over the HC2 configuration ($7,974) for slower RPM, lower operating temperature, reduced noise, and extended service life between major pump maintenance intervals. This is the compressor for shops where the machine runs all day, every day, and long-term cost of ownership matters more than the initial purchase price.
HC2 vs. HC3 — Is the Difference Worth It?
- HC2 (758 RPM, $7,974): Delivers the same 140 CFM at 175 PSI as the HC3 at a lower purchase price. The right choice for shops with heavy but not continuous demand where pump service intervals of 4,000–6,000 hours are acceptable.
- HC3 (570 RPM, $10,285): The HC3 pump is physically larger and runs at 570 RPM — 25% slower than the HC2. Lower RPM means lower operating temperature, less vibration, and longer intervals between valve and ring replacement. For shops running the compressor 8–10+ hours per day, the HC3's longer service life and lower noise level pay back the $2,311 premium over time.
- Bottom line: If your compressor runs hard all day in a production environment, the HC3 is the correct specification. If your demand is heavy but intermittent, the HC2 is the more economical choice.
Cast Iron Pump Features
- All cast iron construction: Cylinders, heads, and crankcase on both pumps. The HC3 is the largest cast iron pump in the Cast Air industrial piston lineup.
- 570 RPM (HC3 configuration): The slowest operating speed in the Shop Tandem series. At 570 RPM, the pump is running at a fraction of the speed of import equipment — significantly quieter and generating far less heat per cubic foot of air compressed.
- Tapered roller bearings: Both ends of each crankshaft. Required for sustained high-load operation at any RPM.
- Precision steel connecting rods: Automotive-type rod insert bearings at the crank, needle bearings at the wrist pin.
- Disc and spring valves: Simple to service in the field. At 570 RPM, valve wear is substantially reduced compared to faster pumps running the same duty cycle.
- 4-ring pistons: Higher efficiency, less oil carry-over.
- Centrifugal unloader: Loadless start every cycle. At 40 HP total, protecting the electrical service from inrush current is not optional — the centrifugal unloader handles it automatically.
Tank and Controls
- 120-gallon horizontal ASME tank: Powder-coated, channel base. At 140 CFM of pump output, the 120-gallon tank charges quickly. Add the HC3's slower recovery time relative to its lower RPM, and the 240-gallon T20324HC3-S is the better choice if your demand has significant spikes.
- Two magnetic motor starters — mounted and wired: Factory-installed on both pump sides. Ready to connect to 3-phase service.
- ASME safety valves: Factory-set on both sides.
- Metal belt guards: Fully enclosed on both assemblies.
- Copper discharge and unloader tubes: Copper throughout the hot side.
- 1,725 RPM industrial motors: 15% service factor or higher.
Available Factory-Mounted Options
- Low Oil Control (#6304x2M): Essential for any production environment where the compressor runs unattended.
- Hour Meter 230V (#HRM75x2M) or 460V (#HRM460x2M): Track runtime on each pump independently.
- Alternator Relay (#ALT230M or #ALT460M): Equalizes wear between both pump sides automatically.
- Electronic Auto Drain (#SDV03M): Timed solenoid condensate drain.
- Dual Control (#DC2x2M): Start/stop and throttle control modes. Standard on HC3 configurations.
- Intake Noise Silencers (#SA100x4M): The HC3 is already quieter at 570 RPM — silencers reduce intake noise further if the compressor room is near the work area.
- Aftercooler (#BGAC1x2M, 70 CFM rated): Belt-guard-mounted aftercooler on both pump sides.
- All Options Package (#AOC3D): All asterisk options at 10% off. Note: Dual control is standard on HC3 units; cannot combine intake silencers and dual control on HC3.
What Is in the Box
- Two cast iron two-stage HC3 pump and motor assemblies (20 HP each) on a single rigid frame
- 120-gallon horizontal powder-coated ASME tank with channel base
- Two magnetic motor starters, mounted and wired at the factory
- Two ASME safety valves
- Two metal belt guards (fully enclosed)
- Copper discharge and unloader tubes on both sides
- Pressure switch for each pump
Optional accessories are factory-installed at time of order and are not included unless specified at purchase.
Available Configurations — 20 HP Shop Tandem Lineup
- T20312HC2-S: 2×20 HP, 758 RPM, 180 CFM / 140 CFM @ 175 PSI, 120-gal — $7,974
- T20312HC3-S: 2×20 HP, 570 RPM, 180 CFM / 140 CFM @ 175 PSI, 120-gal — $10,285 (this unit)
- T20324HC2-S: 2×20 HP, 758 RPM, 180 CFM / 140 CFM @ 175 PSI, 240-gal — $9,460
- T20324HC3-S: 2×20 HP, 570 RPM, 180 CFM / 140 CFM @ 175 PSI, 240-gal — $11,610
When Does a Shop Need This vs. Stepping Up or Down?
- Step down to HC2: If your compressor runs 6 hours per day or less with recovery time, the T20312HC2-S at $7,974 delivers identical CFM output for $2,311 less. Spend that savings on a good aftercooler and auto drain package.
- This unit is right when: You run an automotive production line, a high-volume collision repair shop, or any operation where the compressor cycles continuously 8–12 hours per day. The HC3 pump's 570 RPM operating speed pays back its premium in lower maintenance costs and longer service life at those duty levels.
- Consider 240-gallon tank: For production environments with burst demand, the T20324HC3-S adds 120 gallons of receiver storage for $1,325 more — worth it if pressure stability during peak demand is a priority.
Technical Specifications — T20312HC3-S
- Model Number: T20312HC3-S
- Horsepower: 2 × 20 HP (40 HP total)
- Phase: 3-phase
- Pump RPM: 570 (HC3 configuration)
- CFM @ 0 PSI: 180 (combined, both pumps)
- CFM @ 175 PSI: 140 (combined, both pumps)
- Tank Capacity: 120 gallons, horizontal
- Tank Type: ASME-certified, powder-coated, channel base
- Motor Speed: 1,725 RPM, 15% service factor
- Pump Type: Two-stage, all cast iron, centrifugal unloader
- Controls: Two magnetic motor starters, mounted and wired; Dual Control standard
- Discharge Tubing: Copper
- Belt Guard: Metal, fully enclosed
- Price: $10,285.35
Note: Exact LxWxH dimensions and shipping weight for this configuration are not individually published by Castair. Contact us for freight details before ordering.
Why Buy From Air Compressor Factory Direct?
We have specialized in industrial air compressor sales since 2016. The HC2 vs. HC3 decision is one of the most common questions we field — and the answer genuinely depends on your specific duty cycle, not just the price. We will tell you which configuration actually fits your operation.
- Free shipping to a commercial address with a loading dock or forklift
- Free tech support at 866-217-0063 — we will help you assess whether HC2 or HC3 is right for your shop's actual duty cycle
- Full Cast Air manufacturer warranty — handled directly through us
- Honest upgrade guidance: We carry the full Cast Air lineup. If a different configuration fits better, we will tell you.
Call 866-217-0063 for quick answers and help!
