Type III — low-pressure appliances

25% of the EPA 608 · blueprint 40 CFR part 82 subpart F, appendix D, section d (test content)

Short answer

Type III certifies work on low-pressure appliances — those using a refrigerant with a liquid-phase saturation pressure below 45 psia at 104 °F, such as R-11, R-123 and R-245fa. Low-pressure centrifugal chillers run under a vacuum, which inverts most of what Type II teaches: leaks draw air and moisture in rather than pushing refrigerant out, recovery is to 25 mm Hg absolute, and pressurising for a leak test is done with controlled heat first, with nitrogen only as the fallback.

Why it matters on this exam

Type III is the section where transferring Type II habits actively costs marks. A low-pressure machine operates below atmospheric pressure, so a leak lets air and moisture in. That single fact explains the purge unit, the freeze risk, the pressurisation rules and most of the 25 items.

Key concepts

What low-pressure means. Section 82.152: a refrigerant with a liquid-phase saturation pressure below 45 psia at 104 °F. R-11, R-123, R-113 and R-245fa are the named examples.
Recovery level. Table 1 gives a single figure for low-pressure appliances regardless of equipment age: 25 mm Hg absolute. This is the one row in Table 1 not expressed in inches of mercury vacuum, and it is worth memorising in that form.
Recover vapour as well as liquid. Pulling the liquid out is not the end of the job on a low-pressure machine.
Pressurising for a leak test. Order of preference: the hot water method or a built-in system heating and pressurisation device, then nitrogen. Section 82.156(a)(1)(ii) makes the logic explicit for non-major repairs — where the refrigerant boils at or below 85 °F at atmospheric pressure you must not use a method like nitrogen that requires purging afterwards; where it boils above 85 °F you use heat to raise the internal pressure as far as it will go, and may then use nitrogen to bring it up to atmospheric. Never exceed the maximum leak-test pressure for the chiller.
The purge unit removes non-condensables that leak in. Excessive purging is the classic sign of a leak into a low-pressure system.
Freeze prevention. Circulate or remove the water from the chiller during evacuation, or the water in the tubes will freeze as the refrigerant boils off and the tubes will split.
Recharging: vapour before liquid, for the same reason. Introduce vapour first to raise the temperature in the tubes before liquid arrives. Charge centrifugals through the evaporator charging valve.
Heat oil to 130 °F before removing it, to drive off dissolved refrigerant and minimise release.
High-pressure cut-out. Recovery devices used with low-pressure appliances have a cut-out level you need to know.
ASHRAE Standard 15 requires an oxygen deprivation sensor in the equipment room with all refrigerants, and specifically a refrigerant sensor for R-123.

Common mistakes

Reaching for nitrogen first. On a low-pressure system, controlled heat is the preferred pressurisation method and nitrogen is the fallback, because nitrogen has to be purged afterwards.
Evacuating a chiller without dealing with the water. The refrigerant boiling off absorbs heat from the water in the tubes; if it is standing still, it freezes.

Worked example

An R-11 centrifugal chiller is purging far more often than it used to. On a machine running under a vacuum, that points to air and moisture being drawn in through a leak rather than refrigerant escaping — which is why the same symptom means something different here than on a high-pressure system. Before opening it for a non-major repair, note that R-11 boils at about 75 °F at atmospheric pressure, at or below the 85 °F line, so you must not use a method such as nitrogen that requires subsequent purging; you pressurise with controlled heat (hot water or a built-in heating device) to no higher than 0 psig. If you were recovering for service instead, the target is 25 mm Hg absolute, with the chiller water circulating throughout.

Original practice questions

Type III — low-pressure appliancesDifficulty 3/5

What evacuation level does Table 1 require for a low-pressure appliance?

ATwenty-five inches of mercury vacuum, whatever the age of the recovery equipment
BTen inches of mercury vacuum, if the recovery equipment was made after 1993
CFifteen inches of mercury vacuum, if the charge is two hundred pounds or more
DTwenty-five millimetres of mercury absolute, whatever the age of the equipment

Show answer and rationale

Correct: D. The low-pressure row is the only one in Table 1 expressed as an absolute pressure rather than a vacuum, and the only one that does not change with the age of the recovery equipment.

A — The figure is twenty-five millimetres of mercury absolute, not twenty-five inches of vacuum.
B — Ten inches applies to high-pressure appliances of two hundred pounds or more.
C — Fifteen inches applies to medium-pressure appliances of two hundred pounds or more.

Type III — low-pressure appliancesDifficulty 2/5

A low-pressure centrifugal chiller has begun purging far more frequently than before. What does this most likely indicate?

AAir and moisture are being drawn into the system through a leak below atmospheric
BRefrigerant is escaping from the system through a leak above atmospheric pressure
CThe chiller is overcharged and the purge unit is removing the excess refrigerant
DThe purge unit has failed and is cycling without removing any gas from the system

Show answer and rationale

Correct: A. A low-pressure machine runs below atmospheric pressure, so a leak lets air in rather than letting refrigerant out. The purge unit then works harder removing the non-condensables, which is the signature symptom.

B — The system sits below atmospheric pressure, so the pressure gradient drives air inward.
C — Purge units remove non-condensable gases, not surplus refrigerant from an overcharge.
D — A failed purge unit would show as rising non-condensables, not as increased purging.

Type III — low-pressure appliancesDifficulty 4/5

Why must water be circulated through or removed from a chiller while its refrigerant is being evacuated?

AWater circulation is required to keep the purge unit operating during the evacuation
BBoiling refrigerant absorbs heat and standing water in the tubes will freeze and split them
CCirculating water raises the system pressure and shortens the time recovery takes
DMoving water prevents sediment settling and blocking the evaporator tube bundle

Show answer and rationale

Correct: B. Evaporating refrigerant draws its latent heat from whatever is nearest, which is the water in the tubes. Ice expands, and a split tube bundle is an expensive and entirely avoidable failure.

C — Circulation does not meaningfully raise system pressure or accelerate the recovery.
D — Sediment is a maintenance concern generally, not the reason for circulating during evacuation.
A — Purge units operate independently of whether the chiller water is moving.

All 5 Type III — low-pressure appliances questions →

Tools for this topic

EPA 608 certification type finder — Type I, II, III or Universal is decided by the equipment you work on and what you do to it, not by your job title. This walks the rule at 40 CFR 82.161(a)(1) and gives you the type, with the citation.

6 flashcards for Type III — low-pressure appliances

Practice this topic

Blueprint-mapped questions with full rationales for every choice.

Start practice

Primary references

40 CFR Part 82 Subpart F — Recycling and Emissions Reduction — Office of the Federal Register (eCFR) · government · retrieved 2026-09-22, verified 2026-09-22
Section 608 Test Topics — United States Environmental Protection Agency · primary · retrieved 2026-09-22, verified 2026-09-22

Last reviewed: 2026-10-18Next review by: 2026-12-17Reviewed by: Openverse editorial team, Authoring and fact verificationHow we verify facts