Universal candidates have to move between three very different equipment categories after Core.

The fastest way to create confusion is to memorize a pressure, percentage, or recovery technique without first asking:

Which type of appliance is this question about?

Type I: small appliances

Type I is narrower than “small air conditioner” or “anything under five pounds.”

The book emphasizes the EPA definition: the appliance must fit the specified category and be fully manufactured, charged, and hermetically sealed in a factory with five pounds or less of refrigerant.

High-yield Type I distinctions include:

  • 80% recovery when the compressor is not functional or recovery/recycling equipment is pre-November 15, 1993;
  • 90% recovery when post-1993 recovery/recycling equipment is used and the compressor is functional;
  • 4 in Hg vacuum as an alternative compliance route described in the book;
  • operating a functional compressor when using system-dependent recovery;
  • accessing both high and low sides when the compressor is inoperative;
  • removing temporary solderless access fittings at the end of service.

Type I questions often test whether you have attached the recovery rule to both the equipment era and the compressor condition.

Type II: high- and very-high-pressure appliances

Type II combines more moving parts:

  • appliance pressure class;
  • full charge above or below 200 pounds;
  • pre- or post-November 15, 1993 recovery equipment;
  • major versus non-major repair;
  • leak-repair scope;
  • recovery technique;
  • pressure rebound and safety.

The book’s current service-practice summary uses these high-confusion rows:

  • high pressure under 200 lb: 0/0;
  • high pressure 200+ lb: 4/10;
  • medium pressure under 200 lb: 4/10;
  • medium pressure 200+ lb: 4/15;
  • very high pressure: 0/0.

The two values in each pair correspond to pre-1993 and post-1993 recovery equipment.

Type II also contains the leak-repair framework described in the book for appliances with at least 50 pounds of ozone-depleting refrigerant, including the current 30/20/10/10 trigger pattern, normal 30-day repair period, the 120-day industrial-process-shutdown case, and initial plus follow-up verification testing.

Type III: low-pressure appliances

Type III reverses several instincts from positive-pressure systems.

Low-pressure chillers commonly operate below atmospheric pressure, so a leak can pull air and moisture into the machine.

That is why excessive purge-unit operation is a classic clue.

The book highlights:

  • 25 mm Hg absolute as the low-pressure recovery endpoint;
  • controlled hot water or built-in heating/pressurization as the preferred first approach in the Type III test-topic outline for raising pressure for leak checking;
  • continuing vapor recovery after visible liquid is gone;
  • heating chiller oil to 130 F before removal;
  • circulating or removing water during deep evacuation to reduce freezing risk;
  • introducing refrigerant vapor before liquid during recharge;
  • using the evaporator charging valve for the centrifugal-chiller charging concept in the Type III outline.

The unit wording matters: 25 millimeters Hg absolute is not 25 inches Hg vacuum.

The fastest section check

When you see a question, identify the equipment first.

Clue Think
Factory-made/charged/hermetically sealed, five pounds or less Type I
High- or very-high-pressure equipment, evacuation table, leak-repair framework Type II
Low-pressure chiller, purge unit, 25 mm Hg absolute Type III

Then attach the number or procedure to that equipment class.

Where Core fits

Core is not a fourth appliance category.

It is the shared foundation: certification scope, environmental concepts, recovery/recycle/reclaim, venting, sales restrictions, safety, pressure units, cylinders, nitrogen, blends, substitute refrigerants, and recordkeeping concepts.

For a full study sequence, use the 14-day Universal study plan.