EPA 608 Type II: High-Pressure Systems
Know the Type II evacuation levels, leak repair rules, recovery techniques and safety points for high-pressure and very-high-pressure appliances.
Table of contents
Type II is the card most HVAC technicians use every day. It covers residential air conditioners and heat pumps, most rooftop units and most commercial refrigeration. The exam focuses on required recovery levels, when an appliance must be evacuated, how to speed up recovery and how to protect the system from moisture and air.
What You Will Be Able to Do
- State which equipment Type II covers.
- Use the required recovery level table.
- Decide when a repair is a major repair.
- Handle a leaking appliance that cannot reach the required level.
- Recover faster and avoid common mistakes on large systems.
What Type II Covers
Type II covers high-pressure, medium-pressure and very-high-pressure appliances, except small appliances and motor vehicle AC.
| Class | Saturation pressure at 104°F | Common refrigerants |
|---|---|---|
| High-pressure | 170 to 355 psia | R-22, R-410A |
| Medium-pressure | 45 to 170 psia | R-134a, R-12 |
| Very-high-pressure | Above 355 psia, or critical temperature below 104°F | R-13, R-23 |
Newer residential refrigerants such as R-32 and R-454B also fall under Type II.
Required Recovery Levels
Before opening or disposing of an appliance, you must recover refrigerant down to the level in this table. The level depends on the appliance and when the recovery equipment was made. Levels are in inches of mercury vacuum.
| Appliance | Recovery equipment made before Nov 15, 1993 | Made on or after Nov 15, 1993 |
|---|---|---|
| Very-high-pressure | 0 | 0 |
| High-pressure, under 200 lb | 0 | 0 |
| High-pressure, 200 lb or more | 4 | 10 |
| Medium-pressure, under 200 lb | 4 | 10 |
| Medium-pressure, 200 lb or more | 4 | 15 |
Worked example: you recover an R-134a chiller with a 300 lb charge, using a 2020 machine. It is a medium-pressure appliance at 200 lb or more, so you must reach 15 inches of vacuum.
Worked example: you recover a 12 lb R-410A split system. It is a high-pressure appliance under 200 lb, so the level is 0 inches, meaning atmospheric pressure. In practice, many technicians pull a little lower so the refrigerant does not rebound.
After you reach the level, wait a few minutes. If pressure rises, refrigerant is still boiling off, and you need to recover again.
Major and Non-Major Repairs
A major repair involves removing the compressor, condenser, evaporator or an auxiliary heat exchange coil. It also includes uncovering more than 4 square inches of flow area for more than 15 minutes.
For a major repair, or for disposal, you must reach the required level in the table. For a non-major repair that is not followed by evacuation, you may stop at 0 psig.
When the Appliance Leaks
If leaks make it impossible to reach the required level, isolate the leaking part if you can and evacuate the non-leaking part to the required level. If you cannot isolate it, evacuate to the lowest level you can reach, and no higher than 0 psig.
Recovery Technique
- Recover liquid first. Liquid moves faster than vapor. On large systems, use push-pull or draw liquid from the receiver or the liquid line.
- Recover from both sides. Hooking up to the high and low sides shortens the job, and it avoids trapping refrigerant behind a closed valve or a solenoid.
- Watch for trapped pockets. Solenoid valves and check valves can hold refrigerant.
- Cool the cylinder on a hot day. A cooler cylinder takes refrigerant faster.
- Protect water-cooled equipment. On a chiller, keep water moving through the tubes during recovery, so that falling refrigerant temperature does not freeze the water and burst a tube.
- Stop at 80% by weight in each cylinder.
- Use the right machine. Recovery equipment must be certified, and it must match the refrigerant, including A2Ls.
System-dependent recovery is not allowed on appliances with a full charge over 15 lb.
Keeping Moisture and Air Out
- Moisture forms acids and can freeze at the metering device. A filter-drier catches a small amount, and a deep vacuum removes the rest.
- Non-condensables such as air raise head pressure. They get in through open lines and poor evacuation.
- Leak tests use dry nitrogen through a regulator, never oxygen or compressed air. Use the test pressure on the data plate.
- Dehydration needs a deep vacuum, with the pump isolated before the final reading. Use a micron gauge.
Signs of a leak on a high-pressure system include oil at a joint and excessive superheat. Signs of air in the system include high head pressure with normal subcooling.
Leak Repair Reminders
Under Part 84, appliances with 15 lb or more of an HFC or substitute with a GWP above 53 have leak limits, except residential and light commercial AC and heat pump appliances. Ozone-depleting refrigerants such as R-22 are covered under Part 82 at 50 lb or more. Limits are 10% a year for comfort cooling, 20% for commercial refrigeration and 30% for industrial process refrigeration. Repair within 30 days and run a follow-up verification test within 10 days.
Safety Reminders
Warning: Do not run a compressor or energize it during a deep vacuum. Keep your face away from hose connections, and wear eye protection and gloves when handling liquid refrigerant.
Large mechanical rooms need ventilation and working refrigerant alarms. ASHRAE 15 is the common standard for machine rooms.
Exam Format
Type II has 25 questions and is closed book, with a proctor. Passing takes 70%, or 18 of 25 in practice. You also need Core.
Common Mistakes
| Mistake | What it costs |
|---|---|
| Using the same level for every system | A wrong answer, and a violation on the job |
| Reading the date on the appliance, not on the machine | A wrong level |
| Forgetting that R-134a is medium-pressure | The wrong row of the table |
| Recovering a chiller with water off | A burst tube and a huge repair |
| Stopping at the target without checking for rebound | Refrigerant still in the system |
Check Your Understanding
You are replacing a compressor on a 220 lb R-22 system. Your recovery machine was built in 2018. What level must you reach? 10 inches of vacuum. R-22 is high-pressure, the charge is over 200 lb, and the machine is new.
A coil has a hole, and you cannot isolate it. You cannot reach the required level. What do you do? Evacuate to the lowest level you can reach, and no higher than 0 psig.
You are replacing a Schrader core and do not plan to evacuate. How low must you go? 0 psig, since that is a non-major repair not followed by evacuation.
Why do you recover liquid first on a large system? It is much faster than pulling vapor.
Key Takeaways
- Type II covers high, medium and very-high-pressure appliances.
- Under 200 lb, high-pressure systems recover to 0 inches, and medium-pressure systems recover to 10 inches with newer equipment.
- At 200 lb or more, high-pressure systems recover to 10 inches, and medium-pressure systems to 15 inches with newer equipment.
- Major repairs involve the compressor, condenser, evaporator or auxiliary coil.
- A leaking appliance that cannot reach the level must still go to the lowest level you can reach, no higher than 0 psig.
- Keep water moving during chiller recovery, and fill cylinders only to 80%.