The Castair AC120 Free Standing Aftercooler is a purpose-built heat exchanger that mounts in the discharge line between your compressor and the receiver tank. Its job is simple but critical: cool the hot, moisture-laden compressed air coming off the pump before it enters your tank and air lines. Hot compressed air holds water vapor in suspension — the moment that air cools down, the moisture drops out as liquid condensate. Do that cooling before the tank instead of inside the tank, and you catch the water at one controlled point with a drain, instead of letting it spread through 200 feet of air piping into your tools, guns, and equipment.
The AC120 handles 120 CFM at up to 250 PSIG and up to 350°F inlet air temperature, making it the right fit for compressor systems in the 25–40 HP range that discharge at the temperatures and pressures typical of two-stage reciprocating and rotary screw machines. Every shop that sprays paint, runs air-powered precision equipment, or uses a refrigerated dryer downstream needs to understand one fact: your air dryer works significantly better when the air arrives pre-cooled. An aftercooler is not optional equipment for a serious compressed air system — it is the first stage of your air treatment train.
Why Hot Compressed Air Destroys Shop Equipment
A two-stage reciprocating compressor discharges air at 250–350°F. At that temperature, the air is carrying all the water vapor it can hold in suspension. When that superheated air hits your receiver tank and cools to ambient conditions, it releases moisture — inside the tank. That condensate sits on the tank floor, promotes rust, and every time you open a tool or air gun, you are pulling water-saturated air through it. Over months, water ruins:
- Paint and clear coat jobs: water in the air line causes fisheye, blushing, and adhesion failure
- Air-powered precision tools: moisture corrodes internal bearings, vanes, and rotors
- Pneumatic controls and automation: water in solenoid valves and actuators causes sticking, leaking, and failure
- Refrigerated air dryers: dryers sized for 70°F inlet air become overwhelmed when fed 120°F air from a hot tank; they cannot keep up and pass wet air downstream
An aftercooler solves all of these problems at the source. Cool the air before the tank, remove the moisture with a drain, and everything downstream — dryers, filters, tools, spray guns — works correctly and lasts longer.
Key Features of the AC120 Aftercooler
- 120 CFM Capacity: Rated for compressed air systems producing up to 120 CFM — sized for 25–40 HP compressor packages typical in busy auto repair shops, body shops, and fleet facilities
- 250 PSIG Maximum Pressure: Handles the full pressure range of two-stage reciprocating and rotary screw compressors without restriction
- 350°F Maximum Inlet Air Temperature: Engineered to accept the hottest discharge air from industrial compressor pumps without damage or performance loss
- Cools to Within 15°F of Ambient: The AC120 brings compressed air temperature down to within 15 degrees of the ambient shop temperature — if your shop is 70°F, your air exits at approximately 85°F or less
- 65% Total Water Reduction: Removes approximately 65% of the total water vapor load from the compressed air stream before it reaches your tank — every 20-degree temperature drop removes 50% of remaining moisture
- 1-1/2 inch NPT Inlet and Outlet Ports: Standard NPT connections for straightforward integration into existing discharge piping
- Fan-Cooled Heat Exchanger: Electric fan drives ambient air across the heat exchanger core — no water connection required, no water treatment, no drain-back concerns
- 115V / 1-Phase / 60 Hz Power: Standard single-phase power for the cooling fan — plug into any standard shop outlet
- Floor or Suspended Mounting: Mount it upright on the floor next to the compressor, or hang it from overhead structure to save floor space
- Horizontal or Vertical Air Flow: Configurable for your installation layout
- Dimensions: 43.5 inches H x 14.75 inches W x 46.5 inches D
- Weight: 140 lbs
- Minnesota-Built: Castair manufactures in Minnesota to industrial-grade standards built for long service life in demanding environments
What is in the Box
- Castair AC120 free standing aftercooler unit
- Fan assembly and motor (pre-installed)
- 1-1/2 inch NPT inlet and outlet fittings
- Mounting hardware for floor installation
- Installation documentation
Optional accessories available separately: filter with automatic drain, temperature control valve #86816.
Available Configurations — Full Castair Free Standing Aftercooler Lineup
Castair produces a complete range of free standing aftercoolers to match compressors from small single-phase units to large industrial two-stage machines. Match the aftercooler CFM rating to your compressor's rated output CFM:
- FSAC35: 35 CFM, 3/4 inch NPT — for small single-phase compressors, 5–7.5 HP
- FSAC50: 50 CFM, 1 inch NPT — for 7.5–10 HP compressor packages
- FSAC75: 75 CFM, 1 inch NPT — for 10–15 HP units
- FSAC100: 100 CFM, 1-1/4 inch NPT — for 15–25 HP compressors
- AC120: 120 CFM, 1-1/2 inch NPT — for 25–40 HP compressors (this unit)
- AC150: 150 CFM, 1-1/2 inch NPT — for 40–50 HP compressors
- AC240: 240 CFM, 2 inch NPT — for 50–75 HP industrial compressors
- AC300: 300 CFM, 2 inch NPT — for 75–100 HP large industrial systems
All models share the same 250 PSIG / 350°F maximum ratings and 15°F approach temperature performance. Contact us if you need help sizing the right model for your compressor output.
Belt Guard Style Aftercoolers — Alternative Mounting Option
Castair also offers belt guard-mounted aftercoolers that install directly on the compressor in place of the belt guard — a compact solution for installations where floor or ceiling space is limited:
- BGAC1: 35 CFM — for small belt-drive compressors
- BGAC2: 50 CFM
- BGAC3: 75 CFM
- BGAC4: 100 CFM
Belt guard models top out at 100 CFM. At the AC120 capacity level, the free standing unit is the correct choice.
When Does a Shop Need the AC120?
The AC120 is sized for compressors producing 100–120 CFM — typically 25–40 HP two-stage reciprocating units or equivalent rotary screw compressors. This covers a wide range of serious shop installations:
- Multi-bay auto repair shops running 3–5 lifts, multiple impact wrenches, and air ratchets simultaneously from one compressor header
- Body shops and collision repair facilities where air quality directly determines paint finish quality — one bad job traced to wet air costs more than an aftercooler
- Fleet maintenance operations running tire equipment, air tools, and pneumatic lifts across multiple bays continuously
- Machine shops running air-powered precision equipment, air chucks, and coolant blow-off where moisture causes surface contamination
- Any shop with a refrigerated air dryer — an aftercooler upstream reduces the dryer's load dramatically and keeps it working correctly even when the shop is hot in summer
If your compressor is under 100 CFM, step down to the FSAC100. If your compressor produces over 120 CFM, step up to the AC150 or AC240. Oversizing an aftercooler is not harmful, but undersizing one means it cannot keep up at peak demand.
Technical Specifications
- Model: AC120
- Manufacturer: Castair (Cast Air) — Minnesota, USA
- Capacity: 120 CFM
- Maximum Working Pressure: 250 PSIG
- Maximum Inlet Air Temperature: 350°F
- Approach Temperature: Within 15°F of ambient air temperature
- Water Removal: Approximately 65% of total moisture load (based on 250°F inlet air)
- Port Size: 1-1/2 inch NPT (inlet and outlet)
- Power Supply: 115V, 1-phase, 60 Hz
- Mounting Options: Floor standing or suspended overhead
- Air Flow Orientation: Horizontal or vertical
- Dimensions: 43.5 inches H x 14.75 inches W x 46.5 inches D
- Weight: 140 lbs
- Performance Basis: Specifications based on 250°F inlet air temperature at rated CFM
Optional Accessories
- Filter with Automatic Drain: Captures and automatically purges condensate collected at the aftercooler outlet — eliminates manual drain intervals
- Temperature Control Valve #86816: Modulates cooling fan operation to maintain consistent outlet air temperature — useful in cold climates to prevent overcooling and freeze-up in winter months
Why Buy From Air Compressor Factory Direct?
Air Compressor Factory Direct has been supplying commercial and industrial compressed air equipment since 2016. We are not a general hardware retailer — we specialize in compressed air systems and the people who buy from us are shop owners, maintenance managers, and facilities engineers who need the right equipment the first time. When you call us, you reach someone who can discuss your compressor model, your shop load, your downstream air treatment, and tell you exactly which aftercooler fits your installation.
- Free Shipping: Every Castair aftercooler ships free to the continental US
- Free Pre-Sale Technical Support: Call us before you order — we will verify sizing, mounting options, and accessory requirements for your specific compressor
- Full Manufacturer Warranty: All Castair equipment carries full factory warranty coverage
- Honest Guidance: If the AC120 is not the right size for your compressor, we will tell you — and point you to the model that is
- Castair Specialist: We stock the full Castair aftercooler lineup and can answer model-specific questions
Call 866-217-0063 for quick answers and help!
