- The trade exam has 52 questions (50 scored) in 150 minutes; you need 70% to pass.
- General Knowledge is 32% of scored trade content - the single largest domain by far.
- PSI charges $69 per attempt; plus OCILB's $25 application and $25 issuance fees.
- Only advance highlighting, underlining, and indexing are allowed - no loose notes at the test center.
What OH-HYD Actually Tests
The Ohio Hydronics Contractor License Exam (OH-HYD) is the commercial trade licensing exam overseen by the Ohio Construction Industry Licensing Board (OCILB) under the Ohio Department of Commerce's Division of Industrial Compliance. PSI is the testing vendor that builds and delivers the exam. The trade scope is specific: steam and hot-water heating systems and chilled-water refrigeration systems - not plumbing, not electrical, not general HVAC. If a question topic falls outside that scope, it likely doesn't belong on this exam.
This page is a condensed reference for candidates who already have a study plan underway and just want the hard numbers in one place. If you haven't built that plan yet, start with the OH-HYD Study Guide 2026 for a full first-attempt strategy, or check OH-HYD Requirements 2026 to confirm you're even eligible to sit for it yet.
Fees, Format, and Timing at a Glance
Two separate exams stand between you and a license: the hydronics trade exam and the Contractor's Business and Law exam. They have different question counts, different timing, and different fee stacking. Here's the full breakdown side by side.
| Item | Hydronics Trade Exam | Business and Law Exam |
|---|---|---|
| Total Questions | 52 (50 scored, 2 pretest) | 55 (50 scored, 5 pretest) |
| Time Allowed | 150 minutes | 120 minutes |
| Passing Score | 70% | 70% |
| PSI Fee (per attempt) | $69 | $69 |
| Reference Material | Candidate-brought approved trade references | Ohio NASCLA Contractors Guide (provided, cannot be marked) |
Add the two PSI fees together and the standard route runs $138 in testing fees, on top of OCILB's own $25 application fee and $25 license issuance fee. For the complete cost picture, including renewal and CE expenses, see OH-HYD Certification Cost 2026.
Key Takeaway
Budget for four separate charges: $25 application, $69 trade exam, $69 Business and Law exam, $25 issuance. That's the real total before insurance and renewal costs even enter the picture.
Domain Weight Cheat Sheet
PSI's official bulletin allocates the 50 scored trade questions across seven content areas. These percentages exclude the two unscored pretest items and have nothing to do with the separate Business and Law exam. Memorize this table before you memorize anything else.
| 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 |
Notice that the three largest domains - General Knowledge, Heating Equipment, and Piping, Pumps, Valves - together account for 72% of scored trade questions. That's not a coincidence you can ignore; it's a study-time roadmap. A deeper walk-through of each content area, including likely question angles, is in the OH-HYD Exam Domains 2026 guide.
General Knowledge (32%)
The largest single domain by a wide margin. Expect broad-based questions drawing on the Ohio Mechanical Code, Boiler and Unfired Pressure Vessel Rules, and general hydronic system fundamentals rather than one narrow subtopic.
- Treat this as the anchor domain in your review schedule, not an afterthought
- Cross-reference code chapter numbers so you can locate answers quickly during open-book testing
Heating Equipment (20%) and Piping, Pumps, Valves (20%)
These two domains are tied for second place and together match General Knowledge in combined weight. Heating Equipment covers boiler and heating-plant components; Piping, Pumps, Valves covers system distribution hardware and hydraulic fundamentals.
- Know component function, not just terminology
- Practice locating equipment specs fast in your approved references
Venting and Controls (10% each)
Mid-weight domains that still add up to a fifth of the scored exam combined. Venting concerns exhaust and combustion-air pathways; Controls covers the sensing and regulating devices that keep hydronic systems safe and efficient.
- Don't skip these because they're smaller than the top three - 10 combined questions can decide a pass/fail margin
Tests and Inspections (6%) and Fuel Gas and Oil (2%)
The two smallest domains. Give them a lighter, targeted review pass rather than a full week of study - proportional effort matters when your time is limited.
If you're still deciding how difficult this exam is relative to your background, How Hard Is the OH-HYD Exam? walks through the format and open-book conditions in more depth, and OH-HYD Pass Rate 2026 covers what's publicly known about outcomes.
What You Can (and Cannot) Bring
This is an open-book exam, but "open book" has strict boundaries at PSI test centers. Getting this wrong on exam day can cost you materials access or worse.
- Permitted: Approved trade references, brought by the candidate, with advance highlighting, underlining, and indexing already applied.
- Prohibited: Written notes, sticky notes with text, loose papers, or anything attached to references that wasn't part of the original bound material.
- Calculator: Only the onscreen calculator provided by the testing software - no personal calculators, phones, or devices.
- Business and Law exam: The Ohio NASCLA Contractors Guide to Business, Law and Project Management (fourth edition) is provided at the center itself and must not be marked in any way.
The live PSI bulletin (cover revision dated February 7, 2024) names the specific references you'll want tabbed: 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).
Eligibility and Application Mechanics
Before you can sit for OH-HYD, OCILB has to approve your application, and that approval hinges on documented experience, not just a fee payment. The standard route requires:
- At least 18 years old, with U.S. citizenship or legal-status evidence
- Five years of trade experience immediately preceding application
- Five consecutive years of tax records supporting that experience
- One accepted supporting-document option: qualifying permits, an active trade journeyman card, an approved apprenticeship certificate, or 40 nonduplicated hours of approved live or virtual trade-code education
- Passing state and federal background checks after OCILB approval
Note that the 40-hour education option is supporting evidence, not a substitute for the five years of experience - a detail people frequently misread. Two alternative routes exist for specific backgrounds: an Ohio-registered professional engineer with three years of relevant construction-business experience, or five years as an Ohio government inspector in the trade. Full detail on each path is in OH-HYD Requirements 2026.
Key Takeaway
Your exam authorization expires one year after the completed criminal-records check is received - plan your registration and study schedule so you don't let that window lapse.
Scoring, Retest, and Expiration Rules
Both exams share a 70% passing threshold, but they're scored and retaken independently. Understanding the exact mechanics avoids surprises on exam day and after.
- Fail one portion (trade or Business and Law) and you must wait 60 days before retesting that portion
- After five total attempts without passing, you must reapply under Ohio Revised Code 4740.06 rather than simply re-registering
- Once you pass both parts and receive your license, a Business and Law pass can be carried over to count toward another approved trade examination for three years from license issuance
Full detail on how scaled scoring and question weighting work is available in OH-HYD Passing Score 2026. If you're mapping out when to register relative to background-check timing and the one-year authorization window, see OH-HYD Exam Dates 2026.
After You Pass: Insurance, Renewal, and CE
Passing the exam isn't the finish line - license issuance carries its own requirements, and staying licensed means ongoing obligations.
- License issuance requires at least $500,000 in contractor liability coverage and assignment to a contracting company
- Standard annual renewal costs $60 and requires 10 approved continuing education hours
- Licensees with one year of demonstrated compliance may apply to the Compliant Contractor Program, which offers two renewal tracks: $60 annually with 8 CE hours, or $180 every three years with 24 CE hours
For a look at how the license translates into work opportunities and who's hiring hydronics-licensed contractors in Ohio, see OH-HYD Jobs and OH-HYD Salary Guide 2026. If you're still weighing whether the licensing investment makes sense for your career stage, Is the OH-HYD Certification Worth It? breaks down the return side of that decision.
Last-Week Review Plan
If you're using this cheat sheet in the final stretch before your test date, sequence your remaining hours by domain weight rather than by chapter order in your reference books.
General Knowledge (32%)
- Review Ohio Mechanical Code and Boiler and Unfired Pressure Vessel Rules chapter organization
- Confirm your tabs let you locate any code section in under 30 seconds
Heating Equipment and Piping, Pumps, Valves (20% each)
- Drill component identification and function in the Boiler Operator's Guide
- Run practice questions on system distribution hardware
Venting and Controls (10% each)
- Review exhaust pathway rules and control-device sensing logic
- Flag any reference pages you'll need mid-exam
Tests and Inspections, Fuel Gas and Oil (6% and 2%)
- Light targeted review only - proportional to their small scored weight
- Skim Business and Law fundamentals if that exam is scheduled separately
Final Pass
- Run a full-length timed practice session on the OH-HYD practice test platform
- Re-check reference indexing and calculator familiarity
For more on structuring longer-term prep instead of a final-week cram, the OH-HYD Study Guide 2026 covers a full multi-week plan. And if you haven't logged timed practice yet, the practice test platform is the fastest way to see how your current pacing holds up against the 150-minute trade exam limit.
FAQ
52 total questions: 50 scored plus 2 unscored pretest items, delivered in 150 minutes with a 70% passing requirement.
General Knowledge, at 32% of scored trade questions - roughly 16 of the 50 scored items. Heating Equipment and Piping, Pumps, Valves each follow at 20%.
No. Written notes and loose or attached papers are prohibited. You may bring approved trade references with advance highlighting, underlining, and indexing already applied.
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 rather than simply re-registering.
PSI charges $69 per exam attempt for each of the two exams ($138 combined), plus OCILB's $25 application fee and $25 license issuance fee.