Nevada Refrigeration and Air Conditioning Contractor (C-21D) Exam Book Package

Prepare for the Nevada Refrigeration and Air Conditioning Contractor (C-21D) examination with a focused exam book package built around refrigeration and air-conditioning maintenance, troubleshooting, mechanical code requirements, system components, repair practices, and construction safety. This package combines the Uniform Mechanical Code, 2018, which is allowed into the open-book examination, with supplemental study references used to strengthen technical knowledge before test day.

The Nevada C-21D examination is an open-book test. The Uniform Mechanical Code, 2018 is the exam-room-approved reference included with this package. Troubleshooting and Servicing Modern Air Conditioning and Refrigeration Systems, Modern Refrigeration and Air Conditioning, 22nd edition, and Code of Federal Regulations - 29 CFR Part 1926 (OSHA) are included for preparation but are not allowed into the examination room.

The C-21D trade examination contains 60 questions, allows 2 hours for completion, and requires 42 correct answers to pass. Because the classification centers on maintaining and repairing existing refrigeration and air-conditioning systems, candidates should develop strong working knowledge of system diagnostics, compressors, motors, relays, coils, heat exchangers, refrigeration cycles, controls, equipment operation, and safe service procedures.

Nevada identifies C-21D as the Maintenance subclassification under Refrigeration and Air-Conditioning. The classification covers repair and replacement of parts of existing air-conditioning and refrigeration units or systems, including compressors, motors, relays, coils, heat exchangers, and related equipment. The scope does not include replacement of complete condenser assemblies on remote systems, air handlers, or work that alters the design of an existing system.

This distinction makes C-21D especially focused on service and maintenance rather than complete system redesign or major system replacement. Candidates should be able to recognize system problems, understand the function of individual components, interpret operating conditions, identify likely causes of failure, and determine appropriate maintenance or repair procedures.

The package is useful for candidates who want both the code reference permitted during the examination and additional technical books for building the knowledge needed to answer service, troubleshooting, refrigeration, air-conditioning, and safety questions without relying on code lookups alone.

What You Get

• Uniform Mechanical Code, 2018 — exam-room-approved reference supporting refrigeration systems, air-conditioning equipment, mechanical installation requirements, ventilation, piping, equipment rooms, safety provisions, and related code topics.
• Troubleshooting and Servicing Modern Air Conditioning and Refrigeration Systems — study-only reference focused on system diagnosis, troubleshooting procedures, servicing techniques, component testing, operating conditions, and repair practices.
• Modern Refrigeration and Air Conditioning, 22nd edition — study-only technical reference covering refrigeration cycles, refrigerants, compressors, condensers, evaporators, controls, electrical components, air conditioning, service procedures, and equipment operation.
• Code of Federal Regulations - 29 CFR Part 1926 (OSHA) — study-only reference supporting preparation for construction safety, personal protective equipment, ladders, tools, electrical hazards, material handling, and general jobsite safety.
• Open-Book Exam Preparation: Use the Uniform Mechanical Code throughout your studies to improve reference-navigation speed before test day.
• Maintenance-Focused Study: Build knowledge around repair, component replacement, diagnostics, service procedures, and existing-system maintenance.

Exam Details

The Nevada C-21D Refrigeration and Air Conditioning Maintenance Contractor examination contains 60 questions. Candidates are allowed 2 hours to complete the examination and must answer 42 questions correctly to pass.

The exam is designed around the knowledge required to maintain and repair existing refrigeration and air-conditioning systems. Preparation should include refrigeration principles, troubleshooting, mechanical equipment, controls, electrical components, piping, ventilation, system testing, equipment service, and safety.

Candidates should be comfortable with the basic refrigeration cycle and the way major components interact. A service technician must be able to recognize whether a problem is related to the compressor, condenser, evaporator, metering device, airflow, controls, electrical components, refrigerant circuit, or another part of the system.

Troubleshooting skills are particularly important for the C-21D classification. Candidates should understand how symptoms such as insufficient cooling, high or low pressures, compressor problems, poor airflow, icing, electrical failures, and control malfunctions can point toward different causes.

Because the examination allows two hours for 60 questions, candidates have an average of approximately two minutes per question. Efficient preparation should therefore combine strong technical knowledge with fast use of the approved mechanical code.

Open Book Test

The Nevada C-21D Refrigeration and Air Conditioning Contractor examination is an open-book test.

The following reference included in this package is allowed into the examination:

• Uniform Mechanical Code, 2018

The following books are included for study but are not allowed into the examination room:

• Troubleshooting and Servicing Modern Air Conditioning and Refrigeration Systems
• Modern Refrigeration and Air Conditioning, 22nd edition
• Code of Federal Regulations - 29 CFR Part 1926 (OSHA)

The Uniform Mechanical Code should be used throughout preparation so candidates become familiar with refrigeration and mechanical requirements before exam day. Practice locating sections related to refrigeration equipment, machinery rooms, piping, ventilation, ducts, mechanical systems, equipment installation, and safety.

Open-book testing does not mean candidates should search the code for every answer. Many C-21D questions involve troubleshooting and service knowledge that should be understood from experience and preparation. The code is most useful when a specific requirement, definition, installation condition, clearance, equipment rule, or mechanical provision needs to be located.

Timed code-navigation practice can help candidates decide whether a lookup is worth the time. Start with a subject, identify the likely UMC chapter, locate the provision, and return to the question. Repeating this process before test day can make the open-book format much more useful.

Licensing Steps

1. Confirm the C-21D classification. Make sure Refrigeration and Air Conditioning Maintenance matches the type of work the business intends to perform.
2. Identify the qualifying individual. The contractor application must identify the person responsible for meeting the applicable trade qualification requirements.
3. Document qualifying experience. Prepare work-history information demonstrating experience related to refrigeration and air-conditioning maintenance and repair.
4. Submit the Nevada contractor license application. Complete the applicable application and supporting documentation.
5. Receive examination eligibility. After the application and qualification information are reviewed, the qualifying individual can proceed with the required examinations.
6. Prepare for the C-21D trade examination. Study refrigeration systems, air-conditioning equipment, troubleshooting, controls, service procedures, mechanical code requirements, and safety.
7. Practice UMC navigation. Use the Uniform Mechanical Code during preparation so applicable code provisions can be located efficiently.
8. Prepare for Nevada Business and Law. Contractor applicants must satisfy the applicable Nevada business and law requirement unless an authorized waiver applies.
9. Complete the required examinations. Take the applicable trade and business examinations.
10. Complete remaining licensing requirements. Finish the additional state requirements associated with contractor license issuance.

State Requirements

Nevada recognizes C-21D Maintenance as a subclassification under C-21 Refrigeration and Air-Conditioning.

The classification authorizes the repair and replacement of parts of existing air-conditioning and refrigeration units or systems, including compressors, motors, relays, coils, heat exchangers, and other associated equipment.

The scope is specifically directed toward maintaining and repairing existing systems. It does not authorize replacement of complete condenser assemblies on remote systems, replacement of air handlers, or work that alters the design of an existing system.

This makes C-21D different from a broader installation classification. Candidates should prepare for service-oriented work such as diagnostics, maintenance, repair, component replacement, system testing, and recognition of operating problems rather than full HVAC system redesign.

Understanding the limits of the classification is important. A maintenance contractor may work extensively within an existing system while still being restricted from performing work that changes the original system design or replaces certain major assemblies.

The C-21D examination is only one part of Nevada contractor licensing. Applicants must also satisfy the applicable qualification, application, business and law, and other licensing requirements before a contractor license is issued.

Reference Books

• Uniform Mechanical Code, 2018
  This exam-room-approved reference supports preparation involving refrigeration systems, mechanical equipment, piping, ventilation, equipment rooms, installation requirements, and mechanical code provisions relevant to refrigeration and air-conditioning maintenance work.
• Troubleshooting and Servicing Modern Air Conditioning and Refrigeration Systems
  This study-only reference supports preparation involving system diagnosis, troubleshooting sequences, refrigeration and air-conditioning service procedures, component testing, operating conditions, electrical checks, and practical repair techniques. This book is not allowed into the examination.
• Modern Refrigeration and Air Conditioning, 22nd edition
  This study-only reference supports refrigeration theory, refrigerants, compressors, condensers, evaporators, metering devices, controls, electrical components, airflow, air-conditioning systems, maintenance, and troubleshooting. This book is not allowed into the examination.
• Code of Federal Regulations - 29 CFR Part 1926 (OSHA)
  This study-only reference supports construction safety preparation involving personal protective equipment, electrical hazards, ladders, tools, fall hazards, material handling, and general safe work practices. This book is not allowed into the examination.

Exam Room Approved Books

• Uniform Mechanical Code, 2018
  This is the exam-room-approved reference included with the Nevada C-21D Refrigeration and Air Conditioning Contractor Exam Book Package. Candidates should use it throughout preparation to become familiar with mechanical, refrigeration, ventilation, equipment, piping, and applicable code requirements.

Test Information and Study Materials

A productive Nevada C-21D study plan should focus heavily on troubleshooting and maintenance. The classification is built around repairing and replacing components in existing systems, so candidates should be able to evaluate symptoms and connect them to likely equipment or system problems.

The Refrigeration Cycle should be one of the first areas reviewed. Candidates should understand compression, condensation, expansion, and evaporation and how pressure, temperature, and refrigerant condition change throughout the cycle.

Compressors are central to refrigeration and air-conditioning systems. Review compressor function, operating conditions, electrical components, lubrication concepts, overheating, abnormal pressures, and common causes of compressor failure.

Condensers should be studied in relation to heat rejection, airflow, coil condition, fan operation, ambient temperature, and pressure. Candidates should understand how restricted airflow or dirty surfaces can affect system performance.

Evaporators should be reviewed in relation to heat absorption, airflow, coil temperature, refrigerant condition, icing, and drainage. Problems in the evaporator section can produce symptoms that resemble refrigerant or airflow issues.

Metering Devices should be studied according to their role in controlling refrigerant flow and creating the pressure difference needed for the refrigeration cycle. Candidates should understand how improper operation can affect superheat, evaporator performance, and system pressures.

Refrigerant System Troubleshooting should include recognition of abnormal high-side and low-side pressures, undercharge, overcharge, airflow restrictions, refrigerant restrictions, contamination, and component problems.

Controls and Electrical Components are another major part of maintenance work. Candidates should review relays, contactors, thermostats, capacitors, motors, pressure switches, transformers, safety controls, and basic control circuits.

A technician should understand how to separate an electrical failure from a refrigeration-system failure. A compressor that does not run, for example, can result from control issues, electrical problems, safety-device operation, or compressor failure.

Motors and Blowers should be studied in relation to airflow, electrical operation, rotation, bearings, capacitors, speed, and mechanical condition. Poor airflow can affect both comfort and refrigeration-system pressures.

Heat Exchangers and heating components should be reviewed where they are part of existing HVAC systems. Candidates should understand basic operating principles, inspection concerns, airflow effects, and maintenance considerations.

Piping and Tubing should include refrigerant line function, fittings, supports, insulation, leaks, restrictions, and proper service practices. The condition of piping can affect pressure drop, refrigerant flow, oil return, and overall system performance.

System Testing should include pressure and temperature evaluation, electrical measurements, airflow observations, leak detection concepts, and the process of comparing actual system behavior with expected operation.

Preventive Maintenance should be considered alongside repair work. Cleaning coils, checking filters, inspecting electrical connections, evaluating motors, examining condensate systems, and monitoring system operation can help identify issues before larger failures occur.

The Troubleshooting and Servicing Modern Air Conditioning and Refrigeration Systems reference should be used to develop a systematic diagnostic approach. Instead of replacing components based only on symptoms, candidates should practice confirming the cause of a problem through observation and testing.

The Modern Refrigeration and Air Conditioning, 22nd edition provides the technical foundation needed to understand why a system behaves the way it does. Candidates should connect theory to service work so pressure, temperature, airflow, and electrical readings have practical meaning.

Safety must also be part of preparation. Refrigeration and air-conditioning maintenance may involve electrical circuits, pressurized refrigerant systems, ladders, tools, moving machinery, hot surfaces, sharp sheet metal, and elevated work locations.

Because the OSHA reference is not allowed in the examination, candidates should move from reading to active recall. Review a safety topic, close the book, and practice explaining the correct procedure without looking at the text.

The Uniform Mechanical Code, 2018 should be handled differently because it is permitted during the exam. Practice using the table of contents, index, definitions, refrigeration chapters, equipment provisions, and ventilation sections under timed conditions.

A useful study method is to work through troubleshooting questions without the technical books nearby, then use the UMC only when the question requires a specific mechanical code provision. This better reflects the balance between retained technical knowledge and open-book navigation.

Time management should also be practiced. With 60 questions in two hours, candidates should avoid spending several minutes searching for one answer. If a lookup becomes difficult, continue with the exam and return later when possible.

How 1 Exam Prep Helps You Reach Your Goal

1 Exam Prep supports Nevada C-21D Refrigeration and Air Conditioning Maintenance Contractor candidates through organized study guidance, trade-focused review, practice-oriented preparation, reference navigation, and confidence-building study structure.

The C-21D exam is centered on real maintenance and repair knowledge. 1 Exam Prep helps candidates organize preparation around refrigeration systems, troubleshooting, controls, electrical components, airflow, mechanical code requirements, service procedures, and safety.

The Uniform Mechanical Code, 2018 can be used throughout preparation to build familiarity with the same reference available during the open-book examination. Repeated code-navigation drills can help candidates locate requirements more efficiently when time matters.

The troubleshooting and refrigeration references provide deeper technical study for questions that must be answered from retained knowledge. Candidates can use them to strengthen understanding of system operation, failure symptoms, diagnostic procedures, and equipment service.

Practice-oriented preparation can help identify whether a missed question comes from a technical knowledge gap, weak troubleshooting logic, difficulty locating a code requirement, or poor time management. Focusing on the cause of the mistake can make each study session more productive.

The goal is to help candidates approach the Nevada C-21D Refrigeration and Air Conditioning Maintenance Contractor examination with stronger service knowledge, better troubleshooting skills, more efficient UMC navigation, and a structured preparation strategy without guaranteeing a passing score or licensing approval.

How many questions are on the Nevada C-21D exam?

The Nevada C-21D Refrigeration and Air Conditioning Maintenance Contractor examination contains 60 questions.

How much time is allowed for the C-21D examination?

Candidates are allowed 2 hours to complete the examination.

How many correct answers are required to pass?

Candidates must answer 42 questions correctly to pass the C-21D trade examination.

Is the Nevada C-21D exam open book?

Yes. The Nevada C-21D Refrigeration and Air Conditioning Maintenance Contractor examination is an open-book test.

Which book is allowed into the C-21D exam?

The Uniform Mechanical Code, 2018 is the exam-room-approved reference included with this package.

Is Troubleshooting and Servicing Modern Air Conditioning and Refrigeration Systems allowed into the exam?

No. It is included for technical study and troubleshooting preparation but is not allowed into the examination.

Is Modern Refrigeration and Air Conditioning allowed into the exam?

No. Modern Refrigeration and Air Conditioning, 22nd edition is a study-only reference and is not allowed into the examination.

Is OSHA 29 CFR Part 1926 allowed into the C-21D exam?

No. OSHA 29 CFR Part 1926 is included for safety preparation but is not allowed into the examination.

What work does the Nevada C-21D classification cover?

The C-21D classification covers repair and replacement of parts of existing refrigeration and air-conditioning systems, including compressors, motors, relays, coils, heat exchangers, and related equipment.

Can a C-21D contractor alter the design of an existing system?

No. The C-21D maintenance scope does not include work that alters the design of an existing refrigeration or air-conditioning system.

Can a C-21D contractor replace complete condenser assemblies on remote systems?

No. Replacement of complete condenser assemblies on remote systems is outside the C-21D maintenance scope.

Does the C-21D scope include compressor replacement?

Yes. The maintenance classification includes repair and replacement of parts such as compressors within existing systems.

What should I focus on while studying?

Focus on refrigeration fundamentals, troubleshooting, compressors, motors, controls, coils, heat exchangers, airflow, service procedures, mechanical code requirements, and safety.

How should I use the Uniform Mechanical Code while preparing?

Practice targeted lookups using the table of contents, index, definitions, refrigeration sections, equipment provisions, and other relevant mechanical chapters under timed conditions.

Should I try to look up every answer during the exam?

No. Build strong troubleshooting and refrigeration knowledge first and use the Uniform Mechanical Code strategically when a specific code requirement, definition, or mechanical provision needs to be confirmed.

Does this package guarantee that I will pass the Nevada C-21D exam?

No. This package provides exam and study references designed to support organized preparation. Examination results depend on each candidate's experience, technical knowledge, study, troubleshooting ability, code-navigation skills, and performance on test day.