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Oklahoma Refrigeration Contractor Licensing Exam — Practice Test Guide

What This Practice Exam Covers

The Oklahoma Refrigeration Contractor licensing exam consists of 80 questions with a 210-minute time limit. You need a score of 70% (56 correct) to pass. The exam spans six topic areas drawn from electrical theory, refrigerants, piping, equipment, system operations, and safety.

This practice site offers two options:

• Free practice exam: 10 questions per attempt, pulled from a limited question pool. You can retake it as many times as you like to get comfortable with the question format and style — a solid first step before committing to full prep.
• Full practice exam (paid): Mirrors the real exam exactly — 80 questions, 210-minute time limit. Questions are drawn from a pool of 363+ items, so every attempt is a different exam. No two sittings produce the same question set, which means repeated attempts build genuine mastery rather than answer memorization.

Both options are built around the exact topic blueprint the official test provider uses.

What You'll Be Tested On

Electrical Knowledge and Controls — 20 items

This is the largest topic area and deserves the most study time. Questions range from foundational math (Ohm's Law: V = IR; Watt's Law: P = IE) to multi-step circuit analysis across series, parallel, and series-parallel configurations. You must be able to calculate total resistance, current draw, and voltage drops — not just recognize the formulas.

Expect questions on power factor and apparent vs. true power: distinguishing kVA from kW, and knowing how capacitors improve power factor in inductive motor circuits (Modern Refrigeration and Air Conditioning, Section 13.1.3). Single-phase and three-phase supply systems are both tested, including how reversing two leads on a three-phase motor reverses rotation (Modern Refrigeration and Air Conditioning, Section 15.2.2).

Motor types are heavily represented: split-phase, CSIR, CSCR, PSC, and shaded-pole motors each have distinct starting characteristics. You need to know which motors use run capacitors, which use start capacitors, and which use neither. Motor starting and running relays — current relays, potential relays, solid-state relays, and PTC relays — are tested on how they function, how to check them, and where they are wired (Modern Refrigeration and Air Conditioning, Section 16.3.5).

Low-voltage control circuits, transformer operation, ladder diagrams, and fuse selection also appear (Modern Refrigeration and Air Conditioning, Section 16.4.1; Section 12.7).

Refrigerants — 20 items

This section tests both regulatory knowledge and hands-on procedure. You must know the refrigerant numbering and classification system — what makes a refrigerant a CFC, HCFC, HFC, HFO, hydrocarbon, or inorganic compound — and the environmental significance of each class in terms of ODP (ozone depletion potential) and GWP (global warming potential).

EPA Section 608 compliance is embedded throughout: recovery, recycling, and reclaiming are distinct processes and the exam treats them that way. Know what equipment is required for each, and understand Type III (low-pressure system) recovery techniques specifically (EPA Section 608, Type III Recovery Techniques).

System evacuation is tested numerically. The standard deep vacuum target is 500 microns, and you must know both deep vacuum and triple evacuation procedures, including when each is appropriate and what a micron gauge is measuring (Modern Refrigeration and Air Conditioning, Page 255, Section 11.4.2).

Cylinder color codes, DOT transport regulations, and proper cylinder handling (never refill disposable cylinders, never exceed 80% fill capacity for recovery cylinders) are also tested. Leak detection methods — electronic detectors, UV dye, soap bubbles — and refrigerant retrofit procedures including R-22 to R-410A retrofit considerations round out this section (Modern Refrigeration and Air Conditioning, Pages 265–266, Section 11.5.3).

Piping — 5 items

Fewer questions, but they require precision. Know the difference between ACR tubing Types K and L, soft-drawn versus hard-drawn copper, and when each is appropriate. Flaring procedures — single versus double flare, correct flare angle, and torque — are tested procedurally, not just conceptually.

Soldering versus brazing distinctions matter: brazing uses filler metals above 840°F and requires purging with nitrogen to prevent oxide scale formation inside the tubing. Swaged connections and joining dissimilar metals also appear. Non-refrigerant piping materials (ABS, PVC, CPVC, steel) are fair game — know which plastic type is rated for which temperature and pressure range.

Refrigeration Equipment and Components — 20 items

The second largest section. Compressor types — reciprocating, rotary, scroll, screw, and centrifugal — are tested on construction details, applications, and failure modes. Open-drive, hermetic, and semi-hermetic configurations each have specific maintenance and serviceability implications (Modern Refrigeration and Air Conditioning, Chapter 18, Sections 18.1.1 and 18.1.2).

Metering devices require you to distinguish capillary tubes, metering orifices, TXVs, AXVs, EEVs, and float controls by operating principle. For TXVs, know externally versus internally equalized designs and what "hunting" means (Modern Refrigeration and Air Conditioning, Chapter 20, Section 20.4.1).

Condenser and evaporator types, defrost methods and controls, filter-drier placement, sight glass interpretation, solenoid valves, check valves, and service valve positions are all tested. Safety and protection devices — crankcase pressure regulators, discharge pressure switches, oil separators, and accumulators — are a consistent source of questions (Modern Refrigeration and Air Conditioning, Chapter 19, Sections 19.2 and 19.3.1).

Refrigeration Systems Operations — 10 items

Expect pressure-enthalpy diagram questions where you must interpret a plotted cycle and identify which condition (overcharge, undercharge, noncondensables, moisture contamination) is indicated by abnormal pressure or enthalpy values. You need to understand all four phases of the refrigeration cycle well enough to diagnose problems from symptom descriptions.

Heat load calculation and component sizing for commercial systems is tested, along with multiple-evaporator system configurations, compound (multistage) systems, and secondary loop arrangements (Modern Refrigeration and Air Conditioning, Chapter 49, Section 49.4.1).

Safety — 5 items

Questions are code-specific. Know lockout/tagout (LOTO) procedure steps and when each applies. PPE selection — eye protection, hearing protection, and respiratory protection — is tested against specific regulatory thresholds (29 CFR 1926, §1926.95(d)(1); 29 CFR 1926, §1926.100(a) and (b)(1)). Fire extinguisher requirements (29 CFR 1926, §1926.150(c)(1)(i)), flammable liquid storage (29 CFR 1926, §1926.152(b)(1)), and compressed gas cylinder handling (29 CFR 1926, §1926.350(a)(10)) are all represented. Read SDS requirements carefully — questions test specific sections and what information must appear.

Worked Sample Questions

Question 1 — Electrical Knowledge and Controls

Low voltage HVAC control wiring (24V thermostat) is protected by:

• A. 10A fuse
• B. 15A breaker
• C. Manufacturer's internal fuse
• D. Protected at panel

Correct Answer: C

Class 2 low-voltage circuits (like a 24V thermostat circuit) are limited inherently by the transformer's output capacity or protected by a fuse built into the equipment by the manufacturer — not by a panel breaker or a separately installed fuse. The exam tests this because many candidates assume the panel handles all overcurrent protection. The distinction matters: the internal fuse protects the control circuit, not the supply side. Source: Modern Refrigeration and Air Conditioning, Section 16.4.1 — Fuses.

Question 2 — Refrigerants

When evacuating an HVAC system, target vacuum should reach:

• A. 250 microns
• B. 500 microns
• C. 1,000 microns
• D. 2,000 microns

Correct Answer: B

The industry-standard deep vacuum target is 500 microns. Above this level, residual moisture and noncondensables remain in the system and will cause contamination, acid formation, and compressor damage. The micron gauge — not a standard manifold gauge — must be used to verify this level. Many candidates incorrectly select 250 microns (too aggressive for most field conditions) or 1,000 microns (not tight enough). Source: Modern Refrigeration and Air Conditioning, Page 255 (Section 11.4.2, Deep Vacuum Evacuation Procedure Step 7).

Question 3 — Refrigeration Equipment and Components

Why is the exhaust valve on a reciprocating compressor more susceptible to problems than the intake valve?

• A. The exhaust valve uses a poppet design while the intake valve uses a simpler reed design
• B. The exhaust valve operates at higher temperatures and pressures, promoting carbon deposits from hydrocarbon oil on the valve and seat
• C. The exhaust valve is located on the cylinder side of the valve plate where it receives less lubrication
• D. The exhaust valve opens more frequently per revolution than the intake valve

Correct Answer: B

The exhaust valve must seal against high discharge pressure and operates in a high-temperature environment. These conditions cause heavy hydrocarbon oil molecules to break down and deposit as carbon on the valve face and seat — a failure mechanism the intake valve does not face because it is continuously bathed in cool, incoming refrigerant vapor. Carbon buildup causes the valve to leak, reducing compression efficiency and damaging the compressor. Source: Modern Refrigeration and Air Conditioning, Chapter 18, Section 18.2.1 — Valves and Valve Plates*.

How to Read Your Score

The passing threshold is 70%, meaning you need 56 correct out of 80 on the real exam.

Treat your first practice attempt as a diagnostic, not a verdict. A first score below 70% tells you which topic areas need work — that is exactly the information you need at the start of preparation. A score in the low 70s on a first full practice attempt should be taken as a warning, not a green light; the real exam will include questions drawn from the full depth of each topic, and scoring near the floor of passing on practice usually means gaps remain.

Use the topic-by-topic breakdown after each attempt. If you score well on Safety (5 items) but poorly on Electrical Knowledge and Controls (20 items), your study time allocation should reflect that imbalance. The Refrigerants and Equipment sections (20 items each) are the highest-leverage areas for recovering points.

Repeated attempts on the full practice exam are effective precisely because the 363+ question pool means you encounter new questions each time — you're building broad knowledge, not memorizing a fixed answer set. Start with the free exam to calibrate your baseline, then use the full exam for structured preparation.

Where Candidates Lose Points

Electrical calculations are the most common point-loss area. Candidates mix up series and parallel resistance rules, or apply Ohm's Law correctly but use the wrong unit (amps vs. milliamps, volts vs. millivolts). Power factor questions trip up people who haven't practiced converting between apparent power (kVA) and true power (kW).

Refrigerant procedures cost points when candidates conflate recovery, recycling, and reclaiming — three legally distinct processes under EPA Section 608. Evacuation questions are frequently missed because candidates don't know the 500-micron standard or don't recognize that a standard manifold gauge cannot verify deep vacuum.

Equipment and compressor questions require knowing specific construction details — for example, why carbon deposits form on exhaust valves but not intake valves, or the exact function of a crankcase pressure regulator versus a discharge pressure switch. Generic answers that sound plausible are the designed wrong-answer traps here.

Safety questions are code-section specific. Candidates who know the concept but not the regulation (e.g., knowing PPE is required but not which specific 29 CFR 1926 section governs it) lose points to answer choices that cite plausible-sounding but incorrect sections.

Finally, time management: 210 minutes for 80 questions averages 2.5 minutes per question. Multi-step electrical and heat load calculations can easily consume 5+ minutes each if you're not careful — bank time on straightforward recall questions so you have room for calculation problems.

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