The Castair BGAC4M is the compressor-mounted version of the BGAC4 belt guard aftercooler — the largest unit in the BGAC series, rated at 100 CFM and configured for direct mounting to the compressor frame. The M designation differentiates this from the BGAC4 loose unit: the BGAC4M ships pre-configured for integration into the Castair compressor assembly, not as a field-install standalone unit. The core performance is the same — 100 CFM capacity, 1" NPT connections, 250 PSIG maximum pressure, cooling discharge air to within 15°F of ambient while removing up to 65% of moisture.
If you are ordering a Castair compressor with aftercooling built into the assembly at the top of the BGAC range, or replacing a failed BGAC4M on an existing compressor, this is the correct part. For standalone or field-retrofit installations, the BGAC4 loose unit is the more appropriate option.
What an Aftercooler Does at 100 CFM
Large reciprocating compressors generate substantial heat. At high output, discharge air temperatures at the pump head commonly reach 250°F. At that temperature, moisture stays suspended in vapor form and travels with the airstream into the tank, through distribution lines, and into downstream tools, valves, cylinders, and spray equipment. The BGAC4M stops that at the source.
Mounted within the belt guard assembly, the BGAC4M intercepts the discharge air immediately after the pump head. The large finned core — 23" x 26-1/2" — provides the cooling surface needed to bring 100 CFM of compressed air down to within 15°F of ambient temperature. Moisture condenses, collects, and drains before the air ever reaches the tank. What passes through the system is cooler, significantly drier air.
- Temperature reduction: Cools compressed air to within 15°F above ambient at 100 CFM rated flow
- Moisture removal: Eliminates up to 65% of water content before it reaches the tank and distribution system
- 100 CFM capacity: The largest aftercooler in the Castair BGAC series — sized for the highest-output reciprocating compressors in the lineup
- No cooling water connection: Air-to-air design — 1" NPT air inlet and outlet are the only connections required
- Compressor-mounted configuration: Integrates directly into the compressor frame assembly — no separate mounting or external plumbing runs
Design and Construction
- Compressor-mounted configuration: Ships ready for direct mounting to the Castair compressor frame — the M suffix distinguishes it from the BGAC4 loose unit
- Belt guard integration: Fits within the belt guard structure for a compact, factory-clean installation
- 1" NPT connections: Standard 1" NPT inlet and outlet — matches the discharge plumbing of high-output Castair reciprocating compressors
- 250 PSIG maximum operating pressure: Handles the full output pressure range of large industrial reciprocating compressors
- 350°F maximum operating temperature: Rated for the actual discharge temperatures produced by large-frame pump heads under sustained load
- Performance tested at 250°F inlet: All ratings verified at real compressor discharge conditions — not ambient test conditions
- Largest core in the series: At 23" x 26-1/2" and 25 lbs, the BGAC4 core provides the cooling surface needed for 100 CFM throughput
Technical Specifications
- SKU: BGAC4M
- CFM Rating: 100 CFM
- Dimensions: 23" L x 26-1/2" W
- Weight: 25 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: BGAC4
- Position in Series: Top tier — largest unit in the BGAC lineup
- Manufacturer: Cast Air (Castair)
Available Configurations — Full BGAC Series Lineup
Castair produces the BGAC series in four sizes. Each size is available as a loose unit and a compressor-mounted version (M suffix). The mounted versions are for compressor assembly integration; the loose units are for field installation and retrofits.
- 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
- BGAC4 / BGAC4M: 100 CFM — 23" x 26-1/2", 1" NPT connections, 25 lbs — top-tier unit for the highest-output systems (this unit)
The BGAC4 is the loose unit. The BGAC4M is this compressor-mounted version. If you are replacing an existing mounted aftercooler, verify whether the original was the M configuration before ordering — a loose BGAC4 requires different mounting than the BGAC4M. Call 866-217-0063 to confirm before you order.
When Does a Shop Need the BGAC4M vs. the BGAC4 or a Smaller Unit?
The BGAC4M is the right part in these specific situations:
- Compressor assembly with integrated aftercooling: Ordering a new Castair compressor configured with a top-tier aftercooler as part of the assembly — the M version ensures proper mounting alignment and bracket fitment
- Direct replacement for an existing BGAC4M: The original mounted aftercooler has failed — the M configuration is required to match the existing mounting hardware
- Factory-spec installations: Some Castair compressor models specify the BGAC4M in the original build documentation — use the same configuration to maintain factory specs
If you are doing a field retrofit on an existing compressor and mounting the aftercooler independently — not to the compressor frame — the BGAC4 loose unit gives you more installation flexibility. If your compressor output is within the 75 CFM range, the BGAC3M may be the more appropriate size. Call us with your compressor model and we can confirm the right configuration and size before you order.
Why Buy From Air Compressor Factory Direct?
We have been specializing in air compressor parts, components, and accessories since 2016. We carry 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 BGAC4 or BGAC4M, and whether the BGAC4 is the right size for your compressor — not a call center reading from a product list.
- Free shipping on qualifying orders
- Free technical support at 866-217-0063 — fitment and configuration confirmation before you order
- Full manufacturer warranty on all Castair products
- Honest guidance — if the BGAC3M is the correct size for your compressor, we will say so
Call 866-217-0063 for quick answers and help!
