Cast Air Heavy Duty Shop Tandem Air Compressor — T20312HC2-S
The T20312HC2-S pairs two 20 HP motors with HC2 cast iron pumps at 758 RPM on a 120-gallon horizontal ASME tank. Combined output is 180 CFM at 0 PSI and 140 CFM at 175 PSI. At $7,974, this is the entry point in the 20 HP tandem series and the most cost-effective way to get 140 CFM at working pressure in a piston compressor. The 120-gallon tank keeps the footprint compact relative to the output; the dual 20 HP pumps mean you are running with genuine production-level air capacity. This machine is built for body shops, fleet maintenance operations, automotive assembly lines, and any shop where air demand consistently outpaces what a 15 HP machine can supply.
What 140 CFM at 175 PSI Actually Means
- A typical 1/2-inch impact wrench needs 4–5 CFM at 90 PSI. You could run 28+ impacts simultaneously at 90 PSI with this compressor's output.
- A DA sander runs 12–14 CFM. You can run 10 DA sanders at once at full speed.
- A spray gun runs 10–15 CFM at 40–50 PSI. Multiple painters working simultaneously is no problem.
- The point: at 140 CFM, you are not rationing air. Every tool in every bay can run at rated performance simultaneously.
Cast Iron Pump Features
- All cast iron construction: Cylinders, heads, and crankcase on both pumps. Cast iron is the only material that makes sense for a compressor running at this load level for years.
- 758 RPM (HC2 configuration): The HC2 pump on a 20 HP motor runs at 758 RPM — slow enough that the compressor room stays tolerable to work near, and slow enough that heat buildup is not a constant maintenance issue.
- Tapered roller bearings: Both ends of each crankshaft. Required for sustained heavy-load operation.
- Precision steel connecting rods: Automotive-type rod insert bearings at the crank, needle bearings at the wrist pin.
- Disc and spring valves: The highest-wear item in any piston compressor. Cast Air's disc/spring design is simpler to service than reed valves and holds up better under sustained high-output operation.
- 4-ring pistons: Higher volumetric efficiency, less oil carry-over into the discharge air.
- Centrifugal unloader: Loadless start on every cycle. At 20 HP per motor, a hard start is 40 HP of inrush current on your electrical service — the centrifugal unloader eliminates that.
Tank and Controls
- 120-gallon horizontal ASME tank: Powder-coated, channel base. At 140 CFM of pump output, the 120-gallon receiver charges and recovers quickly. If your demand comes in intense bursts rather than a sustained draw, consider the 240-gallon T20324HC2-S for more buffer storage.
- Two magnetic motor starters — mounted and wired: Both motor starters factory-installed. Connect to 3-phase service and operate.
- ASME safety valves: Factory-set on both pump sides.
- Metal belt guards: Fully enclosed on both pump assemblies.
- Copper discharge and unloader tubes: No rubber hose on the hot side.
- 1,725 RPM industrial motors: 15% service factor or higher. At 20 HP per side, these are substantial motors built for continuous industrial service.
Available Factory-Mounted Options
- Low Oil Control (#6304x2M): Automatic oil-level shutdown on both pumps — essential at this horsepower level.
- Hour Meter 230V (#HRM75x2M) or 460V (#HRM460x2M): Track runtime independently on each pump for scheduled maintenance.
- Alternator Relay (#ALT230M or #ALT460M): Alternates lead pump automatically to equalize wear.
- Electronic Auto Drain (#SDV03M): Timed solenoid condensate drain. The larger tank produces more condensate — the auto drain keeps it managed.
- Dual Control (#DC2x2M): Start/stop and throttle control modes.
- Intake Noise Silencers (#SA100x4M): Reduces intake noise on both pumps.
- Belt Tensioner (#215Dx2M for 7.5–10 HP; contact us for 20 HP spec): Self-tensioning motor base system.
- Aftercooler (#BGAC1x2M, 70 CFM rated per unit): Belt-guard-mounted aftercooler on both pump sides.
- All Options Package (#AOC2D): All asterisk options at 10% off combined price.
What Is in the Box
- Two cast iron two-stage HC2 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 (this unit)
- T20312HC3-S: 2×20 HP, 570 RPM, 180 CFM / 140 CFM @ 175 PSI, 120-gal — $10,285 (slowest pump, quietest, longest life)
- T20324HC2-S: 2×20 HP, 758 RPM, 180 CFM / 140 CFM @ 175 PSI, 240-gal — $9,460 (more buffer storage)
- T20324HC3-S: 2×20 HP, 570 RPM, 180 CFM / 140 CFM @ 175 PSI, 240-gal — $11,610 (maximum configuration)
The HC2 and HC3 configurations produce the same combined CFM — the HC3 pump is physically larger and runs at 570 RPM vs. 758 RPM on the HC2. If your shop environment demands the quietest possible operation and maximum longevity between pump services, the HC3 is worth the additional cost. If noise is less critical, the HC2 delivers equivalent air output for less money.
When Does a Shop Need This vs. Stepping Up or Down?
- Step down to 15 HP tandem: If your peak demand is under 100 CFM and you have some recovery time, the 15 HP tandem lineup handles it for $1,000–3,000 less. The 20 HP tandem is for shops that genuinely need 140 CFM sustained, not shops that occasionally spike near it.
- This unit is right when: You operate a large body shop, collision repair center, or automotive production facility where air demand is consistently high. 140 CFM at 175 PSI runs a serious shop with headroom to spare.
- Step up to 25–30 HP tandem: If 140 CFM is not enough — multiple spray booths, heavy air tools, large-volume tire inflation — the T25312HC2-S or T30312HC3-S deliver 180–210 CFM at 175 PSI on the same general platform.
- Consider 240-gallon tank: If your demand comes in intense bursts rather than a steady draw, the T20324HC2-S adds 120 gallons of receiver storage for $1,486 more.
Technical Specifications — T20312HC2-S
- Model Number: T20312HC2-S
- Horsepower: 2 × 20 HP (40 HP total)
- Phase: 3-phase
- Pump RPM: 758 (HC2 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
- Discharge Tubing: Copper
- Belt Guard: Metal, fully enclosed
- Price: $7,973.60
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. At the 20 HP tandem level, getting the right configuration matters — the difference between HC2 and HC3, and between 120 and 240-gallon tanks, is significant in both price and application fit. When you buy through us:
- Free shipping to a commercial address with a loading dock or forklift
- Free tech support at 866-217-0063 — we will help you confirm whether HC2 or HC3 is the right pump for your application
- Full Cast Air manufacturer warranty — we handle warranty claims directly with Cast Air
- Honest upgrade guidance: If the 15 HP tandem handles your load, we will tell you. If you need 25 HP, we will say that too.
Call 866-217-0063 for quick answers and help!
