Oklahoma HVACR Contractor Unlimited Practice Exam
Code edition notice: Oklahoma's PSI candidate bulletin (effective August 31, 2026) allows either the 2018 or the 2024 edition of the International Mechanical Code (IMC) and International Fuel Gas Code (IFGC) on this exam from September 14, 2026 through December 13, 2026. Starting December 14, 2026, only the 2024 editions are permitted.
This practice exam now cites the 2024 edition section numbers. If you are studying from the 2018 book, most section numbers are unchanged; the Chapter 1 administrative sections were renumbered in 2024. If you test on or after December 14, 2026, study from and bring the 2024 books.
Free Practice Exam
Test your knowledge with 10 questions from our pool of 20 free questions.
- 10 questions per attempt
- 30 minute time limit
- Unlimited attempts
- A new mix each time
- Instant results
Full Practice Exam
Complete exam simulation matching the real PSI test format.
- 90 questions (same as real exam)
- 240 minute time limit
- 6 topic areas covered
- 488 questions in pool
- Detailed explanations
Texts preferred · 9am–9pm Central
Oklahoma HVACR Contractor Unlimited — Practice Exam Guide
What's on the exam
Questions per topic, out of 90The Oklahoma HVACR Contractor Unlimited licensing exam consists of 90 questions delivered over 240 minutes, with a passing score of 70% (63 correct answers). The exam spans six topic areas drawn from electrical systems, natural gas, air distribution, refrigeration, heating, and safety.
Two practice options are available here:
Free practice exam: 10 questions per attempt, pulled from a limited question pool. You can retake it as many times as you like — it costs nothing and gives you a quick feel for the question style, phrasing, and difficulty level before you commit to deeper preparation.
Full practice exam (paid): 90 questions with a 240-minute time limit, mirroring the real exam exactly. Questions are drawn from a pool of 488 items, so every attempt produces a unique exam — you won't see the same set twice. All questions are based on the official topic breakdown provided by the exam authority.
Air Distribution Systems 25 items (28% of exam)
This is the heaviest topic and deserves the most study time. Expect calculation-based questions on mixed-air temperature (as shown in the sample below), duct sizing using the ACCA Ductulator (duct slide rule), and ventilation rates including air changes per hour. You must know duct system configurations — radial, extended plenum, reducing trunk, perimeter loop, and small-duct high-velocity (SDHV) — and when each is appropriate. The International Mechanical Code (2018 or 2024 edition — both are allowed) governs most of this content: duct construction materials and gauges, joining and sealing methods, and insulation requirements and vapor retarders. Registers, diffusers, grilles, and damper types are tested on function and placement, not just definition. The IMC (2018 or 2024 edition) covers outdoor air requirements and demand-controlled ventilation. Flame-spread and smoke-developed ratings for duct materials appear regularly.
Refrigeration and Air Conditioning Systems 20 items (22%)
Questions cover the full vapor-compression cycle and all four major components. Metering device questions — fixed orifice vs. TXV vs. electronic expansion valve — focus on selection criteria and operating behavior. Compressor types (reciprocating, scroll, screw, centrifugal) and their safety components are drawn from Modern Refrigeration and Air Conditioning, Chapter 18. Refrigerant classification under the EPA 608 framework is heavily tested: recovery requirements by refrigerant class, evacuation levels (see sample question below), and the distinction between low-pressure, medium-pressure, and high-pressure refrigerants. Leak detection methods, charging procedures, and proper cylinder handling all appear. Condenser and evaporator types, along with defrost methods for low-temperature applications, round out this section.
Electrical Knowledge and Controls 15 items (17%)
Every candidate must be comfortable with Ohm's Law and Watt's Law calculations in series, parallel, and series-parallel circuits. Control system questions test range and differential adjustment and the ability to calculate cut-in and cut-out set points from given values. Motor starting relays are a reliable test target: know the operating principle of current relays, potential relays, solid-state relays, and PTC (positive temperature coefficient) relays — covered in Chapter 16, Sections 16.3.5. Pressure motor controls (high-pressure, low-pressure, oil pressure) appear in Chapter 16, Section 16.3.4. NEC Article 725 governs low-voltage control circuit wiring (see sample question). Ladder diagrams and pictorial wiring diagrams are tested on reading and interpretation, not drafting.
Heating Systems 15 items (17%)
Gas-fired systems cover burner types, combination gas valves, ignition systems (standing pilot, intermittent, direct spark), and heat exchanger inspection. Oil-fired heating questions include combustion efficiency testing: CO₂ percentage, stack temperature measurement, draft testing, and smoke spot number — drawn from Modern Refrigeration and Air Conditioning, Oil-Fired Heating Systems. Hydronic heating questions address boiler components, circulator pumps, expansion tank sizing, and piping configurations (series loop, one-pipe, two-pipe, radiant). Electric resistance heating covers duct heaters, baseboard units, and sequencer operation. Load calculation questions use R-values, U-values, and the ACCA Manual N load-calculation method — know the difference between R (resistance) and U (conductance) and how to apply design temperature differences.
Natural Gas 12 items (13%)
Gas piping sizing uses three methods: longest length, branch length, and hybrid pressure — with questions drawn from the International Fuel Gas Code (2018 or 2024 edition), Table 402.4 and Appendix A. Allowable pressure drop and maximum operating pressure limits are tested directly. Combustion air sizing calculations require knowing the indoor, outdoor, and combination methods. Venting questions cover appliance categories (Category I–IV), vent types (Type B, Type BW, Type L), and termination clearances under the IFGC (2018 or 2024 edition), Sections 305.3 and 305.5. Pipe materials — steel, copper, CSST, polyethylene — and their allowable applications appear in Section 401.4 and 401.5.
Safety 3 items (3%)
Three questions, but missing one still hurts your score. Expect one question on LOTO procedures, one on SDS/GHS labeling (the nine pictogram system under HVACR Textbook, Chapter 2, Section 2.2.6), and one on fire extinguisher operation (P.A.S.S.) or refrigerant cylinder pressure safety (Chapter 2, Section 2.2.4). PPE selection and respiratory protection requirements also appear.
Sample 1 — Air Distribution Systems
A rooftop unit mixes 2,000 CFM at 65°F with 1,000 CFM at 90°F. What is the mixed air temperature?
- A. 70°F
- B. 73°F
- C. 75°F
- D. 80°F
Correct Answer: B — 73°F
Use the mass-weighted average formula: multiply each airstream's CFM by its temperature, sum the results, then divide by total CFM.
[(2,000 × 65) + (1,000 × 90)] ÷ 3,000
= [130,000 + 90,000] ÷ 3,000
= 220,000 ÷ 3,000
= 73.3°F → 73°F
The larger airstream dominates the result. Candidates who average the two temperatures (65 + 90 ÷ 2 = 77.5°F) ignore airflow weighting and select a wrong answer. Always weight by CFM.
Sample 2 — Refrigeration and Air Conditioning Systems
What evacuation level is required for low-pressure refrigerants (R-123)?
- A. 10" Hg
- B. 15" Hg
- C. 20" Hg
- D. 25 mm Hg absolute
Correct Answer: D — 25 mm Hg absolute
EPA Section 608 establishes recovery and evacuation requirements by refrigerant pressure class. Low-pressure refrigerants (such as R-123, used in centrifugal chillers) must be evacuated to 25 mm Hg absolute — a much deeper vacuum than medium- or high-pressure refrigerants require. Note that the unit is mm Hg absolute, not inches Hg vacuum. Confusing the unit or the pressure class is a common error on this question type.
Sample 3 — Electrical Knowledge and Controls
A heat pump has a reversing valve rated at 24V control voltage. What NEC Article governs control circuit wiring?
- A. 430
- B. 440
- C. 725
- D. 760
Correct Answer: C — NEC Article 725
NEC Article 430 covers motors generally; Article 440 covers hermetic refrigerant motor-compressors. Article 760 governs fire alarm circuits. Article 725 covers Class 1, Class 2, and Class 3 remote-control, signaling, and power-limited circuits — which includes the 24V low-voltage control wiring found throughout HVACR systems. Any time a question involves thermostat wire, control transformer output, or low-voltage relay coils, Article 725 is the governing reference. This is cited in Chapter 16, Section 16.4.1 of the study materials.
The passing threshold is 70%, meaning you need at least 63 of 90 questions correct on the real exam.
On your first practice attempt, treat your score as a diagnostic — a map of where you stand, not a prediction of what will happen on exam day. A score in the 50s tells you which topic areas need focused work. A score in the 60s means you're in the right range but not yet safe; keep practicing until you clear the 70% passing threshold comfortably.
The full practice exam provides a topic-by-topic breakdown after each attempt. Use it. If you scored 85% on Electrical but 55% on Air Distribution Systems (the largest topic at 25 items), your study time should reflect that imbalance — not split equally across all six areas. Run multiple attempts over several days, watching for consistent weak spots versus questions you missed once due to rushing. Consistent misses in one subtopic — say, duct sizing calculations or gas piping table lookups — tell you exactly what to review before sitting for your license.
Air Distribution Systems carries the most questions of any topic area. At 25 items, a weak performance here can knock you below passing even if you ace everything else. Two error types to watch for are unit confusion in ventilation calculations (CFM vs. ACH) and misusing the ACCA Ductulator on duct sizing problems.
Multi-step calculations across all topics — mixed-air temperature, combustion air sizing, circuit calculations — reward candidates who write out every step. Skipping steps causes unit errors and arithmetic mistakes under time pressure.
Code table lookups in Natural Gas trip up candidates who memorize concepts but haven't practiced using IFGC Table 402.4 or Appendix A sizing tables. The exam expects you to read a table accurately, not recall a number from memory.
Motor relay identification in Electrical is a point-loss trap. Current relays, potential relays, PTC relays, and solid-state relays have distinct operating principles. Mixing up when a relay opens or closes relative to motor start loses easy points.
Refrigerant pressure class errors — applying medium-pressure evacuation standards to a low-pressure refrigerant, or misidentifying a refrigerant's safety group — cost points in Refrigeration.
Time management: 240 minutes for 90 questions averages 2 minutes 40 seconds per question. Calculation-heavy sections like Air Distribution and Heating can consume disproportionate time if you're not careful.
| Detail | Value |
|---|---|
| Total questions | 90 |
| Time limit | 240 minutes |
| Passing score | 70% (63 correct) |
| Number of topic areas | 6 |
| Largest topic | Air Distribution Systems (25 items) |
| Smallest topic | Safety (3 items) |
| Practice exam — free | 10 questions per attempt |
| Practice exam — full | 90 questions, 488 question pool |