Refrigeration Systems and Refrigerant Piping
This domain tests refrigeration systems and refrigerant piping: refrigerant classification, materials, brazing, pressure testing, evacuation, leak detection, relief devices, ventilation, machinery rooms, supports, and protection.
Core rules
- Refrigerants are classified by safety group, including toxicity and flammability. The classification affects charge limits, ventilation, detection, and occupancy restrictions.
- Refrigerant piping must be approved for the refrigerant and pressure, supported, protected from damage, and installed with proper slope and oil return where required. Flexible connections must be listed for the application.
- Brazing requires an inert purge to prevent internal oxidation. Pressure testing uses dry nitrogen or another approved inert gas, never oxygen or flammable gas. Evacuation must meet the manufacturer's micron level.
- Relief devices and relief piping must be sized and terminated safely. Machinery rooms may require ventilation, detection, or emergency controls depending on refrigerant and charge.
- Leak testing and charging must follow manufacturer procedures; overcharging or adding refrigerant without correcting a leak is unacceptable.
Worked example
A split system using R-410A is being pressure tested. The technician proposes using oxygen because it is available and will show leaks. This is prohibited and dangerous. The correct method is dry nitrogen pressure testing at the listed test pressure, followed by leak detection, repair, evacuation to the manufacturer's micron level, and charging by weight or subcooling/superheat as instructed.
Traps
Using oxygen for pressure testing; skipping nitrogen purge during brazing; ignoring A2L or higher-toxicity refrigerant rules; terminating relief piping where it can injure someone; and failing to support or protect refrigerant lines.