- What the OH-REF Trade Exam Actually Tests
- Exam Format, Timing, and Scoring
- Domain-by-Domain Breakdown
- Eligibility and Application Mechanics
- Fees, Retesting, and What Everything Costs
- Approved References and Open-Book Rules
- A Domain-Weighted Study Timeline
- Don't Forget the Business and Law Exam
- After You Pass: Licensing and Renewal
- Frequently Asked Questions
- The OH-REF trade exam has 60 scored questions (plus 10 unscored pretest items) and a 70% passing score.
- General Knowledge & Requirements carries the most weight at 18 of 60 scored questions.
- PSI charges $69 per exam attempt, and the trade exam and Business and Law exam are billed separately.
- Testing is open-book, but only pre-highlighted, pre-tabbed references are allowed - no handwritten notes.
What the OH-REF Trade Exam Actually Tests
The Ohio Refrigeration Contractor License Exam (OH-REF) is administered through PSI on behalf of the Ohio Construction Industry Licensing Board (OCILB), a division of the Ohio Department of Commerce's Division of Industrial Compliance. This is a trade-specific credential, and it's important to be precise about what "refrigeration" means in this context: OCILB refrigeration licensing governs food and product preservation systems, not comfort-cooling HVAC work. If your background is mostly residential air conditioning, you'll need to shift your study focus toward commercial refrigeration equipment, walk-in coolers, freezers, and preservation-related controls.
Because the acronym "OH-REF" is used loosely online, make sure any resource you study from is specifically built around the Ohio trade exam and its companion Business and Law exam - not a similarly named credential from another state or industry. For a full walkthrough of what the credential covers and who it's for, see What Is OH-REF? and OH-REF Meaning.
Exam Format, Timing, and Scoring
The OH-REF trade examination consists of 60 scored questions plus 10 unscored pretest questions, for 70 questions administered in total, within a 3-hour time limit. You need a 70% passing score on the scored portion to pass. The unscored pretest questions are mixed in without identification, so every question should be treated as if it counts.
The test is computer-based and delivered as an open-book exam, which changes your prep strategy significantly compared to closed-book licensing tests. Instead of memorizing every code table cold, you're being tested on your ability to locate, interpret, and apply information quickly under time pressure. Only PSI's onscreen calculator is permitted - no personal calculators, phones, or other devices.
Key Takeaway
Because this is open-book, your prep time is best spent learning where information lives in your references and practicing retrieval speed, not rote memorization. Tab and index your code book and textbook well before test day.
Domain-by-Domain Breakdown
PSI's official bulletin breaks the 60 scored questions into five domains. Understanding this weighting is the single most useful thing you can do to prioritize study time - a topic worth 18 questions deserves far more attention than one worth 6. For an in-depth walkthrough of each domain's content and sample question styles, see OH-REF Exam Domains 2026: Complete Guide to All 5 Content Areas.
| Domain | Scored Questions | Share of Exam |
|---|---|---|
| 1. General Knowledge & Requirements | 18 | Largest domain |
| 2. Refrigeration Piping | 12 | Second largest |
| 3. Refrigerants | 6 | Smallest, tied |
| 4. Refrigeration Systems & Controls | 15 | Second largest |
| 5. Testing & Inspection | 9 | Mid-weight |
Domain 1: General Knowledge & Requirements
At 18 of 60 scored questions, this is the single highest-weighted domain and covers the regulatory and administrative knowledge that underpins contractor licensing in Ohio, including code references drawn from the 2024 Ohio Mechanical Code.
- Ohio Mechanical Code provisions relevant to refrigeration installations
- Contractor obligations and general licensing framework
- Safety and jobsite requirement fundamentals
Domain 2: Refrigeration Piping
With 12 scored questions, piping design and installation practices form a major chunk of the exam. Expect questions rooted in sizing, layout, and material selection as covered in Modern Refrigeration and Air Conditioning, 22nd edition.
- Piping sizing and routing principles
- Material compatibility for refrigeration lines
- Installation best practices tied to code
Domain 3: Refrigerants
The smallest domain at 6 scored questions, but not one to skip - refrigerant handling, properties, and safety knowledge are foundational to the trade.
- Refrigerant properties and classifications
- Handling and safety considerations
- Application to preservation-focused equipment
Domain 4: Refrigeration Systems & Controls
At 15 scored questions, this is the second-largest domain and focuses on the operating logic of refrigeration systems - compressors, controls, and system components used in food and product preservation.
- System components and their functions
- Control sequences and troubleshooting logic
- Equipment selection for preservation applications
Domain 5: Testing & Inspection
Worth 9 scored questions, this domain evaluates your ability to verify that installed systems meet code and function correctly.
- Startup and commissioning checks
- Inspection procedures and documentation
- Identifying non-compliant installations
If you want a sense of how these domain weights translate into overall exam difficulty, read How Hard Is the OH-REF Exam? Complete Difficulty Guide 2026. For exact scoring mechanics and what 70% actually means in practice, see OH-REF Passing Score 2026: Exactly What You Need to Pass.
Eligibility and Application Mechanics
Before you can even schedule the OH-REF exam, you need to meet OCILB's eligibility requirements. The standard path requires:
- Being at least 18 years old
- U.S. citizenship or lawful status
- Five years of documented trade experience immediately preceding your application
Two alternative paths exist for candidates without the standard experience history: holding an Ohio professional engineer license along with three years of trade construction-business experience, or having five years of service as an Ohio governmental trade inspector. All applicants must submit experience documentation and pass BCI/FBI background checks as part of the application process.
For the complete list of documentation requirements and how OCILB evaluates experience, see OH-REF Requirements 2026: Eligibility, Prerequisites & How to Qualify.
Fees, Retesting, and What Everything Costs
OH-REF costs come in layered pieces, and it helps to separate exam fees from licensing fees:
- PSI exam fee: $69 per examination or retake - charged separately for the trade exam and the Business and Law exam
- Application fee: $25
- Initial license issuance fee: $25
- Liability insurance: active contractors must maintain at least $500,000 in coverage
If you fail a portion of the exam, you must wait 60 days before retesting that section, and PSI allows up to five retests per year. Each retest attempt incurs its own $69 fee, so failing a section isn't just a scheduling delay - it's a real cost consideration worth planning around. A detailed cost breakdown, including renewal fees, is available at OH-REF Certification Cost 2026: Complete Pricing Breakdown.
Approved References and Open-Book Rules
PSI's Ohio bulletin, last updated February 7, 2024, lists two approved references for the OH-REF trade exam: the 2024 Ohio Mechanical Code and Modern Refrigeration and Air Conditioning, 22nd edition. Since the exam is open-book, you're permitted to bring these approved texts into the testing room - but the rules on how you prepare them are strict.
- Advance highlighting is permitted
- Underlining is permitted
- Indexing and tabbing are permitted
- Handwritten notes are prohibited
- Additional loose papers are prohibited
This means your prep work should include physically indexing your code book and textbook weeks before test day - color-coded tabs by domain topic can save critical minutes during the 3-hour session. A quick-reference summary of these rules and other must-know facts is compiled in the OH-REF Cheat Sheet 2026: One-Page Review of Must-Know Facts.
A Domain-Weighted Study Timeline
Generic study techniques only help if they're mapped to the actual point distribution of the exam. Since Domain 1 (General Knowledge & Requirements) and Domain 4 (Refrigeration Systems & Controls) together account for 33 of the 60 scored questions, they deserve the largest blocks of your calendar.
Domain 1 - General Knowledge & Requirements
- Read and tab relevant sections of the 2024 Ohio Mechanical Code
- Build an index sheet mapping code sections to common question topics
Domain 4 - Refrigeration Systems & Controls
- Review system components and control logic in Modern Refrigeration and Air Conditioning, 22nd edition
- Practice tracing control sequences step by step
Domain 2 - Refrigeration Piping
- Focus on piping sizing and material selection rules
- Cross-reference piping code sections with your tabbed index
Domains 3 & 5 - Refrigerants, Testing & Inspection
- Cover refrigerant properties and handling safety
- Review commissioning and inspection checklists
- Take a full-length timed practice run using approved references only
Use the final days before your exam date to re-test your reference navigation speed rather than cramming new material. For a broader look at how difficult candidates find each domain in practice, review How Hard Is the OH-REF Exam? Complete Difficulty Guide 2026, and check OH-REF Exam Dates 2026: Testing Windows, Deadlines & Scheduling to plan your timeline around PSI's scheduling windows. You can also build familiarity with the question format ahead of time using the practice resources on our main practice test platform.
Don't Forget the Business and Law Exam
Passing the trade exam is only half the licensing requirement. Ohio also requires the separate Contractor's Business and Law examination, which has its own structure: 50 scored questions plus 5 pretest questions, a 2-hour time limit, and the same 70% passing requirement. It is billed and scheduled separately from the trade exam, meaning a second $69 PSI fee applies.
Many candidates underestimate this exam because it doesn't involve technical refrigeration content, but it still requires dedicated study time covering contractor obligations, licensing law, and business practice topics specific to Ohio. Treat it as a fully separate study project rather than an afterthought tacked onto trade exam prep.
After You Pass: Licensing and Renewal
Passing both exams doesn't complete the process on its own - you'll still need to finalize licensing with OCILB. Requirements include:
- Application fee: $25
- Initial license issuance fee: $25
- Maintaining at least $500,000 in liability insurance while actively licensed
- Standard annual renewal: $60, requiring 10 continuing-education hours
Ohio also offers a Compliant Contractor Program for existing licensees who qualify after a full year of good standing. Under this program, renewal options shift to either 8 continuing-education hours annually or 24 hours for a three-year renewal costing $180. This can simplify long-term renewal planning once you're established. Understanding the full lifecycle cost - from initial exam fees through years of renewal - is covered in OH-REF Certification Cost 2026: Complete Pricing Breakdown, and career outcomes are discussed in OH-REF Salary Guide 2026: Complete Earnings Analysis and Is the OH-REF Certification Worth It? Complete ROI Analysis 2026.
If you're still evaluating whether this path fits your career, browse job market context at OH-REF Jobs, or start with the fundamentals in What Is OH-REF Certification? and OH-REF Training. Once you're ready to test your knowledge under realistic conditions, practice questions modeled on the actual domain weighting are available on our practice test site.
Frequently Asked Questions
The trade exam has 60 scored questions plus 10 unscored pretest questions, for 70 total questions administered within a 3-hour time limit.
General Knowledge & Requirements carries the most weight at 18 of 60 scored questions, followed by Refrigeration Systems & Controls at 15 of 60.
No. Advance highlighting, underlining, and indexing in your approved references are permitted, but handwritten notes and additional papers are prohibited.
You must wait 60 days before retesting that section, and PSI permits up to five retests per year, each requiring a separate $69 fee.
No. It's a separate exam with 50 scored questions, a 2-hour limit, its own $69 PSI fee, and the same 70% passing requirement as the trade exam.