6.3 Required Levels of Evacuation

Evacuation: How Deep You Must Pull the Vacuum

Recovering refrigerant is not just "get most of it out." Before a system is opened for service, repair, or disposal, the technician must pull it down to a specific, legally required level of evacuation, measured in inches of mercury vacuum (in. Hg) for higher-pressure systems or millimeters of mercury absolute (mm Hg absolute) for low-pressure systems. EPA publishes these targets in Table 2 — Required Levels of Evacuation, and reproducing it from memory is one of the most valuable things you can do for the exam. Multiple questions across Core, Type II, and Type III draw directly from this table.

The required depth depends on three variables: (1) the appliance pressure class (very high, high, medium, or low pressure), (2) the charge size (under 200 lb vs. 200 lb or more), and (3) whether the recovery equipment was made before or on/after November 15, 1993. Newer equipment must reach deeper vacuums because it is capable of doing so.

Why a Deeper Vacuum?

Pulling a deeper vacuum does two jobs at once: it satisfies federal law by removing essentially all the refrigerant, and it removes moisture and non-condensable gases that would otherwise corrode the system and form acids. So the evacuation requirement protects the planet and the equipment.

EPA Table 2 — Equipment Made ON OR AFTER November 15, 1993

EPA Table 1 — Equipment Made BEFORE November 15, 1993

Reading the Table the Way the Exam Tests It

Notice the pattern. For older (pre-1993) equipment the deeper requirement caps out at 4 in. Hg for the larger high/medium-pressure systems. For newer (post-1993) equipment those same large systems must be pulled to 10 in. Hg (high-pressure ≥ 200 lb and medium-pressure < 200 lb) or 15 in. Hg (medium-pressure ≥ 200 lb). The four numbers worth burning into memory for new equipment are therefore 0, 10, 15, and 25 mm Hg absolute.

Special Rules by Pressure Class

• Very high-pressure appliances (which operate far above atmospheric) are evacuated only to 0 psig — you may not vent them above atmospheric pressure, but no deep vacuum is required.
• Low-pressure appliances (which normally operate below atmospheric) require a true deep vacuum of 25 mm Hg absolute with new equipment — a very low absolute pressure — because that is how you confirm essentially all the low-pressure refrigerant is out.

When You Cannot Reach the Required Level

Sometimes a leak or equipment limitation makes the table value unreachable. EPA provides a fallback procedure:

1. Isolate the leak if it is possible to do so.
2. Evacuate the appliance to the lowest level achievable without substantially contaminating the refrigerant.
3. You may never discharge refrigerant above 0 psig before opening the system, regardless of pressure class.

A related point: when an appliance is disposed of, the same recovery/evacuation requirements apply, and the last person in the disposal chain is responsible for ensuring recovery was completed.

Putting It Together

Example: A technician services a 300-pound R-22 (high-pressure) chiller using a recovery machine manufactured in 2019. Step 1 — confirm the pressure class: R-22 is high-pressure. Step 2 — check the charge: 300 lb is ≥ 200 lb. Step 3 — the equipment is post-1993. Reading Table 2, the required evacuation is 10 in. Hg vacuum. If the technician instead pulled only to 0 psig, the system would not be legally evacuated, because high-pressure systems of 200 lb or more on new equipment must reach 10 in. Hg.

Contrast Example: The same technician next services an R-11 low-pressure centrifugal chiller. Pressure class is low-pressure, so charge size is irrelevant — the requirement is 25 mm Hg absolute, a deep vacuum, with that post-1993 machine.

For the Exam: Memorize the post-1993 set — very high-pressure and small high-pressure: 0 psig; high-pressure ≥ 200 lb and medium-pressure < 200 lb: 10 in. Hg; medium-pressure ≥ 200 lb: 15 in. Hg; low-pressure: 25 mm Hg absolute. And remember the dividing line is November 15, 1993.