The Castair D10112HC3-S is a 20 total horsepower duplex two-stage air compressor on a 120-gallon horizontal ASME tank, running on single-phase electricity. It uses the HC3 pump configuration — running at 570 RPM, slower than the HC2 — which means quieter operation, lower running temperatures, and longer pump life in exchange for a larger physical footprint (94" x 28" x 57" vs. 85" for the HC2 frame). It delivers 70 CFM at 175 PSI combined from two 10 HP cast iron pumps, with a magnetic starter mounted and wired at the factory.
HC3 vs. HC2 — The Key Difference
The HC2 and HC3 designations refer to the pump size and speed. Both deliver the same rated CFM (90 at 0 PSI, 70 at 175 PSI combined for the 2x10HP configuration), but the HC3 achieves that output at a lower RPM using a larger displacement pump:
- HC2 pump: 758 RPM, 85" frame length, 1,470 lbs
- HC3 pump: 570 RPM, 94" frame length, 1,800 lbs
Slower RPM means the pump runs cooler, valve wear is reduced, and the unit operates more quietly. If your shop has noise-sensitive areas or you plan to run this machine hard for long cycles, the HC3 is worth the extra weight and frame length.
Pump and Motor Specifications
- Configuration: Duplex (two pumps, two motors)
- Total HP: 20 HP (2 x 10 HP)
- Phase: Single-phase
- Pump RPM: 570 (HC3 pump)
- CFM at 0 PSI: 90 CFM combined
- CFM at 175 PSI: 70 CFM combined
- Max Pressure: 175 PSI
- Stage: Two-stage
Tank and Physical Specs
- Tank Capacity: 120 gallons, horizontal ASME
- Dimensions (LxWxH): 94" x 28" x 57"
- Weight: 1,800 lbs
- Tank Finish: Powder coated
- Safety Valve: ASME rated, installed
- Magnetic Starter: Mounted and wired (factory installed)
Cast Iron Pump Features
- All cast iron construction for long service life and quiet operation
- Slow RPM design (570 RPM) — lower than HC2 for even quieter, cooler operation
- Tapered roller bearings at both ends of crankshaft
- Precision steel connecting rods with automotive-type rod insert bearings
- Disc and spring valves for easy service and reliability
- 4-ring pistons for higher efficiency and less oil carry-over
- Centrifugal unloader for loadless start-up
Factory-Mounted Options Available
- Low Oil Control — #6304x2M
- Hour Meter 230V — #HRM75x2M | 460V — #HRM460x2M
- Alternator — #ALT230M | #ALT460M
- Electronic Auto Drain — #SDV03M
- Dual Control (standard on C3) — included on this unit
- Intake Noise Silencers (C2/C3) — #SA100x4M (note: cannot combine with dual control on C3)
- Belt Tensioner (7.5-10HP) — #215Dx2M
- Right From the Start Kit — #RFS001D (10HP)
- Vibration Pads — #VP1004
- Beltguard Aftercooler — #BGAC1x2M
- All Options C3 Package — #AOC3D
Duplex Configuration Comparison — 2x10HP Single-Phase
- D10112HC2-S — 758 RPM HC2 pump, 120gal, 85x28x57, 1,470 lbs — smaller footprint, lighter
- D10112HC3-S — 570 RPM HC3 pump, 120gal, 94x28x57, 1,800 lbs — slower/quieter pump (this unit)
- D10124HC2-S — HC2 pump, 240-gallon tank, 1,820 lbs — more storage
- D10124HC3-S — HC3 pump, 240-gallon tank, 2,150 lbs — max storage + slowest RPM
When Does a Shop Need This vs. Stepping Up or Down
Choose the D10112HC3-S over the D10112HC2-S when: Noise level matters (body shop, customer-facing areas), or the compressor will run extended duty cycles where keeping the pump cool is a priority. The 570 RPM HC3 pump is the better long-term choice for high-utilization shops even though it weighs 330 lbs more and costs more upfront.
Step down to D10112HC2-S if floor space or ceiling height is tight (the HC3 frame is 9" longer), or if budget is the primary constraint — same rated CFM output, just at a higher RPM.
Step up to D10124HC3-S if your shop runs long continuous cycles that exhaust 120 gallons before the pumps catch up — adding 120 gallons of storage smooths out pressure swings during peak demand.
Consider three-phase (D10312HC3-S or D10324HC3-S) if three-phase service is available. Three-phase motors at 10 HP run more efficiently and last longer than single-phase units of equivalent rating.
Technical Specifications Summary
- Model: D10112HC3-S
- Manufacturer: Castair (Cast Air, Inc.) — Spicer, Minnesota
- Configuration: Duplex, two-stage, electric
- Total HP: 20 HP (2 x 10 HP)
- Phase: Single-phase
- Pump RPM: 570 (HC3)
- CFM @ 0 PSI: 90
- CFM @ 175 PSI: 70
- Tank: 120 gallon, horizontal, ASME, powder coated
- Dimensions (LxWxH): 94" x 28" x 57"
- Weight: 1,800 lbs
- Magnetic Starter: Included, factory mounted and wired
- Safety Valve: ASME rated, installed
Why Buy From Air Compressor Factory Direct?
We have been selling industrial air compressors since 2016. The D10112HC3-S is a $12,000+ capital investment and the pump/tank/motor configuration decision matters. We can walk you through the HC2 vs. HC3 comparison, help you choose the right tank size, and advise on electrical service requirements. Free shipping, free technical support at 866-217-0063, and the full Castair manufacturer warranty on every unit we sell.
Call 866-217-0063 for quick answers and help!
Frequently Asked Questions
What is the advantage of a duplex compressor like the D10112HC3-S over a single-pump unit?
A duplex gives you redundancy and load-sharing in one cabinet. On the D10112HC3-S, two 10 HP cast iron pumps alternate duty cycles, so each pump runs roughly half the hours of a single 20 HP unit doing the same work — that translates directly to longer service life and fewer rebuilds. You also get built-in backup: if one side goes down for service, the other keeps air moving.
Can one pump on the D10112HC3-S run independently if the other is down for maintenance?
Yes. Each pump on the D10112HC3-S has its own motor starter and unloader, so you can isolate one side and run the other solo. Output drops to roughly half capacity — one 10 HP pump feeding the 120-gallon tank — but for lighter demand loads you can stay operational while the other side gets serviced. Make sure your downstream demand doesn't exceed what the single pump can sustain before running in that configuration.
Does the D10112HC3-S include an alternator, and why does that matter?
The D10112HC3-S includes an automatic alternator that rotates lead-pump duty between the two 10 HP motors. Without alternation, one pump accumulates disproportionate hours and wears out faster — defeating the purpose of having two pumps. The alternator ensures both sides log comparable run time, which keeps wear even and makes maintenance intervals predictable for both pumps simultaneously.
What happens if one pump fails on the D10112HC3-S — does the compressor shut down completely?
No. The D10112HC3-S is wired so a fault on one motor starter doesn't take the entire unit offline. The functioning pump continues to operate and maintain tank pressure within its capacity. You'll need to address the failed side, but you're not dead in the water during a shift or a job. If you need help diagnosing a fault or sourcing parts for your D10112HC3-S, call us directly at 866-217-0063 — we're an authorized Cast Air dealer and can pull specs for your unit.
How does the maintenance schedule for the D10112HC3-S differ from a single-pump compressor?
Because the alternator splits run time between both pumps, each cast iron pump on the D10112HC3-S accumulates hours at roughly half the rate of a comparable single-pump unit running the same duty cycle — so oil changes, valve inspections, and belt checks are staggered by actual pump hours, not calendar time. Cast Air's all cast iron construction means the cylinders, heads, and crankcase hold up better between service intervals than aluminum-block alternatives. Track hours per pump individually; Cast Air recommends oil changes at 500 pump hours and full valve inspections at 2,000 pump hours under normal industrial use.
