Type II: High‑Pressure Appliances

EPA Section 608 Study Guide · Type II Section (25 questions)

Introduction

Type II certification covers medium-, high- and very‑high‑pressure appliances — from residential split systems and heat pumps to supermarket refrigeration racks and R‑134a chillers. This is the certification most field HVAC/R technicians rely on daily, because most everyday air‑conditioning and commercial refrigeration work is Type II.

The heart of this chapter is a table of evacuation vacuum levels that depend on the pressure class of the refrigerant, the appliance size (the 200‑pound split), and the age of your recovery equipment. Those numbers are among the most heavily tested figures on the entire certification. Learn them until they are automatic.

Learning objectives

After working through this chapter you should be able to:

• Define medium-, high- and very‑high‑pressure appliances the way 40 CFR §82.152 does (saturation pressure at 104°F) and place common refrigerants in each class.
• Recall the required evacuation levels (in inches of mercury vacuum) from §82.156 Table 1, by pressure class, by the 200‑pound size split, and by equipment age.
• Choose an appropriate leak‑detection method and pressurize a system safely.
• Apply efficient recovery techniques — liquid before vapor, managing non‑condensables, low‑loss fittings, and the 80% fill limit.

Part A — Pressure classes defined

40 CFR §82.152 sorts appliances by one measurement: the refrigerant's liquid‑phase saturation pressure at 104°F. Many study guides describe the classes by boiling point instead; the regulation does not, and the pressure class is what picks the row of the evacuation table.

Two refrigerants you meet every week are placed by the numbers rather than by name:

• R‑404A is not on the CFR's example list, but a standard R‑404A pressure‑temperature chart reads about 250 psig (roughly 265 psia) at 104°F, inside the high‑pressure band. A supermarket rack on R‑404A is a high‑pressure appliance, in the same row as R‑22 and R‑410A.
• R‑134a is often called "high‑pressure" in older material, but it sits at about 147 psia at 104°F (NIST), which makes it medium‑pressure, alongside R‑12. For comparison, R‑22 is about 222 psia (NIST).

Type II is required to service, maintain, repair, or dispose of all three of the medium-, high-, and very‑high‑pressure classes — except for small appliances (Type I) and motor‑vehicle air conditioners (which fall under Section 609) (40 CFR §82.161). If a question describes a rooftop AC unit, a heat pump, a supermarket rack or an R‑134a chiller, think Type II.

Part B — Evacuation levels: 40 CFR §82.156, Table 1

Before opening an appliance for maintenance, service, repair or disposal, you must recover the refrigerant to the level in §82.156 Table 1 (small appliances, MVACs and MVAC‑like appliances have their own rules). The level turns on three things: the pressure class, the full charge (under 200 lb, or 200 lb and more), and the date your recovery equipment was made (before, or on/after, November 15, 1993). As read on the eCFR (current September 22, 2026):

(in Hg = inches of mercury vacuum, relative to standard atmospheric pressure of 29.9 in Hg.)

Almost every exam question assumes post‑1993 equipment, so the right‑hand column is the one to own. Two rules sit beside the table:

• Not a major repair? If the work does not remove a compressor, condenser, evaporator or auxiliary heat‑exchange coil, or leave an opening of more than 4 square inches of flow area uncovered for more than 15 minutes (§82.152, "major"), and the appliance will not be evacuated to atmosphere afterward, a medium-, high- or very‑high‑pressure appliance only has to reach 0 psig before it is opened (§82.156(a)(1)(i)).
• Leaks make the level unattainable? Isolate leaking from non‑leaking parts, take the non‑leaking parts to the Table 1 level, and take the leaking part as low as you can without substantially contaminating the refrigerant — never above 0 psig (§82.156(a)(2)).

Why other guides disagree. Many study guides still print a table organized by refrigerant name — "HCFC‑22" and "other high‑pressure" — that files R‑410A, R‑404A and R‑407C under "other" at 10/15 in Hg. That was the pre‑2017 table. Since EPA's November 2016 rule took effect on January 1, 2017, the CFR table is organized by pressure class. R‑410A, R‑404A and R‑407C sit in the high‑pressure row with R‑22 (0/10); the deeper 10/15 row belongs to medium‑pressure refrigerants such as R‑12 and R‑134a. If a practice test tells you a 300‑lb R‑404A rack needs 15 in Hg, it is teaching the wrong row.

Part C — Leak detection methods

Finding leaks quickly protects the charge, the equipment, and the atmosphere. Know the common methods and their strengths:

• Electronic leak detector — highly sensitive; pinpoints small leaks by sensing refrigerant near a joint. The go‑to for finding a small leak.
• Soap‑bubble solution — brushed on a suspect fitting, it reveals larger leaks as growing bubbles.
• Fluorescent dye — added to the system, it shows leak points under ultraviolet light after the unit runs.
• Ultrasonic detector — "hears" the hiss of escaping gas.

To pressurize a system for leak testing, use dry nitrogen — sometimes with a trace of refrigerant so an electronic detector can sense it — but never oxygen or compressed air (explosion hazard with refrigerant oil). And always leak‑test and repair before recharging: charging a leaking system simply vents refrigerant and wastes money.

Part D — Recovery techniques for high‑pressure systems

Recovering a high‑pressure system efficiently means managing both liquid and vapor:

• Recover liquid before vapor on large charges. Pull liquid first through the liquid‑line port to move the bulk quickly, then switch to vapor recovery to bring the remaining gas down to the required vacuum. This greatly shortens the job.
• Purge non‑condensables. Gases such as air raise head pressure and slow recovery, so purge them and avoid drawing air into the system.
• Minimize losses. Keep hoses short and use low‑loss fittings to cut the refrigerant released when you connect and disconnect.
• Respect the 80% fill limit. Watch the recovery cylinder weight and never exceed 80% fill.
• Manage temperature. If the appliance is very cold or the ambient is low, recovery slows; warming the appliance slightly or cooling the recovery cylinder can speed the transfer.

Part E — Memorizing the evacuation table

The Part B table is the single densest set of numbers on the certification, so here is a way to hold it in your head instead of memorizing cells cold. One sentence carries it: the lower the pressure class, the deeper the vacuum. Then three steps:

1. High‑pressure (R‑22, R‑410A, R‑404A, R‑407C) is the shallow row. Under 200 lb: 0 in Hg. 200 lb and up: 10 in Hg.
2. Medium‑pressure (R‑12, R‑134a, R‑500) is one step deeper. Under 200 lb: 10 in Hg. 200 lb and up: 15 in Hg.
3. Very‑high‑pressure is 0 in Hg at any size, and low‑pressure is deepest of all (25 mm Hg absolute). With pre‑1993 equipment, nothing but a low‑pressure appliance ever needs more than 4 in Hg.

So the ladder from shallow to deep is: very‑high and small high‑pressure (0) → large high‑pressure and small medium‑pressure (10) → large medium‑pressure (15) → low‑pressure (25 mm Hg absolute). The 200‑lb line is the hinge; the pressure class picks the row.

Worked example — the large R‑404A rack. A supermarket condensing unit holds 300 lb of R‑404A and you are opening it for a compressor change with a 2019 recovery machine. To what vacuum must you evacuate? Reasoning: R‑404A reads about 250 psig (roughly 265 psia) at 104°F, inside the 170–355 psia band, so it is high‑pressure — the same row as R‑22 and R‑410A. 300 lb ≥ 200 lb and the machine is post‑1993, so Table 1 gives 10 in Hg. Guides that file R‑404A as "other high‑pressure" answer 15 in Hg; 15 is the medium‑pressure figure. Answer: 10 in Hg. (40 CFR §82.152; §82.156 Table 1.)

Part F — Leak detection and repair depth

You cannot fix what you cannot find, and Type II leans on leak‑detection judgment beyond the method list in Part C:

• Standing pressure/temperature. A system that has lost pressure since the last visit is leaking; comparing the saturation pressure to the ambient‑temperature saturation of the refrigerant tells you whether the charge is low or the system is under vacuum (drawing air).
• Match the method to the leak. The electronic detector pinpoints the small leak at a joint or flare; bubbles confirm a larger, accessible one; UV dye — circulated, run, then scanned with a UV lamp — catches the intermittent or hidden leak that only opens under running conditions; ultrasonic hears the hiss in a plant too noisy for anything else.
• Nitrogen pressure test. To confirm a repair or find a leak in an empty system, pressurize with dry nitrogen (optionally a trace of refrigerant so an electronic detector can sense it) and watch for pressure decay — never oxygen or compressed air.

Always repair before recharging. Charging a system that still leaks just meters expensive refrigerant into the atmosphere.

Part G — Retrofits and non‑condensables

• Retrofitting to a new refrigerant. As R‑22 supply tightens, systems get retrofitted to an approved substitute. The rules: the substitute must be SNAP‑approved for that end use, you usually must change the lubricant (mineral oil for CFC/HCFC vs. POE/polyol‑ester for many HFCs), you recover the old charge (never mix), and you relabel the system for the new refrigerant. Never just "top off" R‑22 with a different refrigerant — that creates an unreclaimable mixed charge.
• Non‑condensables. Air and other non‑condensable gases collect in the condenser, raise head pressure, and slow both cooling and recovery. Purge them and keep air out of the system in the first place (evacuate with a vacuum pump and hold a standing vacuum before charging a repaired system).

Worked example — retrofit compliance. A customer wants you to convert an old R‑22 rooftop unit to a lower‑cost refrigerant. List the compliance steps. Reasoning / Answer: (1) choose a refrigerant SNAP‑approved for that end use; (2) recover the R‑22 into a dedicated cylinder (do not vent, do not mix); (3) change the lubricant if the new refrigerant requires POE oil; (4) evacuate and leak‑check with nitrogen; (5) charge the new refrigerant — as a liquid if it is a zeotropic blend; (6) relabel the unit. (40 CFR Part 82, Subparts F & G.)

Part H — Charging a high‑pressure system correctly

After a repair you must put the right amount of refrigerant back — an undercharge or overcharge wrecks efficiency and can damage the compressor. Type II tests the concepts, not deep calculations:

• Weigh‑in (charge by weight). The most accurate method: recover/evacuate the system, then weigh in the exact factory charge listed on the nameplate using a scale. Best when the full charge is known and the system is empty.
• Superheat method. Superheat is how many degrees the vapor is above its saturation temperature at the suction line. On fixed‑orifice/capillary systems you charge to a target superheat — too little superheat risks liquid flooding back to the compressor; too much means the system is undercharged.
• Subcooling method. Subcooling is how many degrees the liquid is below its saturation temperature at the liquid line. On TXV (thermostatic expansion valve) systems you charge to a target subcooling; low subcooling usually means undercharge, high subcooling overcharge.
• Charge zeotropic blends as a liquid. Because R‑404A, R‑407C, and R‑410A glide and can fractionate, add them to the system as liquid (throttled so you don't slug the compressor) — never as vapor from the cylinder, which would shift the blend's composition.

Charging safety: never charge into a system you have not leak‑tested and evacuated; never use the cylinder pressure alone to judge the charge; and keep the recovery/charging cylinder on a scale.