HVAC Exam Lab
Core, Type II and Type III

Evacuation levels

The table everyone loses marks on.

Why this one catches people

It is a table of numbers with two columns, two units pointing in opposite directions, and a date that changes the answer. There is nothing to reason out; you either know it or you guess.

35 questions in our bank map to this material, across 9 outline topics and 4 exam sections (Core (Group I): 4, Type I: Small Appliances: 8, Type II: High-Pressure Systems: 11, Type III: Low-Pressure Systems: 12).

The table

Required levels of evacuation before opening an appliance, from 40 CFR 82.156. The date column refers to when the recovery equipment was manufactured, not the appliance.

Type of applianceBefore 15 Nov 1993On or after 15 Nov 1993
Very high-pressure appliance00
High-pressure appliance, or isolated component, under 200 lb charge00
High-pressure appliance, or isolated component, 200 lb charge or more410
Medium-pressure appliance, or isolated component, under 200 lb charge410
Medium-pressure appliance, or isolated component, 200 lb charge or more415
Low-pressure appliance25 mm Hg absolute25 mm Hg absolute

Units. Every figure is inches of mercury vacuum except the low-pressure row, which is 25 mm Hg absolute. Those are different units measuring in opposite directions, and it is the single most common way to lose a mark on this table.

Small appliances are scored differently

Small appliances are not on the table above. They have their own rule, and it gives you a choice between a recovery percentage and a vacuum:

SituationRequirement
Recovery equipment made before 15 Nov 1993Recover 80% of the refrigerant
Equipment made on or after 15 Nov 1993, compressor workingRecover 90% of the refrigerant
Equipment made on or after 15 Nov 1993, compressor not workingRecover 80% of the refrigerant
Or, either wayEvacuate the appliance to four inches of mercury vacuum

The pattern is worth memorising as a shape rather than four separate facts: newer equipment demands more (90%), unless the compressor is dead, in which case you are back to 80% because the system cannot help you push refrigerant out.

Where people go wrong

  • Reading the low-pressure row in the same units as the rest. It is 25 mm Hg ABSOLUTE, not 25 inches of vacuum.
  • Forgetting the 200-pound line. The same appliance type has different requirements above and below it.
  • Applying the post-1993 column to older recovery equipment. The date refers to when the RECOVERY EQUIPMENT was manufactured.
  • Assuming very high-pressure equipment needs a deep vacuum. It requires 0.

Drill exactly this

35 questions in the bank cover this material. Anything you miss goes to your notebook so you can come back to it.

Quick practice drill

15 questions · 18 minutes · pass at 70%

Questions are sampled to mirror the official domain weighting. The timer starts when you begin; you can flag questions and return to them before submitting.

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