Oklahoma - HVACR CONTRACTOR UNLIMITED

Oklahoma HVACR Contractor Unlimited Exam: Complete Study Guide (2026)

Picture this: you've spent years in the trade, you know HVACR systems inside and out, and now one 90-question exam stands between you and your Oklahoma HVACR Contractor Unlimited license. That's a real opportunity — and a real pressure point. This guide breaks down exactly what's on the exam, how it's structured, and what you need to study to pass on your first attempt. Whether you're just starting to prep or fine-tuning your knowledge, you'll find actionable information here to help you get to 70% and beyond.

Oklahoma HVACR Contractor Unlimited Exam Overview

The Oklahoma HVACR Contractor Unlimited exam consists of 90 scored questions with a 240-minute time limit — that's four hours to work through problems covering everything from refrigerant handling to duct sizing to Ohm's Law.

To pass, you need to answer at least 63 of 90 questions correctly, which works out to a 70% passing score. The exam is multiple-choice, and questions range from straightforward knowledge recall to multi-step calculations that require you to apply code tables and engineering principles.

Four hours sounds like plenty of time, but calculation-heavy topics like gas piping sizing and Manual J load calculations can eat into your clock quickly. Pacing matters. Go in with a strategy: answer the questions you know first, flag the harder ones, and come back.

What Topics Are Covered?

The exam is organized into six topic areas. Here's how they break down by item count — which tells you exactly where to focus your study time.

Air Distribution Systems — 25 Items (Heaviest Weight)

This is the biggest section on the exam, covering duct system types (radial, extended plenum, reducing trunk, perimeter loop, and SDHV), duct construction materials and gauges, ACCA Manual D sizing procedures, and IMC Chapter 6 requirements for insulation and vapor retarders. You'll also need to know registers, diffusers, grilles, and damper types cold.

Refrigeration and Air Conditioning Systems — 20 Items

Expect questions on the compression refrigeration cycle, metering devices (TEVs, fixed orifice, capillary tubes), compressor types and safety components, heat exchangers and defrost methods, and refrigerant classification, environmental regulations, and EPA-compliant handling procedures.

Electrical Knowledge and Controls — 15 Items

Ohm's Law, Watt's Law, and series/parallel circuit calculations show up here, along with ladder and pictorial wiring diagrams, control system fundamentals (cut-in/cut-out settings, range and differential), and both temperature and pressure motor controls.

Heating Systems — 15 Items

Gas-fired, oil-fired, hydronic, and electric resistance heating systems are all fair game. So are combustion efficiency testing methods (CO2, stack temperature, draft, smoke tests) and heat transfer calculations using R/U/C/K values and the Manual J method.

Natural Gas — 12 Items

Gas piping materials, sizing methods (longest length, branch length, hybrid pressure), allowable pressure drop, combustion air requirements by method, and appliance venting categories (Category I–IV) are all tested here.

Safety — 3 Items

Three questions cover OSHA regulations, lockout/tagout (LOTO) procedures, fire extinguisher use (P.A.S.S.), refrigerant cylinder handling, and Safety Data Sheets (SDS) with GHS labeling.

Sample Exam Questions

Here are five representative questions to give you a feel for the depth and style of what you'll face. Think through each one — but don't scroll down looking for answers. We don't list them here on purpose. Take the free practice exam to check your thinking.

Question 1 — Heating Systems (Medium)

When calculating heating loads due to infiltration, which type of heat loss is considered?

• A) Only sensible heat loss
• B) Only latent heat loss
• C) Both sensible and latent heat loss equally
• D) Sensible heat loss plus radiant heat loss

This question tests your understanding of Manual J load calculation principles — specifically how infiltration affects the heating load calculation. It's a concept question, not a calculation, but you need to understand what infiltration does to both sensible and latent loads.

Question 2 — Natural Gas (Hard)

You are inspecting a commercial building where a contractor has installed a new gas water heater in a small utility closet. You notice there are no combustion air openings connecting the closet to adjacent spaces or the outdoors. The contractor claims the closet volume is sufficient. Using the Standard Method, what minimum volume of indoor air must be available per 1,000 Btu/h of input rating to avoid requiring outdoor combustion air openings?

• A) 25 cubic feet per 1,000 Btu/h
• B) 50 cubic feet per 1,000 Btu/h
• C) 75 cubic feet per 1,000 Btu/h
• D) 100 cubic feet per 1,000 Btu/h

This is a code application question straight out of the IFGC's combustion air requirements. You need to know the Standard Method numbers, not just the concept.

Question 3 — Refrigeration and Air Conditioning Systems (Medium)

During vapor recovery of refrigerant from a system, after the recovery machine reaches the proper vacuum level and is turned off, a technician checks the system pressure. If the pressure rises 10 psi or more after five minutes of rest, what does this most likely indicate?

• A) The recovery cylinder is overfilled and refrigerant is backflowing into the system
• B) The recovery machine's compressor valves are leaking
• C) The gauge manifold valves were not properly closed
• D) There are pockets of cold refrigerant still remaining in the system

This question tests refrigerant recovery procedures and EPA 608 requirements — the kind of diagnostic thinking a working technician uses on the job.

Question 4 — Electrical Knowledge and Controls (Medium)

You are installing an in-line ammeter to measure DC current on a control circuit. How must the ammeter be connected to obtain an accurate reading?

• A) In series with the load, with polarity disregarded since it is measuring current
• B) In parallel with the load, with leads matching polarity of the power source
• C) In series with the load, with the black lead on the negative side and the red lead on the positive side
• D) In parallel with the load, with polarity disregarded

A fundamental electrical question. If you're shaky on meter connections and polarity conventions, this topic area will bite you on the real exam.

Question 5 — Refrigeration and Air Conditioning Systems (Medium)

You are a journeyman technician called to troubleshoot a commercial refrigeration system where the compressor keeps tripping on overload during startup after the system has been off overnight in cold weather. You suspect liquid refrigerant has condensed inside the compressor crankcase. What component is designed to prevent this condition?

• A) Accumulator
• B) Discharge line thermostat
• C) Crankcase heater
• D) Oil separator

This question ties component knowledge to field diagnostics — exactly the kind of applied question the exam favors.

What Types of Questions to Expect, by Topic

Our full practice exam gives you 282 questions spread across all six exam topics. Here's what each section tests:

• Air Distribution Systems (75 practice questions): Duct system design, material selection, gauge requirements, ACCA Manual D calculations, IMC 603.2 compliance, insulation R-values, vapor retarder requirements, and identifying the right register or diffuser for a given application.
• Refrigeration and Air Conditioning Systems (64 practice questions): Cycle operation, metering device selection, compressor types and protection components, condenser and evaporator configurations, defrost control, and EPA-regulated refrigerant handling.
• Electrical Knowledge and Controls (53 practice questions): Ohm's Law and Watt's Law calculations, series/parallel/series-parallel circuits, reading and interpreting ladder diagrams, control system settings, sensing bulb and thermistor applications, and high/low pressure control operation.
• Heating Systems (45 practice questions): Component identification and operation for gas, oil, hydronic, and electric heating systems; combustion analysis testing; hydronic piping configurations; and Manual J load calculations using R/U/C/K values.
• Natural Gas (36 practice questions): Pipe material selection, sizing table application across multiple methods, pressure drop limits, indoor/outdoor combustion air calculations, and venting category identification.
• Safety (9 practice questions): OSHA employer reporting rules, LOTO procedures, fire extinguisher types and the P.A.S.S. technique, refrigerant cylinder safety, and SDS/GHS label interpretation.

Study Materials You'll Need

The Oklahoma exam draws from established codes and technical references. These four resources cover the exam content directly.

Modern Refrigeration and Air Conditioning (20th Edition) — This is the standard textbook for refrigeration and air conditioning systems. It covers the compression cycle, metering devices, compressors, refrigerants, and electrical controls in thorough detail. If you're studying the refrigeration and electrical sections, start here.

Mathematics for Plumbers and Pipefitters (8th Edition) — Don't underestimate the math on this exam. Gas piping sizing, combustion air calculations, and load calculations all require applied arithmetic. This book builds the calculation skills you'll use across multiple topic areas.

2018 International Mechanical Code (IMC) — The Air Distribution Systems section of the exam is grounded in the IMC, particularly Chapter 6 (duct construction and insulation) and the duct sizing tables. You need to be comfortable pulling information from these tables under time pressure.

2018 International Fuel Gas Code (IFGC) — The Natural Gas section is built on the IFGC. Combustion air requirements, venting categories, pressure limits, and piping materials all come from this code. Study the sizing tables and combustion air sections especially hard.

Study Tips for the Oklahoma HVACR Contractor Unlimited Exam

Prioritize by weight. Air Distribution Systems (25 items) and Refrigeration and Air Conditioning Systems (20 items) together account for half the exam. That's where your study time should go first.

Work the code tables, not just the concepts. The IMC and IFGC questions often require you to apply sizing tables, not just recall rules. Practice pulling numbers from those tables quickly.

Do the math by hand. Gas piping sizing, Ohm's Law calculations, and load calculations will appear on the exam. Use practice problems with actual numbers — don't just read through solutions.

Know your refrigerant handling rules cold. EPA 608 regulations, recovery requirements, and environmental classifications appear across multiple questions in the refrigeration section.

Use the full four hours if you need to. Don't rush. Flag calculation questions that take more than two minutes and come back to them after you've answered everything you know.

Start with the free exam, then go deeper. Take the free practice exam to see where you stand. Then use the full paid practice exam — which mirrors the real exam's 90 questions, time limit, and topic breakdown — to get a detailed score breakdown by section and identify exactly where to focus.

Frequently Asked Questions

How many questions are on the Oklahoma HVACR Contractor Unlimited exam?
The exam has 90 scored questions. You have 240 minutes to complete it.

What is the passing score?
You need to answer 63 out of 90 questions correctly — a 70% passing score.

Which topic has the most questions?
Air Distribution Systems is the heaviest section with 25 exam items, followed by Refrigeration and Air Conditioning Systems with 20 items.

What codes does the exam reference?
The exam draws primarily from the 2018 International Mechanical Code (IMC) and the 2018 International Fuel Gas Code (IFGC), along with established HVACR technical standards.

Can I use the practice exam to prepare if I've never taken an HVACR licensing exam before?
Absolutely. Start with the free exam (10 questions, no account required) to get a feel for the question style. Then use the full practice exam for realistic timed sessions with topic-by-topic score breakdowns. Both are useful no matter where you are in your prep.

Ready to Start Preparing?

The Oklahoma HVACR Contractor Unlimited license opens doors — commercial projects, larger contracts, and the credibility that comes with holding an unlimited contractor's license. The exam is thorough, but it's designed around things you work with every day. With the right references, focused study on the highest-weight topics, and realistic practice under timed conditions, 70% is very achievable.

Start by taking the free practice exam right now — no signup, no payment, just 10 real questions to show you where you stand. Then pick up your code books, work through the calculations, and build from there. You've got this.