- What the 14 ACR Domains Actually Represent
- The Full Domain Breakdown at a Glance
- The Big Three: Air Distribution, Equipment Requirements and Design, HVAC Systems
- Service and Testing: The Field-Skills Domains
- The Foundational Domains You Can't Skip
- Exam Format, Fees, and Registration Mechanics
- Sequencing Your Study by Domain Weight
- Who Actually Hires for This Class A Endorsement
- Frequently Asked Questions
- Air Distribution is the single largest domain at 15% of the 120 scored items.
- Equipment Requirements and Design (11.67%) and HVAC Systems (9.17%) round out the top three domains.
- Service and Testing each carry 10%, making field-diagnostic skill nearly as important as design knowledge.
- The exam is open-book with tabbed, highlighted references allowed - but references only help if you know where to look.
What the 14 ACR Domains Actually Represent
The Texas Air Conditioning and Refrigeration (ACR) Contractor License Exam isn't organized around abstract theory - it's organized around the actual scope of work a Class A contractor performs in the field, on environmental air-conditioning systems with no equipment-size limit. TDLR and PSI built the exam outline from 14 domains, each representing a category of tasks or knowledge that a licensed contractor is expected to handle unsupervised. Every one of the 120 scored multiple-choice questions on your exam falls into one of these 14 buckets.
Understanding the domain weights isn't a nice-to-have - it's the backbone of any efficient study plan. If you spend equal time on all 14 domains, you're under-preparing for Air Distribution (15% of the exam) and over-preparing for something like Venting (4.17%). For a broader look at how domain weighting fits into an overall prep strategy, see our ACR Study Guide 2026: How to Pass on Your First Attempt.
The Full Domain Breakdown at a Glance
Below are all 14 domains as defined in PSI's official outline, calculated from the 120 scored items and rounded to two decimals. These weights reflect the exam as updated in the July 9, 2026 PSI bulletin.
| Domain | Weight | Approx. Scored Items |
|---|---|---|
| Air Distribution | 15% | ~18 |
| Equipment Requirements and Design | 11.67% | ~14 |
| HVAC Systems | 9.17% | ~11 |
| Service | 10% | ~12 |
| Testing | 10% | ~12 |
| Basic Refrigeration Components | 5% | ~6 |
| Combustion Air | 5% | ~6 |
| Controls | 5% | ~6 |
| Piping | 5% | ~6 |
| Refrigeration Principles | 5% | ~6 |
| Safety | 5% | ~6 |
| Texas Laws and Rules | 5% | ~6 |
| Ventilation | 5% | ~6 |
| Venting | 4.17% | ~5 |
Item counts above are approximations derived from applying each domain's percentage to the 120 scored questions; PSI does not guarantee an exact fixed count per form. For a deeper dive into how the score is calculated and what 70% actually means in raw terms, read ACR Passing Score 2026: Exactly What You Need to Pass.
The Big Three: Air Distribution, Equipment Requirements and Design, HVAC Systems
If you only had time to master three domains, these are the ones that move the needle most.
Domain 1: Air Distribution (15%)
The largest domain on the exam by a wide margin. Air Distribution covers duct sizing, static pressure, airflow calculations, supply and return placement, and how distribution design interacts with equipment capacity. Because it touches nearly every installation scenario, questions here often blend into other domains, meaning weak duct-sizing knowledge can cost you points in multiple sections.
- Duct sizing methods and friction rate concepts
- Static pressure troubleshooting and airflow balancing
- Supply/return design relative to load and room use
Domain 5: Equipment Requirements and Design (11.67%)
This domain tests whether you understand equipment selection and installation requirements as they apply to real jobsite conditions - clearances, mounting, condensate management, and matching equipment specs to the application. Expect scenario-based items that describe a job condition and ask what equipment configuration or clearance is code-compliant.
- Equipment clearance and access requirements
- Sizing equipment to load and application
- Condensate drainage and installation specifications
Domain 6: HVAC Systems (9.17%)
HVAC Systems covers system types, configurations, and how components work together as a whole - split systems, packaged units, heat pumps, and how each behaves under different operating conditions. This domain rewards candidates who understand system-level troubleshooting logic, not just individual part function.
- System configuration differences and use cases
- Heat pump operation in heating vs. cooling mode
- Interactions between system components under load
Key Takeaway
Because Air Distribution, Equipment Requirements and Design, and HVAC Systems together make up more than a third of the exam, any study block you build should allocate proportionally more repetitions and practice questions to these three domains than any others.
Service and Testing: The Field-Skills Domains
Service and Testing each sit at 10% - tied for the second-highest weight tier behind the big three. These domains lean heavily on applied, hands-on judgment rather than pure recall, which is part of why candidates who've spent more time in the field sometimes outperform candidates who only studied from books. If you're wondering how field experience affects exam difficulty, our guide on How Hard Is the ACR Exam? Complete Difficulty Guide 2026 breaks that down further.
Domain 10: Service (10%)
Service questions test diagnostic sequencing - how you isolate a problem, what you check first, and how you verify a repair after the fact. Expect questions built around symptom-to-cause reasoning rather than simple definitions.
- Diagnostic sequencing for common system failures
- Component-level troubleshooting logic
- Verifying repairs and system performance post-service
Domain 11: Testing (10%)
Testing covers the instruments and procedures used to verify system performance and safety - pressure testing, leak checking, and measurement interpretation. Since the exam allows a compliant nonprogrammable calculator, expect at least a few items requiring you to work through a measurement or calculation scenario.
- Pressure and leak testing procedures
- Interpreting gauge and meter readings
- Verifying airflow and system performance metrics
The Foundational Domains You Can't Skip
The remaining nine domains are each weighted at 5% or less, but collectively they still represent roughly 43% of the exam. Treating any single one as optional is a common mistake - losing points across several small domains adds up just as fast as missing a big one.
Domain 2: Basic Refrigeration Components (5%)
Covers the function and identification of core refrigeration components - compressors, condensers, evaporators, metering devices - and how each behaves within the refrigeration cycle.
Domain 3: Combustion Air (5%)
Focuses on combustion air supply requirements for gas-fired appliances, including sizing and provision of adequate air for safe combustion.
Domain 4: Controls (5%)
Tests knowledge of thermostats, relays, safety switches, and control sequencing across common HVAC control circuits.
Domain 7: Piping (5%)
Covers refrigerant and condensate piping practices, sizing, support, and installation requirements.
Domain 8: Refrigeration Principles (5%)
The theory layer beneath Domain 2 - pressure-temperature relationships, superheat, subcooling, and the refrigeration cycle's underlying physics.
Domain 9: Safety (5%)
Jobsite safety practices, refrigerant handling precautions, and electrical safety fundamentals relevant to installation and service work.
Domain 12: Texas Laws and Rules (5%)
State-specific licensing law and TDLR regulatory requirements. Worth noting: this domain is only 5% of the exam itself, but license renewal separately requires one hour of continuing education specifically on Texas law and rules each cycle - so this knowledge doesn't stop mattering after test day.
Domain 13: Ventilation (5%)
Ventilation requirements distinct from air distribution - outdoor air provisions, exhaust requirements, and code-driven ventilation minimums.
Domain 14: Venting (4.17%)
The smallest domain on the exam, covering venting requirements for gas appliances, including 2024 IMC, IFGC, and UMC reference updates taking effect September 1, 2026.
Exam Format, Fees, and Registration Mechanics
Knowing the domains only helps if you also understand the mechanics of the test day itself. The Environmental Air Class A exam is administered by PSI on behalf of TDLR and consists of 120 scored items plus 5 non-scored (unscored pretest) items, for 125 total multiple-choice questions, delivered in a 4-hour, in-person, computer-based format. You'll need 70% correct on the scored items to pass.
- TDLR application fee: $115
- PSI examination fee: $74
- Time allowed: 4 hours
- Passing score: 70%
- Format: open-book, computer-based, offered in English and Spanish
The exam is open-book, meaning approved references may be brought in - and those references can already contain preexisting notes, highlighting, underlining, and permanent tabs. A compliant nonprogrammable calculator is also permitted. This is a real advantage, but only if your references are organized around the domain weights above; flipping through an unmarked code book under a 4-hour clock wastes precious minutes. For a full cost breakdown including renewal and insurance requirements, see ACR Certification Cost 2026: Complete Pricing Breakdown.
Once licensed, the credential requires annual renewal for $65 with eight hours of continuing education, one hour of which must cover Texas law and rules. Class A contractors must also maintain commercial general liability coverage of $300,000 per occurrence, $600,000 aggregate, and $300,000 for products and completed operations - a requirement that ties directly back into why Domain 12 exists on the exam in the first place. For the latest testing windows and scheduling logistics, check ACR Exam Dates 2026: Testing Windows, Deadlines & Scheduling.
Sequencing Your Study by Domain Weight
Rather than studying domains in the order they're listed, sequence your prep by weight - heaviest first, while you have the most energy and time to build depth, then taper into the lighter domains as review rather than first-pass learning.
Air Distribution + Equipment Requirements and Design
- Work duct sizing and static pressure problems daily
- Drill equipment clearance and installation scenarios
HVAC Systems + Service
- Compare system types and heat pump modes
- Practice symptom-to-cause diagnostic questions
Testing + Refrigeration Principles + Basic Refrigeration Components
- Work pressure-temperature and superheat/subcooling calculations
- Practice gauge and meter reading interpretation
Controls, Piping, Combustion Air, Ventilation
- Cross-reference each with your tabbed code references
- Build a one-page summary sheet per domain
Safety, Texas Laws and Rules, Venting + Full Review
- Finish smallest domains and revisit weak spots
- Take full-length timed practice exams under 4-hour conditions
This isn't a generic study calendar - it's built directly around the fact that the top five domains (Air Distribution, Equipment Requirements and Design, HVAC Systems, Service, Testing) make up roughly 56% of your score, while the bottom nine domains combined make up the remaining 44%. For more on how candidates typically perform against this structure, review ACR Pass Rate 2026: What the Data Shows.
Who Actually Hires for This Class A Endorsement
The Class A designation under this exam covers environmental air-conditioning work with no equipment-size limit, which makes it relevant to a wide range of employers - from residential and light commercial HVAC contractors to companies handling larger commercial systems. Business owners pursuing their own contractor license, technicians moving into a supervisory or ownership role, and companies that need a licensed Class A holder on staff to legally pull permits are the primary candidates sitting for this exam. If you're still mapping out whether this path fits your career goals, Is the ACR Certification Worth It? Complete ROI Analysis 2026 and ACR Salary Guide 2026: Complete Earnings Analysis are useful next reads.
Whatever your motivation, the domains above are the actual content you'll be tested on - not a generic HVAC overview, but the specific scope TDLR and PSI use to determine whether you're ready to hold a Class A license. Running through timed, domain-weighted practice questions on our full-length ACR practice tests is the most direct way to see where your knowledge holds up against each of the 14 areas before test day.
Frequently Asked Questions
Start with Air Distribution since it's the largest domain at 15% of the exam, followed by Equipment Requirements and Design at 11.67%. These two alone represent more than a quarter of your scored items.
Yes. PSI builds each exam form from the official outline covering all 14 domains, with item counts proportional to the published percentages, out of 120 scored and 5 non-scored questions.
Yes, the exam is open-book. Approved references may include preexisting notes, highlighting, underlining, and permanent tabs, and a compliant nonprogrammable calculator is also allowed.
Yes. Even though it's only 5% of the exam, license renewal requires eight hours of continuing education every year, including one hour specifically on Texas law and rules.
See our ACR Cheat Sheet 2026: One-Page Review of Must-Know Facts for a quick-reference version of the domain weights and key concepts covered in this guide.