- Exam Overview and Why Domains Matter
- Domain 1: Electrical Knowledge, Motors, and Controls
- Domain 2: Piping
- Domain 3: Refrigeration and Air Conditioning
- Domain 4: Heating Systems
- Domain 5: Air Distribution Systems
- Domain 6: Safety
- Full Domain Allocation Table
- Mapping a Study Timeline to the Blueprint
- FAQ
- Refrigeration and Air Conditioning carries 25 of 100 questions - the single largest domain.
- Electrical Knowledge and Heating Systems each carry 20 questions; Piping and Air Distribution each carry 15.
- Safety is the smallest domain at just 5 questions, but it still requires solid OSHA 29 CFR 1926 knowledge.
- The exam is open-book, computer-administered, 100 questions, 240 minutes, with a 70% passing standard.
Exam Overview and Why Domains Matter
The Maryland Journeyman HVACR License Exam (MD-JHVACR), administered through PSI Services LLC on behalf of the Maryland Board of Heating, Ventilation, Air Conditioning and Refrigeration Contractors, is built from six defined content areas. Each domain carries a fixed number of the exam's 100 multiple-choice questions, and the Board-linked PSI bulletin (updated September 1, 2024) spells out exactly how those questions are distributed. Understanding this breakdown is the fastest way to decide where your study hours actually pay off.
If you haven't yet reviewed the broader exam structure, our MD-JHVACR Study Guide 2026 walks through the full first-attempt strategy, and the MD-JHVACR Requirements guide covers eligibility in detail. This article focuses specifically on the six content domains themselves - what's tested, how heavily, and what a Maryland apprentice needs to know before scheduling.
Domain 1: Electrical Knowledge, Motors, and Controls
Electrical Knowledge, Motors, and Controls accounts for 20 of the 100 exam questions, making it tied for the second-largest domain on the blueprint. This section tests a journeyman's ability to work confidently with the electrical side of HVACR systems - the wiring, motors, and control logic that keep equipment running safely.
Electrical Knowledge, Motors, and Controls
Candidates should be able to interpret wiring diagrams, size and troubleshoot single- and three-phase motors, and understand control circuits used in residential and light commercial HVACR equipment.
- Motor types, starting methods, and overload protection
- Control circuits: relays, contactors, transformers, and thermostats
- Basic circuit calculations - voltage, amperage, and resistance relationships
- Troubleshooting logic for electrical faults in HVACR equipment
Because this domain overlaps with real field diagnostics, questions tend to be scenario-based rather than pure definition recall. Expect to apply concepts to a described symptom (a motor that hums but won't start, a control that won't energize) rather than just naming a component.
Domain 2: Piping
Piping makes up 15 of the 100 questions. This domain covers the materials, joining methods, and layout principles used across refrigerant lines, condensate drainage, and fuel or water piping connected to HVACR systems.
Piping
Expect questions on pipe sizing, support spacing, and the correct method for a given material and application.
- Copper, steel, and plastic piping applications in HVACR work
- Joining methods: brazing, soldering, threading, and solvent welding
- Condensate drain sizing and slope requirements
- Refrigerant line sizing considerations tied to system capacity
Piping questions often connect directly to Domain 3 material - a refrigerant piping question, for example, may test both proper installation practice and its effect on system performance. Treat these two domains as related rather than isolated study blocks.
Domain 3: Refrigeration and Air Conditioning
Refrigeration and Air Conditioning is the largest domain on the entire exam at 25 of 100 questions - a full quarter of your score. Any serious preparation plan has to treat this domain as the priority, and it's the section our MD-JHVACR Cheat Sheet 2026 devotes the most space to.
Refrigeration and Air Conditioning
This domain tests the refrigeration cycle itself along with the diagnostic and installation knowledge needed to service cooling equipment competently.
- Refrigeration cycle components: compressor, condenser, metering device, evaporator
- Superheat and subcooling calculations and their diagnostic use
- Refrigerant handling, recovery, and charging procedures
- Common AC system faults and the sequence for isolating them
Key Takeaway
Since Domain 3 carries 25% of the exam weight by itself, spend proportionally more review time here than on any other domain - including extra practice reading pressure-temperature relationships using your approved Modern Refrigeration and Air Conditioning reference.
Domain 4: Heating Systems
Heating Systems ties Electrical Knowledge as the second-largest domain, with 20 of 100 questions. This section covers combustion equipment, heat pumps, and the safety controls specific to heating appliances.
Heating Systems
Candidates need working knowledge of gas, oil, and electric heating equipment, plus the controls that keep each type operating safely.
- Gas furnace ignition systems, gas valves, and venting requirements
- Heat pump operation, including defrost cycles and reversing valves
- Combustion safety controls: flame sensors, limit switches, and rollout switches
- Sizing and load considerations referencing ACCA Manual J principles
Because Heating Systems and Refrigeration and Air Conditioning together account for 45 of the exam's 100 questions, these two domains alone determine nearly half your outcome. Candidates preparing with our practice materials on the main MD-JHVACR practice test platform will notice these two areas receive the heaviest question volume for exactly this reason.
Domain 5: Air Distribution Systems
Air Distribution Systems covers 15 of the 100 questions. This domain tests how air moves through a building once it leaves the equipment - ductwork, airflow balancing, and the tools used to measure and size distribution systems.
Air Distribution Systems
Expect questions on duct sizing, material selection, and airflow diagnostics rather than equipment-level repair.
- Duct sizing methods, including use of the ACCA Ductulator
- Sheet metal, flex duct, and fiberglass duct board applications
- Static pressure concepts and their impact on system performance
- Balancing dampers and airflow measurement basics
Since the Ductulator is one of the approved references you're permitted to bring, practice using the physical tool before test day rather than relying on memorized formulas - the exam expects you to apply it, not just recite duct-sizing rules.
Domain 6: Safety
Safety is the smallest domain, worth only 5 of 100 questions, but candidates shouldn't treat it as an afterthought. These questions draw directly from the listed OSHA 29 CFR 1926 reference and cover job-site hazards specific to HVACR trade work.
Safety
Focus on hazard recognition and correct procedure rather than broad general-industry safety rules.
- Refrigerant handling hazards and required personal protective equipment
- Electrical lockout/tagout procedures on HVACR equipment
- Confined space and ladder safety on job sites
- Proper handling and disposal of pressurized cylinders
With only five questions available, a missed point here has a smaller effect on your overall score than a missed point in Refrigeration and Air Conditioning - but Safety questions are typically straightforward if you've reviewed the reference material once.
Full Domain Allocation Table
Here is the complete official item allocation across all six domains, based on the Board-linked PSI bulletin:
| Domain | Content Area | Questions | Share of Exam |
|---|---|---|---|
| 1 | Electrical Knowledge, Motors, and Controls | 20 | 20% |
| 2 | Piping | 15 | 15% |
| 3 | Refrigeration and Air Conditioning | 25 | 25% |
| 4 | Heating Systems | 20 | 20% |
| 5 | Air Distribution Systems | 15 | 15% |
| 6 | Safety | 5 | 5% |
For context on how this allocation translates into an overall score requirement, see our breakdown of the MD-JHVACR Passing Score and how the 70% standard applies across all 100 questions combined rather than domain-by-domain.
Mapping a Study Timeline to the Blueprint
Rather than studying domains in numeric order, allocate time proportional to question weight. A candidate with several weeks before their PSI appointment might structure review like this:
Refrigeration and Air Conditioning
- Review the refrigeration cycle and pressure-temperature relationships
- Practice superheat/subcooling calculations using approved references
Heating Systems and Electrical
- Study gas and heat pump systems, ignition and safety controls
- Review motor types, control circuits, and basic circuit math
Piping and Air Distribution
- Practice duct sizing with the ACCA Ductulator
- Review pipe joining methods and condensate drain requirements
Safety and Full Review
- Read the OSHA 29 CFR 1926 reference sections relevant to HVACR
- Take full-length timed practice sessions covering all six domains
This weighting mirrors the actual blueprint - heaviest emphasis on Refrigeration and Air Conditioning, followed closely by Heating Systems and Electrical Knowledge, with Piping and Air Distribution next, and Safety reviewed but not over-studied. For a deeper explanation of pacing strategy across the full 240-minute window, see How Hard Is the MD-JHVACR Exam?.
Because this is the full HVACR Journeyman examination rather than the Journeyman Restricted version, all six domains apply to every candidate regardless of specialty background. If you're still confirming which exam track applies to your apprenticeship, review What Is MD-JHVACR? and MD-JHVACR Meaning for a plain-language explanation of the credential itself, or check MD-JHVACR Exam Dates 2026 before locking in a testing window around your domain review schedule.
Frequently Asked Questions
Refrigeration and Air Conditioning is the largest domain, with 25 of the exam's 100 questions - a quarter of your total score.
Safety is the smallest domain, worth only 5 of 100 questions, though it still requires familiarity with the OSHA 29 CFR 1926 reference.
Yes. Both domains are allocated 20 questions each on the official blueprint, tying for second-largest behind Refrigeration and Air Conditioning.
No. Handwritten reference notes, loose papers, and outside study guides are prohibited. Only advance highlighting and permanent tabs are allowed in the approved reference materials themselves.
The 70% passing standard applies to your combined score across all six domains. See our MD-JHVACR Pass Rate and MD-JHVACR Passing Score guides for a closer look at how that threshold works in practice.