- OH-HYD is the Ohio Hydronics Contractor License Exam, administered by PSI for OCILB commercial licensing.
- The trade exam has 52 questions (50 scored) with 150 minutes and a 70% passing score.
- General Knowledge (32%), Heating Equipment (20%), and Piping, Pumps, Valves (20%) make up 72% of scored content.
- Standard testing fees total $138 when combining the trade exam and Business and Law exam.
What Is OH-HYD?
OH-HYD is the shorthand used on this site for the Ohio Hydronics Contractor License Exam - the trade examination that commercial contractors in Ohio must pass to become licensed in the hydronics specialty. This exam covers steam and hot-water heating systems as well as chilled-water refrigeration systems, and it is one piece of a licensing process overseen by the Ohio Construction Industry Licensing Board (OCILB), a unit of the Ohio Department of Commerce's Division of Industrial Compliance.
If you've searched other sites and found conflicting fee amounts, question counts, or governing bodies, be aware that "OH-HYD" is used by more than one credential elsewhere. Everything on this page refers exclusively to the Ohio commercial hydronics contractor license administered through PSI testing centers. For a deeper look at what the credential unlocks professionally, see OH-HYD Certification.
Who Oversees the Exam
OCILB sets the licensing rules and experience requirements, while PSI is the third-party testing vendor that builds, delivers, and scores the actual examination at its computer-based test centers. This split matters for candidates: OCILB approves your application and background checks before you're ever authorized to sit for the exam, and PSI controls everything about the day-of testing experience - check-in, allowed materials, the onscreen calculator, and your score report.
The current PSI candidate bulletin governing this exam carries a February 7, 2024 cover revision. It references Ohio Administrative Code Chapter 4101:4 (Boiler and Unfired Pressure Vessel Rules, 2015), the Ohio Mechanical Code (2024), and the Boiler Operator's Guide (fourth edition 1998 or fifth edition 2020) as the reference texts the exam draws from. If you want the full list of statutory and rule citations behind the license, review Ohio Revised Code 4740.06 and Ohio Administrative Code 4101:16-1 and 4101:16-2 directly.
Exam Format and Question Style
The Hydronics trade exam is computer-based, multiple-choice, and open-book - but "open-book" here has specific rules. You may bring approved trade references, and you're allowed to highlight, underline, and index those references in advance. What you cannot bring are written notes or extra loose/attached papers. The only calculator permitted is the one provided onscreen by PSI; personal calculators are not allowed.
- Total questions: 52 (50 scored, 2 unscored pretest items you can't identify)
- Time allowed: 150 minutes
- Passing score: 70%
There's a separate Business and Law exam most applicants also need: 55 questions (50 scored, 5 unscored), 120 minutes, and its own independent 70% passing threshold. For that portion, PSI provides the Ohio NASCLA Contractors Guide to Business, Law and Project Management (fourth edition) at the test center - you cannot mark it up like your trade references. For a full walkthrough of scoring mechanics, see OH-HYD Passing Score 2026: Exactly What You Need to Pass.
Key Takeaway
Prep your trade reference materials (highlighting, tabs, indexing) well before test day - that's the only "notes" advantage you're allowed, since loose papers and handwritten notes are prohibited.
Domain Breakdown
PSI allocates the 50 scored trade questions across seven content domains. These percentages exclude the two pretest items and have nothing to do with the separate Business and Law exam.
| Domain | Weight | Approx. Scored Questions |
|---|---|---|
| General Knowledge | 32% | 16 |
| Heating Equipment | 20% | 10 |
| Piping, Pumps, Valves | 20% | 10 |
| Venting | 10% | 5 |
| Controls | 10% | 5 |
| Tests and Inspections | 6% | 3 |
| Fuel Gas and Oil | 2% | 1 |
Three domains - General Knowledge, Heating Equipment, and Piping, Pumps, Valves - account for 72% of the scored trade questions. That concentration should shape how you allocate study time. A full domain-by-domain breakdown with subtopics lives in OH-HYD Exam Domains 2026: Complete Guide to All 7 Content Areas.
General Knowledge (32%)
The largest single domain, drawing broadly from Ohio Mechanical Code provisions, boiler and pressure vessel rules, and general hydronics system principles.
- Ohio Administrative Code 4101:4 boiler/pressure vessel rules
- Ohio Mechanical Code fundamentals
- System-level terminology and safety concepts
Heating Equipment (20%)
Covers boilers, water heaters, and related heating equipment used in steam and hot-water systems.
- Boiler types and operating principles
- Equipment sizing and application basics
- Content sourced from the Boiler Operator's Guide references
Piping, Pumps, Valves (20%)
Focuses on the distribution side of hydronic systems - how heated or chilled water/steam actually moves through a building.
- Piping materials and layout practices
- Pump selection and circulation concepts
- Valve types and their functions in hydronic loops
The remaining four domains - Venting, Controls, Tests and Inspections, and Fuel Gas and Oil - carry smaller weights but shouldn't be skipped, since even a 1-question domain can be the difference at the 70% cutoff. For an honest assessment of how tough this mix actually is to prepare for, see How Hard Is the OH-HYD Exam? Complete Difficulty Guide 2026.
Fees and Registration Mechanics
Understanding the fee structure helps you budget and avoid surprise costs. OCILB charges $25 for the examination application and another $25 for license issuance once you've passed. PSI, separately, charges $69 per exam registration or attempt. Since most applicants sit for both the trade exam and the Business and Law exam, the standard testing-fee total comes to $138 (two $69 PSI registrations), on top of the OCILB application and issuance fees.
A full breakdown of every fee, renewal cost, and optional program is covered in OH-HYD Certification Cost 2026: Complete Pricing Breakdown. Once licensed, standard annual renewal is $60 with ten approved continuing education hours; the Compliant Contractor Program offers an alternative for eligible licensees at $60/year (8 CE hours) or $180 every three years (24 CE hours) after one year of demonstrated compliance.
Eligibility Basics
Before you can even schedule a PSI exam date, OCILB has to approve your application. At a minimum, applicants must be 18 or older, provide required U.S. citizenship or legal-status evidence, and satisfy trade experience requirements - followed by state and federal background checks.
- Standard route: five years of trade experience immediately before application, five consecutive years of tax records, plus one accepted supporting document - qualifying permits, an active trade journeyman card, an approved apprenticeship certificate, or 40 nonduplicated hours of approved live/virtual trade-code education.
- Professional engineer route: an Ohio-registered PE with three years of relevant construction-business experience.
- Government inspector route: five years as an Ohio government inspector in the trade.
Note that the 40-hour education option is supporting evidence for the standard route, not a substitute for the five years of trade experience itself. Once your criminal-records check is complete, your exam authorization is valid for one year. A failed portion requires a 60-day wait before you can retest, and if you haven't passed after five attempts, you must reapply under Ohio Revised Code 4740.06. Full eligibility detail, including document specifics, is in OH-HYD Requirements 2026: Eligibility, Prerequisites & How to Qualify.
Who Hires Licensed Hydronics Contractors
Because the license is scoped specifically to steam, hot-water heating, and chilled-water refrigeration systems, the demand for it clusters around commercial mechanical contracting firms, HVAC companies with commercial boiler divisions, and facilities/plant operations teams responsible for large-building heating plants. Licensed Ohio commercial contractors need this credential - or one of the other OCILB trade specialties plus Business and Law - to legally pull permits and contract commercial hydronics work in the state.
Employers evaluating candidates for these roles typically care about the license status itself (active, in good standing, backed by the required $500,000 in contractor liability coverage) and the assigned contracting company on file with OCILB, since license issuance requires both. If you're weighing whether pursuing this license is worth the time and cost against your career goals, Is the OH-HYD Certification Worth It? Complete ROI Analysis 2026 and OH-HYD Salary Guide 2026: Complete Earnings Analysis dig into that question further, and OH-HYD Jobs looks at where licensed contractors typically find work.
Scheduling Your Prep Around the Domains
Generic study techniques only help if you point them at the right material. Given that General Knowledge, Heating Equipment, and Piping, Pumps, Valves together make up 72% of the scored trade exam, your weekly plan should weight those domains heavily before you spend equal time on Fuel Gas and Oil, which contributes just one scored question.
General Knowledge foundations
- Work through Ohio Administrative Code 4101:4 and the Ohio Mechanical Code sections most cited in the bulletin
- Build your tabbed, highlighted reference set for open-book use
Heating Equipment and Piping/Pumps/Valves
- Study boiler types and operation from the Boiler Operator's Guide
- Review piping layout, pump selection, and valve function scenarios
Venting and Controls
- Cover venting requirements and control system logic - each worth 10%
- Practice timed question sets that mix these with the larger domains
Tests, Inspections, Fuel Gas/Oil, and Business and Law
- Finish the smaller-weight trade domains
- Shift focus to the Business and Law exam using the NASCLA guide format
For a structured, week-by-week plan built entirely around this domain weighting, see OH-HYD Study Guide 2026: How to Pass on Your First Attempt. A condensed one-page review of the facts that show up most often is available in OH-HYD Cheat Sheet 2026: One-Page Review of Must-Know Facts, and you can run realistic timed questions on our practice test platform before booking your PSI appointment.
After You Pass
Passing both the trade exam and Business and Law exam doesn't automatically make you licensed - you still need to secure at least $500,000 in contractor liability coverage and be assigned to a contracting company before OCILB issues the license. One helpful detail: if you've already passed Business and Law and later pursue another approved OCILB trade exam, that Business and Law pass can carry over for three years from your license issuance date, so you won't need to retake it immediately for a second trade license.
Once licensed, mark your renewal calendar - $60 annually with ten CE hours under the standard path, or explore the Compliant Contractor Program option after a year of good standing. If you're still mapping out when to schedule your first attempt around PSI availability and the one-year authorization window, OH-HYD Exam Dates 2026: Testing Windows, Deadlines & Scheduling covers the timing logistics, and OH-HYD Pass Rate 2026: What the Data Shows looks at what's publicly known about outcomes.
Frequently Asked Questions
On this site, OH-HYD refers to the Ohio Hydronics Contractor License Exam, the PSI-administered trade exam required for OCILB commercial hydronics contractor licensing in Ohio.
The trade exam has 52 total questions - 50 scored and 2 unscored pretest items - with 150 minutes allowed and a 70% passing requirement.
Yes, it's computer-based, multiple-choice, and open-book at PSI centers. You may bring approved trade references with advance highlighting, underlining, and indexing, but not loose notes or extra papers, and only the onscreen calculator is allowed.
Most applicants also take the separate Business and Law exam: 55 questions (50 scored, 5 unscored), 120 minutes, with its own independent 70% passing score.
You must wait 60 days before retesting that portion. If you haven't passed after five total attempts, you must reapply under Ohio Revised Code 4740.06.