Non-condensable gases are atmospheric gases like nitrogen and oxygen that enter the refrigeration system and cannot be liquefied under normal operating pressures. These gases increase system pressure and reduce cooling capacity by occupying space meant for refrigerant. Common sources include improper evacuation, component leaks, and contaminated refrigerant.
System Effects
Non-condensable gases cause high head pressure readings, typically 25-50 PSI above normal operating range. They reduce the effective cooling surface area in the condenser coil, forcing the compressor to work harder and consume more electricity. A system with just 5% non-condensable gas contamination can lose 5-10% of its cooling capacity.
Detection and Correction
Technicians identify non-condensable gas contamination through elevated head pressure that doesn’t match ambient temperature or by analyzing system pressure with a temperature-pressure chart. Correction requires complete system evacuation to at least 500 microns using a quality vacuum pump, followed by proper refrigerant charging. Persistent high pressure after evacuation indicates a slow leak requiring repair.