The Castair BGAC3M is the compressor-mounted version of the BGAC3 belt guard aftercooler — rated at 75 CFM and built for reciprocating compressors in the 20 HP and larger class. The M designation means this unit ships configured for direct mounting to the compressor frame, as opposed to the BGAC3 loose unit which is installed independently. The core performance is identical: 75 CFM capacity, 1" NPT connections, 250 PSIG maximum pressure, and the ability to cool discharge air to within 15°F above ambient while removing up to 65% of moisture from the airstream.
If you are ordering a Castair compressor with aftercooling integrated into the assembly, or replacing an existing mounted aftercooler on a 20 HP or larger unit, the BGAC3M is the correct part. For standalone field installations or retrofit applications, the BGAC3 loose unit is the correct choice.
What an Aftercooler Does and Why It Matters at 20 HP and Above
A reciprocating compressor at 20 HP or larger produces substantial heat in the discharge air — temperatures at the pump head routinely reach 250°F. At that temperature, water vapor stays suspended in the airstream. Without an aftercooler intercepting it at the source, that moisture rides the hot air into the tank, corrodes the interior, and continues downstream through the distribution lines into tools, valves, cylinders, and spray equipment.
The BGAC3M mounts within the belt guard assembly and intercepts the discharge air before it reaches the tank. Ambient shop airflow — from the compressor flywheel or a dedicated fan — passes over the finned core and drops the air temperature rapidly. Water vapor condenses, collects at the bottom of the aftercooler, and drains away. What passes through to the tank is cooler and significantly drier.
- Temperature reduction: Cools compressed air to within 15°F above ambient temperature
- Moisture removal: Eliminates up to 65% of water content before it reaches the tank and distribution system
- No cooling water connection: Air-to-air design — only connections are the 1" NPT air inlet and outlet
- Tank corrosion protection: Moisture kept out of the tank extends tank service life substantially
- Downstream equipment protection: Cooler, drier air reduces wear and water damage to pneumatic tools, valves, and cylinders
Design and Construction
- Compressor-mounted configuration: Ships ready for direct mounting to the Castair compressor frame — the M suffix distinguishes this from the BGAC3 loose unit
- Belt guard integration: Mounts within the belt guard structure for a compact, protected installation
- 1" NPT connections: Standard 1" NPT inlet and outlet matching the discharge plumbing of 20 HP and larger reciprocating compressors
- High-pressure rating: 250 PSIG maximum operating pressure — handles the full output pressure of industrial reciprocating compressors
- High-temperature rating: 350°F maximum operating temperature — rated for the actual discharge temperatures produced by larger pump heads
- Performance basis: All ratings tested at 250°F inlet air temperature — real compressor discharge conditions, not laboratory ambient
Technical Specifications
- SKU: BGAC3M
- CFM Rating: 75 CFM
- Dimensions: 24" L x 20-1/2" W
- Weight: 20 lbs
- Inlet Connection: 1" NPT
- Outlet Connection: 1" NPT
- Maximum Operating Pressure: 250 PSIG
- Maximum Operating Temperature: 350°F
- Outlet Temperature: Within 15°F of ambient
- Moisture Reduction: Up to 65%
- Performance Basis: 250°F inlet air temperature
- Configuration: Compressor-mounted (M suffix)
- Base Model: BGAC3
- Compressor Fit: 20 HP and larger reciprocating compressors
- Manufacturer: Cast Air (Castair)
Available Configurations — BGAC Series Aftercooler Lineup
Castair produces the BGAC series in four sizes, each sized for a different compressor output range. Each size is available in both a loose unit and a compressor-mounted version.
- BGAC1 / BGAC1M: 35 CFM — 18" x 10-1/2", 3/4" NPT connections, 8 lbs — fits 5, 7, and 10 HP compressors
- BGAC2 / BGAC2M: 50 CFM — 18" x 14-1/4", 1" NPT connections, 12 lbs — fits 15 HP compressors
- BGAC3 / BGAC3M: 75 CFM — 24" x 20-1/2", 1" NPT connections, 20 lbs — fits 20 HP and larger compressors (this unit)
- BGAC4 / BGAC4M: 100 CFM — 23" x 26-1/2", 1" NPT connections, 25 lbs — for high-output systems above 75 CFM
The BGAC3 is the loose unit. The BGAC3M is this compressor-mounted version. If you are replacing an existing mounted aftercooler, confirm whether your original unit was the M configuration before ordering. Call 866-217-0063 if you need help confirming which version you have.
When Does a Shop Need the BGAC3M vs. the BGAC3 or Another Size?
The BGAC3M is the correct part when you need a 75 CFM aftercooler that ships in a compressor-mount configuration. Common scenarios:
- Compressor assembly order: You are ordering a Castair compressor and need the aftercooler to come pre-mounted — the M version is the right configuration
- Direct replacement: The existing BGAC3M on your compressor is damaged and needs replacement — order the same M configuration
- Original compressor spec: Your Castair unit was built with the BGAC3M from the factory — the M configuration ensures correct mounting alignment and bracket fitment
If you are doing a field retrofit installation and the aftercooler will be independently mounted rather than on the compressor frame, the BGAC3 loose unit is the more flexible option. If your compressor produces more than 75 CFM, move up to the BGAC4M. Call us to confirm the right configuration for your installation.
Why Buy From Air Compressor Factory Direct?
We have been specializing in air compressor parts, components, and accessories since 2016. We stock the full Castair BGAC series in both loose unit and compressor-mounted configurations. When you call, you reach someone who can confirm whether you need the BGAC3 or BGAC3M for your specific application — not a general order line.
- Free shipping on qualifying orders
- Free technical support at 866-217-0063 — fitment confirmation before you order
- Full manufacturer warranty on all Castair products
- Honest guidance — if the BGAC3 loose unit works better for your installation, we will tell you
Call 866-217-0063 for quick answers and help!
