Type II: High-Pressure Appliances
Type II certification covers high-pressure and very-high-pressure appliances, from residential split systems to supermarket racks. This chapter defines the high-pressure category, lists the required evacuation levels, and reviews the leak-detection and recovery techniques you will use on these systems.
High-Pressure Appliances Defined
A high-pressure appliance uses a refrigerant with a boiling point between roughly minus 50°F and 10°F at atmospheric pressure, which means it operates at positive pressure well above atmospheric. Common high-pressure refrigerants include HCFC-22, HFC-410A, HFC-404A, HFC-407C, CFC-12, and CFC-500. A separate very-high-pressure category covers refrigerants such as R-13 and R-503 that boil below about minus 50°F. Type II certification is required to service, maintain, repair, or dispose of these medium-, high-, and very-high-pressure appliances, except for small appliances and motor-vehicle air conditioners, which fall under Type I and Section 609 respectively. Most everyday HVAC and commercial refrigeration work is Type II, so this is the certification most field technicians rely on daily.
Evacuation Levels for High-Pressure Systems
Before opening a high-pressure appliance for major service or disposal, you must recover refrigerant to a required vacuum that depends on the appliance size and the age of your recovery equipment. Using recovery equipment manufactured on or after November 15, 1993, the required levels in inches of mercury vacuum are: for HCFC-22 appliances, 0 in Hg if under 200 pounds and 10 in Hg if 200 pounds or more; for other high-pressure appliances such as those using CFC-12, 10 in Hg if under 200 pounds and 15 in Hg if 200 pounds or more; and for very-high-pressure appliances, 0 in Hg. Older recovery equipment made before that date generally requires only 0 or 4 in Hg. These figures are heavily tested, so associate each refrigerant and size with its number.
Leak Detection Methods
Finding leaks quickly protects the charge, the equipment, and the atmosphere. An electronic leak detector is highly sensitive and pinpoints small leaks by sensing refrigerant near a joint. A soap-bubble solution brushed on a suspect fitting reveals larger leaks as growing bubbles. A fluorescent dye added to the system shows leak points under ultraviolet light after the unit runs. An ultrasonic detector hears the hiss of escaping gas. To pressurize a system for leak testing, use dry nitrogen, sometimes with a trace of refrigerant so an electronic detector can sense it, but never use oxygen or compressed air. Always leak-test and repair a system before recharging it, because charging a leaking system simply vents refrigerant and wastes money.
Recovery Techniques for High-Pressure Systems
Recovering a high-pressure system efficiently means managing both liquid and vapor. On a large charge, recover liquid first through the liquid-line port to move the bulk quickly, then switch to vapor recovery to pull the remaining gas down to the required vacuum. Recovering liquid before vapor greatly shortens the job. Non-condensable gases such as air raise head pressure and slow recovery, so purge them and avoid drawing air into the system. Keep hoses short and use low-loss fittings to minimize the refrigerant released when you connect and disconnect. Watch the recovery cylinder weight and never exceed 80 percent fill. If the appliance is very cold or the ambient is low, recovery slows, so warming the appliance slightly or cooling the recovery cylinder can speed the transfer.
Last updated: July 2026