8.2 Type II Recovery and Evacuation Procedures

8.2 Type II Recovery and Evacuation Procedures

Type II recovery and evacuation requirements are more detailed than Type I because high-pressure systems range from small residential units to large commercial installations with hundreds of pounds of refrigerant.

Evacuation Requirements for High-Pressure Systems

Before Opening for Service

Before opening a high-pressure or very high-pressure system for service (not just connecting gauges):

1. Recover refrigerant to the required evacuation level
2. For high/very high-pressure appliances: evacuate to 0 psig or below
3. Never open a system while it is under positive pressure (above 0 psig) — this would vent refrigerant

Recovery Procedure for Type II Systems

Step-by-step recovery procedure:

1. Identify the refrigerant — verify type from equipment nameplate or use a refrigerant identifier
2. Select appropriate recovery equipment — ensure it is rated for the refrigerant type and pressure
3. Connect recovery equipment — attach hoses to service ports (suction and/or liquid service valves)
4. Prepare the recovery cylinder — ensure it has capacity, is rated for the refrigerant, and is not over 80% full
5. Begin recovery — start the recovery machine; typically recover liquid first for speed, then switch to vapor recovery
6. Monitor progress — watch system pressure gauges and recovery cylinder weight
7. Complete to required level — continue until the required vacuum level is achieved
8. Isolate and verify — close valves and monitor for pressure rise (which indicates remaining refrigerant or a leak)

Liquid Recovery vs. Vapor Recovery

Push-Pull Recovery Method

For large systems (supermarkets, industrial installations), the push-pull method significantly speeds up recovery:

1. Connect the recovery machine to the system's vapor port
2. Connect a line from the recovery cylinder's liquid port back to the system's liquid line
3. The recovery machine creates a pressure differential
4. Liquid from the recovery cylinder is pushed through the system, displacing the remaining system liquid into the recovery cylinder
5. This method leverages liquid displacement for faster recovery

Oil Changes During Recovery

When changing compressor oil during service:

• Refrigerant must be recovered to reduce pressure to 5 psig or below before changing oil
• Changing oil at pressures above 5 psig is a violation (releases excessive refrigerant dissolved in oil)
• After oil change, evacuate the system before recharging

Charging Procedures

Liquid charging is required or recommended for:

• Zeotropic blends (R-407C, R-404A) — MUST be charged as liquid
• R-410A — should be charged as liquid per manufacturer guidelines
• Any time the system nameplate or manufacturer specifies liquid charging

Vapor charging is acceptable for:

• Single-component refrigerants (R-22, R-134a) when topped off
• Azeotropic blends

Important: When liquid charging through the suction (low) side, use a metering device or flow restrictor to prevent liquid slugging the compressor.

For the Exam: Know the push-pull method for large systems. Oil changes require reducing pressure to 5 psig or below. Zeotropic blends MUST be liquid charged. Always liquid-charge R-410A through the high side, or through the low side with a metering device to prevent liquid slugging.