- OH-REF is the Ohio Refrigeration Contractor License Exam, regulated by OCILB and delivered by PSI.
- The trade exam has 60 scored questions (plus 10 pretest), a 3-hour limit, and a 70% passing score.
- General Knowledge & Requirements carries the most weight at 18 of 60 scored questions.
- Business and Law is a separate 50-question exam with its own $69 PSI fee and 70% passing requirement.
What Is OH-REF?
OH-REF stands for the Ohio Refrigeration Contractor License Exam, the trade examination that candidates must pass to hold a refrigeration contractor license in the state of Ohio. This is not an HVAC comfort-cooling credential - the scope is specifically focused on food and product preservation refrigeration, meaning the systems that keep commercial coolers, walk-ins, freezers, and process-cooling equipment running correctly and safely.
The exam is developed under the authority of the Ohio Construction Industry Licensing Board (OCILB) and administered through the testing vendor PSI. Passing it is one part of a larger licensing process that also includes a separate Business and Law examination, background checks, and documented trade experience. If you're just starting to research this credential, the OH-REF Requirements 2026 guide walks through eligibility in more depth, and the OH-REF Certification overview covers the full licensing path end to end.
Who Governs and Administers It
The Ohio Construction Industry Licensing Board (OCILB), housed within the Ohio Department of Commerce's Division of Industrial Compliance, sets the licensing rules for refrigeration contractors. PSI is the third-party testing provider that builds, schedules, and proctors the actual computer-based exam sessions.
These two organizations have distinct roles worth understanding:
- OCILB establishes eligibility rules, reviews experience documentation, issues licenses, and sets renewal and continuing-education requirements.
- PSI publishes the official candidate information bulletin, schedules test appointments, collects exam fees, and delivers the computer-based test at approved locations.
The current PSI bulletin (updated February 7, 2024) is the authoritative source for exam content outlines, approved references, and testing rules. If any third-party guide - including this one - ever conflicts with the current bulletin, the bulletin governs.
Exam Format and Scoring
The OH-REF trade exam is delivered as a computer-based, open-book test. Candidates are given 70 total questions - 60 scored plus 10 unscored pretest items mixed in without identification - and a 3-hour time limit. A passing score requires 70% correct on the scored portion.
Because the pretest questions are indistinguishable from scored ones, candidates should treat every question on screen with equal seriousness rather than trying to guess which items "don't count."
Key Takeaway
Budget your 3 hours across 60 scored questions - roughly 3 minutes per question - but expect to move faster on straightforward code and terminology questions to leave time for multi-step system and piping calculations.
Only PSI's onscreen calculator is permitted during testing; outside calculators are not allowed. The exam is open-book, but reference materials must be pre-approved, and while highlighting, underlining, and indexing done in advance are permitted, handwritten notes and loose additional papers are prohibited. For a full breakdown of what "passing" actually requires numerically, see the OH-REF Passing Score 2026 guide.
The Five OH-REF Domains
The 60 scored questions are distributed across five content domains. Understanding this weighting is the single most useful thing a candidate can do before opening a textbook, because it tells you exactly where your study hours produce the greatest return.
| Domain | Scored Questions | Share of Exam |
|---|---|---|
| 1. General Knowledge & Requirements | 18 | Largest domain |
| 2. Refrigeration Piping | 12 | Second-largest |
| 3. Refrigerants | 6 | Smallest |
| 4. Refrigeration Systems & Controls | 15 | Second overall |
| 5. Testing & Inspection | 9 | Moderate |
Domain 1: General Knowledge & Requirements
This is the largest domain at 18 of 60 scored questions, so it deserves the most study time. It covers the regulatory and code-based knowledge a licensed refrigeration contractor is expected to know before ever touching a system.
- Ohio Mechanical Code provisions relevant to refrigeration installation and service
- Licensing, permitting, and jurisdictional requirements
- General safety practices around refrigeration equipment
Domain 2: Refrigeration Piping
At 12 of 60 questions, piping design and installation is the second-largest domain. Expect questions on line sizing, materials, joining methods, and support requirements for refrigerant piping systems.
- Suction, discharge, and liquid line sizing considerations
- Proper piping practices to prevent oil return and refrigerant migration issues
Domain 3: Refrigerants
This is the smallest domain at 6 of 60 questions but still requires precise knowledge of refrigerant properties, handling, and recovery obligations tied to preservation-focused refrigeration equipment.
- Refrigerant classifications and characteristics
- Recovery, handling, and environmental compliance basics
Domain 4: Refrigeration Systems & Controls
With 15 of 60 questions, this is the second-heaviest domain overall. It covers the mechanical and control components that keep commercial refrigeration systems operating within design parameters.
- Compressors, evaporators, condensers, and expansion devices
- Controls governing defrost cycles, temperature, and safety cutouts
Domain 5: Testing & Inspection
This 9-of-60 domain focuses on verifying that installed systems perform correctly and meet code before and after commissioning.
- Leak testing and pressure verification procedures
- Inspection sign-off and documentation expectations
For a deeper walkthrough of each content area with more example topics, the OH-REF Exam Domains 2026 guide expands on all five areas in detail.
The Business and Law Companion Exam
OH-REF licensure requires passing a second, separate exam: the Contractor's Business and Law examination. This is distinct from the trade exam and is scored independently.
- 50 scored questions plus 5 unscored pretest questions (55 total administered)
- 2-hour time limit
- 70% passing requirement, same threshold as the trade exam
- Charged separately at PSI's standard exam fee - it is not bundled with the trade exam fee
Candidates sometimes assume passing the trade exam alone is sufficient. It is not - both exams must be passed independently to qualify for licensure.
Eligibility and Application
Before scheduling either exam, candidates must meet OCILB's eligibility rules. The standard path requires:
- Age 18 or older
- U.S. citizenship or documented lawful status
- Five years of documented trade experience immediately preceding the application
Two alternative paths exist for candidates who don't meet the standard experience route:
- Holding an Ohio professional engineer license, combined with three years of trade construction-business experience
- Five years of experience as an Ohio governmental trade inspector
All applicants must submit experience documentation and complete BCI/FBI background checks as part of the application process. For a section-by-section look at how these requirements apply to different candidate backgrounds, see OH-REF Requirements 2026: Eligibility, Prerequisites & How to Qualify.
Fees, Insurance, and Renewal
OH-REF licensing involves several distinct costs that candidates should plan for separately, since they aren't bundled into a single payment.
- $69 per PSI exam attempt or retake - charged separately for the trade exam and the Business and Law exam
- $25 application fee to OCILB
- $25 for initial license issuance
- Active contractors must maintain at least $500,000 of liability insurance
- $60 standard annual renewal, requiring 10 continuing-education hours
Ohio's Compliant Contractor Program offers an alternative renewal structure for licensees who qualify after a compliant year: 8 continuing-education hours for annual renewal, or 24 hours for a three-year renewal costing $180. A full cost breakdown, including how these figures compare across renewal cycles, is available in the OH-REF Certification Cost 2026 breakdown.
If a portion of either exam is failed, PSI requires a 60-day wait before retesting that portion, and candidates may retest up to five times per year.
Who Needs OH-REF and Who Hires For It
This license applies to contractors who install, service, or maintain commercial refrigeration equipment used for food and product preservation - not comfort-cooling HVAC systems. Employers and clients likely to require or prefer OH-REF licensure include:
- Commercial refrigeration service and installation companies
- Grocery, convenience store, and food-service chains needing licensed contractors for walk-in coolers and freezer systems
- General mechanical contractors that subcontract refrigeration-specific work
- Facilities and cold-storage operators requiring licensed maintenance providers
Because Ohio law requires the license for this scope of work, holding it is often a baseline requirement rather than a differentiator among competing bids. To understand how this credential factors into career and compensation decisions, see the OH-REF Salary Guide 2026 and the ROI analysis on whether OH-REF certification is worth it. For active postings and hiring trends, the OH-REF Jobs page tracks where licensed contractors are in demand.
Building a Study Plan Around the Domains
Because the trade exam's five domains carry very different point values, an efficient study plan allocates time proportionally rather than spending equal effort everywhere. A candidate with limited weeks before a scheduled test date benefits most from front-loading Domain 1 (General Knowledge & Requirements) and Domain 4 (Refrigeration Systems & Controls), since together they account for 33 of the 60 scored questions.
General Knowledge & Requirements
- Review Ohio Mechanical Code sections relevant to refrigeration
- Study licensing and permitting requirements
Refrigeration Systems & Controls + Piping
- Work through compressor, evaporator, and control component questions
- Practice line-sizing and piping installation scenarios
Refrigerants and Testing & Inspection
- Cover refrigerant handling and recovery rules
- Review leak testing and inspection sign-off procedures
Full Review and Mock Testing
- Run timed practice sessions to build 3-hour pacing habits
- Revisit weaker domains identified during practice
This kind of proportional scheduling - combined with reviewing your approved reference materials (the 2024 Ohio Mechanical Code and Modern Refrigeration and Air Conditioning, 22nd edition) - is covered in more depth in the OH-REF Study Guide 2026. If you want a sense of how demanding the exam actually feels once you're inside the 3-hour window, the How Hard Is the OH-REF Exam? guide breaks that down further, and OH-REF Pass Rate 2026: What the Data Shows discusses what's publicly known about outcomes.
Practicing under realistic question formats matters as much as reviewing content. Running through timed questions on our OH-REF practice test platform before test day helps confirm your pacing and flags domains that need another pass before you sit for the real thing at a PSI test center.
Frequently Asked Questions
No. OH-REF licenses contractors specifically for food and product preservation refrigeration systems, not comfort-cooling HVAC work. The domains focus on commercial refrigeration piping, systems, controls, and refrigerants.
Yes. The trade exam (60 scored questions, 3-hour limit) and the Business and Law exam (50 scored questions, 2-hour limit) are separate tests, each requiring 70% to pass, and each charged its own $69 PSI fee.
You must wait 60 days before retesting that failed portion. PSI allows up to five retest attempts within a year.
The exam is open-book with approved references, and advance highlighting, underlining, and indexing are allowed. However, handwritten notes and separate papers are prohibited, and only PSI's onscreen calculator may be used.
Standard eligibility requires five years of documented trade experience immediately preceding application, along with meeting age and citizenship/lawful-status requirements. Alternative paths exist for Ohio-licensed professional engineers and governmental trade inspectors.