The Low Pressure Category includes HVAC systems and large appliances using refrigerants that operate at pressures below 10 pounds per square inch (psi) in the low-side circuit. These systems typically use chlorofluorocarbon (CFC) refrigerants like R-11 or hydrochlorofluorocarbon (HCFC) refrigerants like R-123. Low-pressure systems require specialized servicing equipment and Type II certification.
Technical Characteristics
Low-pressure systems operate with saturation pressures below 10 psi at 104°F and include centrifugal chillers and large commercial air conditioning equipment. These systems are prone to atmospheric contamination due to low operating pressures. Technicians must maintain strict protocols to prevent moisture and non-condensable gases from entering the system during service work.
Service Protocols
Type II certification covers low-pressure equipment servicing. Technicians must understand evacuation procedures, leak detection methods, and proper recovery techniques specific to low-pressure systems. Field servicing typically requires portable recovery equipment meeting EPA specifications. Most low-pressure CFC systems are being phased out in favor of high-efficiency alternatives.