NEVADA (NV) C-21B AIR-
CONDITIONING CONTRACTOR PRACTICE
EXAM 2026 — VERSION 2.0
150 ADVANCED QuESTIONS &
ANSwERS wITh DETAIlED
RATIONAlES | COMPlETE EXAM PREP
& STuDy GuIDE
TABLE OF CONTENTS
SECTION 1: ADVANCED THERMODYNAMICS & PSYCHROMETRICS (Questions 1–20)
• First, Second, and Third Laws of Thermodynamics
• Psychrometric Chart Interpretation
• Sensible, Latent, and Total Heat Calculations
• Refrigeration Cycle Analysis
• Superheat and Subcooling Mastery
SECTION 2: LOAD CALCULATIONS & SYSTEM DESIGN (Questions 21–35)
• Manual J, Manual N, Manual S, and Manual D Applications
• Commercial vs. Residential Load Determination
• Duct Design and Static Pressure
• Equipment Selection and Performance Curves
, • Zoning and Air Distribution
SECTION 3: COMPLEX SYSTEMS & EQUIPMENT (Questions 36–60)
• Split Systems, Packaged Units, and Rooftop Systems
• Heat Pumps, Geothermal, and Water-Source Systems
• Chillers, Cooling Towers, and Boilers
• VRF and Multi-Zone Systems
• Variable Speed and Inverter Technology
• System Integration and Controls
SECTION 4: ADVANCED ELECTRICAL & CONTROLS (Questions 61–80)
• NEC Article 440 and 430 Applications
• Motor Starting Circuits and Protection
• Variable Frequency Drives (VFDs)
• Building Automation Systems (BAS) and Protocols
• Advanced Troubleshooting and Diagnostics
• Electrical Safety and Lockout/Tagout
SECTION 5: REFRIGERANTS, PIPING & EPA COMPLIANCE (Questions 81–100)
• EPA Section 608 and AIM Act 2026 Updates
• Refrigerant Transition: R-410A, R-454B, R-32
• Piping Design, Oil Return, and Line Sizing
• Brazing, Flaring, and System Dehydration
• Leak Detection and Repair Requirements
• Refrigerant Recovery and Recycling
SECTION 6: CODES, SAFETY & OSHA (Questions 101–120)
• Uniform Mechanical Code (UMC) 2021/2024
• International Mechanical Code (IMC)
, • OSHA 29 CFR 1926 Subpart L and M
• Combustion Air and Venting
• Pressure Testing and System Commissioning
• Firestopping and Clearances
SECTION 7: NEVADA CONTRACTOR LAW & BUSINESS MANAGEMENT (Questions
121–135)
• NAC 624.380 Classification and Scope
• NRS 624 Licensing, Bonds, and Insurance
• Bid Limits and Contract Requirements
• Lien Law and Preliminary Notices
• Business Practices and Ethics
SECTION 8: COMPREHENSIVE SCENARIO-BASED QUESTIONS (Questions 136–150)
• Integrated System Design Scenarios
• Troubleshooting and Diagnostics
• Code Compliance and Safety Scenarios
• Contracting and Project Management
• Mixed-Domain Application Problems
SECTION 1: ADVANCED THERMODYNAMICS & PSYCHROMETRICS
Q1. According to the Second Law of Thermodynamics, which statement BEST describes the
behavior of heat in an air conditioning system?
A) Heat naturally flows from colder to warmer bodies without external work
B) Heat can be completely converted to work with 100% efficiency in a closed cycle
C) Heat will not flow spontaneously from a colder to a warmer body without external energy
input
D) The entropy of a perfect crystal at absolute zero is zero
, CORRECT ANSwER : C
Rationale: The Second Law states that heat cannot spontaneously flow from a colder body to
a warmer body without external work input. This is the fundamental principle underlying
mechanical refrigeration, where a compressor provides the work necessary to move heat from a
cold indoor space to a warmer outdoor environment. Option A describes the natural direction
(hot to cold). Option B violates the Second Law (Carnot efficiency limits). Option D describes the
Third Law.
Q2. On a psychrometric chart, what is the significance of the intersection where the dry-
bulb temperature line meets the saturation curve?
A) The point where relative humidity is 0%
B) The point where wet-bulb and dry-bulb temperatures are equal
C) The point where specific volume is maximized
D) The point where enthalpy is minimized
CORRECT ANSwER : B
Rationale: The saturation curve (100% relative humidity) on a psychrometric chart represents
the dew point. At any point on this curve, the dry-bulb temperature equals the wet-bulb
temperature, and the air is fully saturated with moisture. This is a critical concept for
understanding evaporative cooling and coil performance.
Q3. A technician measures the following conditions in a return air duct: dry-bulb
temperature of 75°F and wet-bulb temperature of 62°F. Using the psychrometric chart, what is
the approximate relative humidity?
A) 30%
B) 45%
C) 55%
D) 68%
CORRECT ANSwER : B
Rationale: Using the psychrometric chart, at 75°F dry-bulb and 62°F wet-bulb, the relative
humidity is approximately 45%. The wet-bulb depression (75 - 62 = 13°F) indicates moderate
CONDITIONING CONTRACTOR PRACTICE
EXAM 2026 — VERSION 2.0
150 ADVANCED QuESTIONS &
ANSwERS wITh DETAIlED
RATIONAlES | COMPlETE EXAM PREP
& STuDy GuIDE
TABLE OF CONTENTS
SECTION 1: ADVANCED THERMODYNAMICS & PSYCHROMETRICS (Questions 1–20)
• First, Second, and Third Laws of Thermodynamics
• Psychrometric Chart Interpretation
• Sensible, Latent, and Total Heat Calculations
• Refrigeration Cycle Analysis
• Superheat and Subcooling Mastery
SECTION 2: LOAD CALCULATIONS & SYSTEM DESIGN (Questions 21–35)
• Manual J, Manual N, Manual S, and Manual D Applications
• Commercial vs. Residential Load Determination
• Duct Design and Static Pressure
• Equipment Selection and Performance Curves
, • Zoning and Air Distribution
SECTION 3: COMPLEX SYSTEMS & EQUIPMENT (Questions 36–60)
• Split Systems, Packaged Units, and Rooftop Systems
• Heat Pumps, Geothermal, and Water-Source Systems
• Chillers, Cooling Towers, and Boilers
• VRF and Multi-Zone Systems
• Variable Speed and Inverter Technology
• System Integration and Controls
SECTION 4: ADVANCED ELECTRICAL & CONTROLS (Questions 61–80)
• NEC Article 440 and 430 Applications
• Motor Starting Circuits and Protection
• Variable Frequency Drives (VFDs)
• Building Automation Systems (BAS) and Protocols
• Advanced Troubleshooting and Diagnostics
• Electrical Safety and Lockout/Tagout
SECTION 5: REFRIGERANTS, PIPING & EPA COMPLIANCE (Questions 81–100)
• EPA Section 608 and AIM Act 2026 Updates
• Refrigerant Transition: R-410A, R-454B, R-32
• Piping Design, Oil Return, and Line Sizing
• Brazing, Flaring, and System Dehydration
• Leak Detection and Repair Requirements
• Refrigerant Recovery and Recycling
SECTION 6: CODES, SAFETY & OSHA (Questions 101–120)
• Uniform Mechanical Code (UMC) 2021/2024
• International Mechanical Code (IMC)
, • OSHA 29 CFR 1926 Subpart L and M
• Combustion Air and Venting
• Pressure Testing and System Commissioning
• Firestopping and Clearances
SECTION 7: NEVADA CONTRACTOR LAW & BUSINESS MANAGEMENT (Questions
121–135)
• NAC 624.380 Classification and Scope
• NRS 624 Licensing, Bonds, and Insurance
• Bid Limits and Contract Requirements
• Lien Law and Preliminary Notices
• Business Practices and Ethics
SECTION 8: COMPREHENSIVE SCENARIO-BASED QUESTIONS (Questions 136–150)
• Integrated System Design Scenarios
• Troubleshooting and Diagnostics
• Code Compliance and Safety Scenarios
• Contracting and Project Management
• Mixed-Domain Application Problems
SECTION 1: ADVANCED THERMODYNAMICS & PSYCHROMETRICS
Q1. According to the Second Law of Thermodynamics, which statement BEST describes the
behavior of heat in an air conditioning system?
A) Heat naturally flows from colder to warmer bodies without external work
B) Heat can be completely converted to work with 100% efficiency in a closed cycle
C) Heat will not flow spontaneously from a colder to a warmer body without external energy
input
D) The entropy of a perfect crystal at absolute zero is zero
, CORRECT ANSwER : C
Rationale: The Second Law states that heat cannot spontaneously flow from a colder body to
a warmer body without external work input. This is the fundamental principle underlying
mechanical refrigeration, where a compressor provides the work necessary to move heat from a
cold indoor space to a warmer outdoor environment. Option A describes the natural direction
(hot to cold). Option B violates the Second Law (Carnot efficiency limits). Option D describes the
Third Law.
Q2. On a psychrometric chart, what is the significance of the intersection where the dry-
bulb temperature line meets the saturation curve?
A) The point where relative humidity is 0%
B) The point where wet-bulb and dry-bulb temperatures are equal
C) The point where specific volume is maximized
D) The point where enthalpy is minimized
CORRECT ANSwER : B
Rationale: The saturation curve (100% relative humidity) on a psychrometric chart represents
the dew point. At any point on this curve, the dry-bulb temperature equals the wet-bulb
temperature, and the air is fully saturated with moisture. This is a critical concept for
understanding evaporative cooling and coil performance.
Q3. A technician measures the following conditions in a return air duct: dry-bulb
temperature of 75°F and wet-bulb temperature of 62°F. Using the psychrometric chart, what is
the approximate relative humidity?
A) 30%
B) 45%
C) 55%
D) 68%
CORRECT ANSwER : B
Rationale: Using the psychrometric chart, at 75°F dry-bulb and 62°F wet-bulb, the relative
humidity is approximately 45%. The wet-bulb depression (75 - 62 = 13°F) indicates moderate
