- What the OH-HYD Certification Actually Covers
- Who Issues the License and Who Administers the Exam
- Exam Format: Two Separate Tests, Two Separate Clocks
- The Seven Content Domains, Weighted
- Fees and the Registration Path
- Eligibility Routes Into the Exam
- Retest Rules and Authorization Windows
- After You Pass: License, Insurance, Renewal
- Building a Study Plan Around the Domain Weights
- Who Hires OH-HYD-Licensed Contractors
- Frequently Asked Questions
- The trade exam has 52 questions (50 scored, 2 pretest) in 150 minutes; you need 70% to pass.
- General Knowledge, Heating Equipment, and Piping/Pumps/Valves make up 72% of scored trade content.
- PSI charges $69 per exam attempt; the standard trade-plus-Business-and-Law route costs $138 in testing fees.
- License issuance requires at least $500,000 in contractor liability coverage plus assignment to a contracting company.
What the OH-HYD Certification Actually Covers
The OH-HYD credential - the Ohio Hydronics Contractor License Exam - is the state's commercial contractor licensing exam for the hydronics trade. That trade scope specifically includes steam and hot-water heating systems and chilled-water refrigeration systems. It is not a general HVAC test, and it is not the same as any nationally branded "OH-HYD" designation you might find under a different administering body elsewhere. If you're still getting oriented, the companion pieces What Is OH-HYD?, OH-HYD Meaning, and What Does OH-HYD Stand For? walk through the terminology in more depth.
Passing the exam is one part of a larger licensing process run through Ohio's construction industry licensing structure. The written test itself is computer-based, multiple-choice, and open-book - but "open-book" here means approved trade references only, not free-form notes. For a full breakdown of everything a candidate needs before test day, see OH-HYD Requirements 2026: Eligibility, Prerequisites & How to Qualify.
Who Issues the License and Who Administers the Exam
Licensing authority sits with the Ohio Construction Industry Licensing Board (OCILB), which operates under the Ohio Department of Commerce's Division of Industrial Compliance. OCILB sets the eligibility rules and approves applicants; PSI is the third-party testing vendor that actually administers the Hydronics Contractor examination at its test centers.
Exam Format: Two Separate Tests, Two Separate Clocks
Most candidates sit for two exams, not one:
- Hydronics trade exam: 52 total questions - 50 scored plus 2 unscored pretest items - with 150 minutes allowed and a 70% passing requirement.
- Contractor's Business and Law exam: 55 total questions - 50 scored plus 5 unscored - with 120 minutes allowed and its own separate 70% passing requirement.
Both are computer-based and multiple-choice, delivered at PSI test centers. The only calculator permitted is the onscreen tool provided by the testing software; outside calculators are not allowed. For the finer print on how the score is calculated and what "70%" actually means in scored-item terms, see OH-HYD Passing Score 2026: Exactly What You Need to Pass.
Key Takeaway
Treat the trade exam and the Business and Law exam as two separate study projects with two separate pass/fail outcomes - a strong trade score does not offset a weak Business and Law score, and vice versa.
Reference Materials: What You Can and Can't Bring
For the trade exam, candidates bring their own approved trade references. The live PSI bulletin (cover-revised February 7, 2024) lists 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 referenced texts. You're allowed to highlight, underline, and index those books in advance - but written notes and loose or attached papers of any kind are prohibited.
For the Business and Law exam, the reference book - the Ohio NASCLA Contractors Guide to Business, Law and Project Management, fourth edition - is provided at the test center itself, and it must not be marked in any way.
The Seven Content Domains, Weighted
PSI's official item allocation across the 50 scored trade questions breaks down into seven domains. These weights exclude pretest items and have nothing to do with the separate Business and Law exam.
Domain 1: General Knowledge (32%)
The single largest domain by a wide margin - roughly one-third of the scored trade questions. Candidates should expect broad coverage of fundamental hydronics principles, terminology, and code-driven basics that cut across the rest of the exam.
- Foundational vocabulary and system concepts referenced throughout other domains
Domain 2: Heating Equipment (20%)
Boilers, water heaters, and related heating equipment used in steam and hot-water systems fall here.
- Equipment selection, installation, and code compliance basics
Domain 3: Piping, Pumps, Valves (20%)
The mechanical backbone of any hydronics system - sizing, materials, circulation, and control components.
- Piping layout logic, pump function, and valve types/applications
Domain 4: Fuel Gas and Oil (2%)
The smallest domain on the exam, but still tested - don't skip it entirely just because the weight is low.
Domain 5: Venting (10%)
Proper venting practices for combustion equipment and system safety.
Domain 6: Controls (10%)
Control systems that regulate temperature, pressure, and flow within hydronics installations.
Domain 7: Tests and Inspections (6%)
Verification and inspection procedures that confirm a system was installed and functions correctly.
Notice that General Knowledge, Heating Equipment, and Piping/Pumps/Valves together account for 72% of scored trade questions. That concentration should directly shape how you allocate study time. For a deeper domain-by-domain walkthrough with more subtopic detail, see OH-HYD Exam Domains 2026: Complete Guide to All 7 Content Areas.
| Domain | Scored Weight |
|---|---|
| General Knowledge | 32% |
| Heating Equipment | 20% |
| Piping, Pumps, Valves | 20% |
| Venting | 10% |
| Controls | 10% |
| Tests and Inspections | 6% |
| Fuel Gas and Oil | 2% |
Fees and the Registration Path
Budgeting for OH-HYD licensure involves more than one line item:
- $25 - OCILB examination application fee
- $25 - OCILB license issuance fee
- $69 - PSI fee per exam registration/attempt (charged separately for the trade exam and for Business and Law)
The standard trade-plus-Business-and-Law testing route runs $138 in PSI fees alone, before Board fees. A full cost breakdown, including what happens financially if you need to retest, is covered in OH-HYD Certification Cost 2026: Complete Pricing Breakdown.
Eligibility Routes Into the Exam
Candidates must be at least 18 years old, provide required evidence of U.S. citizenship or legal status, meet experience requirements, and secure OCILB approval before completing state and federal background checks and sitting for testing. The standard route requires:
- Five years of trade experience immediately preceding application
- Five consecutive years of tax records
- 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
That 40-hour education option is supporting evidence for the experience requirement - it is not a stand-alone prerequisite and does not replace the five years of experience itself. Alternative eligibility routes exist for an Ohio-registered professional engineer with three years of relevant construction-business experience, or for someone with five years as an Ohio government inspector in the trade. The full eligibility mechanics, including document specifics, are laid out in OH-HYD Requirements 2026: Eligibility, Prerequisites & How to Qualify.
Retest Rules and Authorization Windows
Once your criminal-records check is complete, examination authorization expires one year after that check is received - so don't let approval sit unused. If you fail a portion of the exam, you must wait 60 days before retesting that portion. If you reach five total examination attempts without passing, you can't simply keep retrying; you must reapply under Ohio Revised Code 4740.06. That's a materially different process than a routine retake, so it's worth understanding before you burn through attempts casually.
Key Takeaway
Every failed attempt costs another $69 PSI fee and a mandatory 60-day wait - first-attempt preparation is meaningfully cheaper and faster than repeat testing.
If you want an honest assessment of how demanding the exam actually is before you commit to a testing date, How Hard Is the OH-HYD Exam? Complete Difficulty Guide 2026 and OH-HYD Pass Rate 2026: What the Data Shows both go into more detail than we can cover here.
After You Pass: License, Insurance, Renewal
Passing both exams is not the finish line by itself. License issuance also requires at least $500,000 in contractor liability coverage and assignment to a contracting company. Once licensed, standard annual renewal costs $60 and requires ten approved continuing education hours.
Ohio also runs a Compliant Contractor Program for eligible existing licensees who demonstrate one year of compliance. Approved members can choose between renewing annually for $60 with eight CE hours, or renewing every three years for $180 with 24 CE hours - a longer-cycle option that can simplify recordkeeping for established contractors.
Building a Study Plan Around the Domain Weights
Generic study techniques - spaced repetition, timed practice blocks, flashcard review - only help if they're pointed at the right material in the right proportion. Given that General Knowledge, Heating Equipment, and Piping/Pumps/Valves make up 72% of the scored trade exam, a sensible plan front-loads those three domains before spending equal time on Fuel Gas and Oil, which carries only 2% weight.
General Knowledge and Heating Equipment
- Work through Ohio Mechanical Code sections relevant to hydronics fundamentals
- Review boiler and water-heater equipment topics from the Boiler Operator's Guide
Piping, Pumps, Valves
- Drill sizing, materials, and component function questions
- Cross-reference Chapter 4101:4 rules on pressure vessels and piping
Venting and Controls
- Split time evenly - each carries 10% weight
Tests and Inspections, Fuel Gas and Oil, and Business and Law prep
- Light review of the smaller-weight domains
- Shift focus to the separate NASCLA Business and Law content
For a structured, week-by-week walkthrough with more resource detail, see OH-HYD Study Guide 2026: How to Pass on Your First Attempt. And if you just need a fast final-review reference the night before test day, OH-HYD Cheat Sheet 2026: One-Page Review of Must-Know Facts condenses the highest-yield facts.
Who Hires OH-HYD-Licensed Contractors
An OH-HYD license qualifies a contractor to bid and perform commercial hydronics work in Ohio - installation and service of steam and hot-water heating systems and chilled-water refrigeration systems. This makes the license relevant to mechanical contracting firms, commercial boiler service companies, and facilities-management operations that maintain hydronic plants in institutional or commercial buildings. If you're evaluating whether the license is worth pursuing relative to the time and fees involved, Is the OH-HYD Certification Worth It? Complete ROI Analysis 2026 and OH-HYD Salary Guide 2026: Complete Earnings Analysis dig into that question directly, and OH-HYD Jobs looks at the kinds of roles the license opens up.
Before you schedule anything, it's worth confirming current testing windows through OH-HYD Exam Dates 2026: Testing Windows, Deadlines & Scheduling, since PSI center availability and Board processing timelines both affect when you can realistically sit for the exam. You can also practice the format itself at our practice test platform before committing to a test date, and revisit the main practice site periodically as you work through each domain.
Frequently Asked Questions
Yes, but only with approved trade references - the Ohio Administrative Code Chapter 4101:4 rules, the Ohio Mechanical Code, and the Boiler Operator's Guide. You may highlight, underline, and index these in advance, but loose notes and additional papers are not allowed.
They are separate exams with separate question counts, time limits, and 70% passing thresholds. You register and pay for each one individually through PSI.
You must wait 60 days before retesting that portion, and you'll pay the $69 PSI fee again. After five total attempts without passing, reapplication must go through the process defined in Ohio Revised Code 4740.06.
General Knowledge, since it's the largest single domain at 32% of scored trade questions, followed by Heating Equipment and Piping, Pumps, Valves at 20% each - together these three make up 72% of the trade exam.
No. Only the onscreen calculator provided within the PSI testing software is permitted during the computer-based exam.