Cools compressed air to ~38°F so water vapor condenses and is drained off. Most shop air systems use a refrigerated dryer.
How it works
Compressed air enters the air-to-air pre-cooler, then an evaporator chilled by a small refrigeration circuit. Water drops out at the moisture separator. Air leaves at ~37–50°F pressure dewpoint (PDP).
Key specs
- Typical PDP38–50°F
- Inlet temp max120°F (check nameplate)
- Ambient max100°F typical
- Pressure drop3–5 psid clean
Sizing
- Size to inlet CFM at worst-case inlet temperature (often 100°F) and operating pressure.
- Derate factor: for every 5°F above 100°F inlet, capacity drops ~10–15%.
- Pressure derate: at 80 psig, capacity is ~80% of 100 psig rating.
- Add 25–50% headroom for future demand and recovery from upsets.
Installation
- Bypass loop with 3-valve arrangement so dryer can be serviced without dropping plant air.
- Pre-filter (general purpose, 5 µm) upstream; coalescing filter downstream is optional.
- Leave 24" clearance on intake/exhaust louvers; high ambient = poor dewpoint.
- Drain piped to oil-water separator before disposal.
Preventive maintenance
- Weekly: verify drain cycling, check inlet/outlet pressure gauges, log dewpoint.
- Monthly: blow off condenser coil (vacuum or compressed air, screens out).
- Quarterly: clean strainer ahead of drain, verify hot-gas bypass setpoint (~35°F).
- Annual: leak-check refrigerant circuit, megger compressor windings.
Troubleshooting
Dewpoint too high (water at point of use)
Likely causes
- Dirty condenser coil → high head pressure → poor cooling
- Low refrigerant charge
- Failed solenoid / TXV / hot-gas bypass stuck open
- Plugged drain — separator flooded
- Oversized airflow vs dryer capacity
Fix
Clean condenser, verify charge/subcool, repair drain, confirm CFM and inlet temp are within rating.
High pressure drop across dryer
Likely causes
- Plugged pre-filter element
- Frozen evaporator (suction pressure too low)
Fix
Replace filter element; if evaporator freezing, check hot-gas bypass setpoint and refrigerant charge.