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Oklahoma HVACR Contractor, Limited — Practice Exam Prep Guide

What This Practice Exam Covers

The Oklahoma HVACR Contractor, Limited licensing exam contains 80 questions answered within 210 minutes, with a 70% passing score (56 correct answers) required.

Two practice options are available:

• Free practice exam: 10 questions per attempt drawn from a limited pool. You can retake it as many times as you like — it costs nothing and gives you a real feel for the question style and difficulty before you commit further time or money.
• Full practice exam (paid): Mirrors the real exam exactly — 80 questions, 210-minute timer. Questions are drawn from a pool of 520+ items, so every attempt presents a unique exam with no duplicate sets. Topics match the official content outline provided by the licensing authority.

Start with the free exam to gauge your baseline, then use the full practice exam for serious, timed preparation as your test date approaches.

What You'll Be Tested On

Electrical Knowledge and Controls — 15 items

This is one of the two heaviest sections. Expect Ohm's law and Watt's law calculations where you must solve for voltage, current, resistance, or power given two knowns — no formula sheet provided. You need to read and interpret both pictorial and ladder diagrams, identifying component symbols and tracing current paths. Motor questions cover split-phase, capacitor-start induction-run, capacitor-start capacitor-run, permanent split capacitor, and shaded-pole motors — know which uses a start capacitor, which uses a run capacitor, and why. Motor starting relays (current, potential, solid-state, and PTC types) appear regularly; know which relay is normally open vs. normally closed at rest. Pressure and temperature motor controls require you to understand cut-in, cut-out, range, and differential — not just define the terms but apply them to a scenario. Motor protection questions cover fuse sizing, circuit breaker selection, and bimetal vs. thermistor overload operation. (References: Modern Refrigeration and Air Conditioning, Chapter 13, Sections 13.1 and 13.2.1; Chapter 15, Sections 15.2.1 and 15.2.2; Chapter 16, Sections 16.1.1, 16.1.2, 16.3.4, 16.3.5, 16.4.1, and 16.4.3)

Natural Gas — 12 items

Pipe material rules (steel, copper, CSST, PE) and where each is and is not permitted. Gas piping sizing uses capacity tables — you must know the difference between the longest-length and branch-length methods and be able to read Table A.3.4 correctly. Pressure testing and leak checks are tested procedurally: know test pressures, required hold times, and acceptable test media. Combustion air questions use the indoor, outdoor, and combination methods from IFGC Section 304 — you may need to calculate required opening sizes. Venting questions require matching appliance category (I through IV) to the correct vent type, and understanding why draft-hood appliances and fan-assisted appliances size differently. (References: 2018 IFGC, Sections 304.5.1, 304.5.2, 304.6.2, 304.10, 304.11, 402.4.2, 402.4.3, Table 402.4, 406.4, 406.7.1.3, 503.3.4, 503.5.7.1, 503.7.2, 503.7.5, 503.7.7, 503.12.2.1, 503.12.5, 503.12.7)

Air Distribution Systems — 15 items

Another 15-item section. Know the five duct system configurations: radial, extended plenum, reducing trunk, perimeter loop, and small-duct high-velocity (SDHV) — their applications and limitations. ACCA Manual D duct sizing is tested; understand the equivalent length concept and total effective length. Registers, diffusers, and grilles questions ask about throw, spread, and placement relative to supply and return locations. Damper types — butterfly, multiple-blade, split, fire, and smoke — require you to know how each operates and where it is installed. Duct insulation and sealing questions reference IMC requirements for vapor retarders and duct sealing classes. Airflow measurement covers flow hoods, manometers, pitot tubes, blower door testing, and duct blaster testing — know what each tool measures and how results are interpreted. (References: International Mechanical Code 2021, Sections 601.5, 603.2, 603.3, 603.4.2, 603.5, 603.5.1, 603.6.1.1, 603.6.3, 603.7, 603.8, 603.8.1, 603.8.2, 603.8.3, 603.9, 604.2, 604.7, 604.8, 604.13, 605.1)

Refrigeration and Air Conditioning Systems — 20 items

The largest section. You need to trace refrigerant through every stage of the compression refrigeration cycle and explain what each component does to pressure, temperature, and state. Refrigerant classification covers ASHRAE safety groups (A1, A2, B1, B2, etc.) and environmental regulations under EPA Section 608. Know recovery, recycling, and reclaiming as distinct processes — and the specific rules for Type III (low-pressure) recovery techniques. Metering device questions compare capillary tubes, TXVs, AXVs, EEVs, and fixed-orifice types — know which responds to superheat and which does not. Compressor types (reciprocating, scroll, rotary, screw, centrifugal) and their protection devices (high-pressure cutout, motor overload, crankcase heater) are all fair game. Gauge manifold use, cylinder color coding, and leak detection methods are tested practically. (References: Modern Refrigeration and Air Conditioning, Chapter 12, Sections 12.1.3, 12.4.2, 12.4.4, 12.4.5; Chapter 18 – Compressors; EPA Section 608, Type III Recovery Techniques)

Heating Systems — 15 items

Gas-fired heating questions cover burner types, ignition systems (standing pilot, intermittent, direct spark, hot surface), and gas valve/combustion control sequencing. Oil-fired systems require knowledge of burner components (nozzle, electrodes, pump, transformer), fuel delivery, and combustion efficiency testing (stack temperature, CO₂ percentage, smoke number). Hydronic systems test boilers, circulating pumps, expansion tanks, and terminal units; know series loop, one-pipe, two-pipe, zoned, and radiant system configurations. Heat pump questions focus on reversing valve operation, metering device selection for heating vs. cooling mode, and defrost control logic. Electric resistance heating covers duct heaters, baseboard units, and radiant panels. (References: Modern Refrigeration and Air Conditioning, pages covering heat pump operation, oil-fired systems, and hydronic components)

Safety — 3 items

Three questions, but three easy points if you know the material. Expect lockout/tagout (LOTO) procedure steps, P.A.S.S. fire extinguisher technique (Pull, Aim, Squeeze, Sweep), refrigerant cylinder handling (never drop, store upright, keep from heat sources), PPE selection, and GHS/HCS labeling including the nine pictogram meanings and the six SDS section categories most relevant to field work. (References: HVACR Textbook, Chapter 2, Sections 2.2.2, 2.2.4, 2.2.6)

Worked Sample Questions

Sample 1 — Refrigeration and Air Conditioning Systems

Question: Compressor amps high, liquid line warm, outdoor fan off. What mode?

• A. Heating
• B. Cooling
• C. Defrost
• D. Emergency heat

Correct Answer: C — Defrost

During a defrost cycle, the outdoor fan is intentionally de-energized so that heat from the refrigerant can melt frost on the outdoor coil rather than being dispersed into the ambient air. The reversing valve shifts to move hot refrigerant gas to the outdoor coil, which is why the liquid line feels warm to the touch. Compressor amperage rises because the system is working against different load conditions. None of the other options explain the outdoor fan being off while the compressor runs — heating mode and cooling mode both require the outdoor fan, and emergency heat bypasses the refrigerant circuit entirely.

Sample 2 — Electrical Knowledge and Controls

Question: Using nameplate MOCP 50A, what is maximum allowed breaker?

• A. 40A
• B. 45A
• C. 50A
• D. 55A

Correct Answer: C — 50A

The Maximum Overcurrent Protection (MOCP) value printed on the equipment nameplate is a hard ceiling set by the manufacturer under NEC 440.22. You may not install a breaker larger than what the nameplate specifies. A 55A breaker exceeds the 50A MOCP and is not permitted. Going smaller (40A or 45A) would be conservative but may cause nuisance tripping on motor startup — and the question asks for the maximum allowed, which is exactly 50A. Always match or stay below MOCP; never exceed it.

Sample 3 — Air Distribution Systems

Question: The amount of return air taken from any room or space is limited to what maximum value?

• A. The flow rate of exhaust air removed from that space
• B. 125 percent of the supply air delivered to that space
• C. 80 percent of the supply air delivered to that space
• D. The flow rate of supply air delivered to that space

Correct Answer: D — The flow rate of supply air delivered to that space

Per International Mechanical Code 2021, Section 601.5, the quantity of return air extracted from any room or space shall not exceed the rate of supply air delivered to that space. This prevents rooms from being placed under negative pressure relative to adjacent areas, which could draw pollutants or combustion gases into occupied spaces. Options B and C (percentages) are fabricated thresholds that do not appear in the code. Option A confuses exhaust with return — exhaust air is permanently expelled, while return air recirculates.

How to Read Your Score

The passing threshold is 70% — 56 correct answers out of 80 on the real exam. On the full practice exam, that same target applies.

Your first practice attempt is a diagnostic, not a judgment. Most candidates discover gaps they did not know they had — particularly in gas piping sizing calculations, refrigerant regulation specifics, or motor relay identification. A score in the 60s on your first attempt is not discouraging; it is useful information.

Use the topic breakdown your results provide. If your Refrigeration and Air Conditioning score is low, that costs more points (20 items) than a similar gap in Safety (3 items) — prioritize accordingly. If you are passing overall but failing one section, targeted review of that topic's subtopics is more efficient than re-reading everything.

Scoring 75–80% consistently across multiple practice attempts with different question sets is a more reliable readiness signal than one high score. Because the full practice exam draws from 520+ questions, each retake tests genuinely different content — treat each attempt as its own exam, not a memorization exercise.

Where Candidates Lose Points

Calculation errors under time pressure. Ohm's law and Watt's law questions are straightforward but require careful unit handling. Mixing up watts and volt-amps, or forgetting to account for three-phase power factor, costs points that should be automatic.

Wrong table in gas piping sizing. The longest-length and branch-length methods use different table entries. Candidates who apply the correct procedure to the wrong column — or confuse Table A.3.4 with a different sizing table — arrive at a plausible but wrong pipe size.

Confusing return air with exhaust air. This distinction appears in Air Distribution questions and has a direct code answer (IMC 2021, Section 601.5). Candidates who treat the two as interchangeable miss the question.

Misidentifying motor starting relay behavior. Potential relays are normally closed; current relays are normally open. Getting these backward leads to wrong answers on diagnostic scenario questions.

Defrost mode symptoms. As shown in Sample 1 above, candidates unfamiliar with defrost logic often select "heating mode" when they see warm refrigerant lines — missing the outdoor fan detail that changes the answer.

Running out of time. With 80 questions and 210 minutes, you average 2.6 minutes per question. Lengthy piping sizing or combustion air calculation questions can consume 4–5 minutes if you are not fluent with the procedure, leaving you rushing through later sections.

Exam Quick Facts