Nevada C-21B Air Conditioning Contractor
Practice Exam 300 Questions with Correct
Answers and Explanations in Italic.
EXAM OVERVIEW
Category Details
License Type C-21B Air Conditioning Contractor
Governing Body Nevada State Contractors Board (NSCB)
Legal Authority NRS 624 (Nevada Revised Statutes)
Experience Required 4 years in the trade
Exams Required Trade-specific (C-21B) + Business and Law (Contractor Management Survey)
SECTION 1: FUNDAMENTALS OF AIR CONDITIONING
Question 1: Which of the following best describes the primary function of an air
conditioning system as defined for a C-21B contractor in Nevada?
A) To provide complete building automation
B) To regulate indoor temperature and humidity
C) To serve as a primary heating source
D) To replace mechanical ventilation systems
Correct Answer: B) To regulate indoor temperature and humidity
Explanation: Under NAC 624.380, the C-21B subclassification specifically covers
equipment that uses evaporation, refrigeration, boilers, or combustion for the control of air
temperatures, including humidity controls .
,Question 2: What is the primary difference between sensible heat and latent heat in
HVAC calculations?
A) Sensible heat changes temperature, latent heat changes phase
B) Sensible heat changes pressure, latent heat changes volume
C) Sensible heat is measured in BTU/hr, latent heat in kW
D) Sensible heat is only in cooling, latent heat only in heating
Correct Answer: A) Sensible heat changes temperature, latent heat changes phase
Explanation: Sensible heat results in a temperature change without a phase change,
while latent heat involves a phase change (e.g., condensation or evaporation) at constant
temperature .
Question 3: What is the term for heat that changes the temperature of a substance
without changing its physical state?
A) Latent heat
B) Superheat
C) Subcooling
D) Sensible heat
Correct Answer: D) Sensible heat
Explanation: Sensible heat is the energy added or removed that causes a change in
temperature. Latent heat causes a phase change (melting, boiling) without a temperature
change .
Question 4: Which psychrometric property is directly read from the horizontal axis of a
psychrometric chart?
A) Relative humidity
B) Specific humidity
,C) Dry-bulb temperature
D) Enthalpy
Correct Answer: C) Dry-bulb temperature
Explanation: The horizontal axis of a psychrometric chart represents dry-bulb
temperature; other properties are plotted relative to this axis .
Question 5: In the refrigeration cycle, the evaporator operates at which of the following
conditions?
A) High pressure, high temperature
B) Low pressure, low temperature
C) High pressure, low temperature
D) Low pressure, high temperature
Correct Answer: B) Low pressure, low temperature
Explanation: The evaporator is the low-pressure, low-temperature side where refrigerant
absorbs heat and vaporizes .
Question 6: What is "latent heat" in the context of HVAC systems?
A) Heat that can be felt on a thermometer
B) Heat required to change the state of a substance without changing temperature
C) Heat generated by friction in the compressor
D) Heat lost through ductwork
Correct Answer: B) Heat required to change the state of a substance without
changing temperature
Explanation: Latent heat is "hidden" heat. In HVAC, it is the energy required to evaporate
water (condensate) or refrigerant, contributing to humidity control. Sensible heat changes
temperature .
, Question 7: Which component is primarily responsible for reducing the pressure of the
refrigerant before it enters the evaporator?
A) Compressor
B) Condenser
C) Expansion device
D) Receiver
Correct Answer: C) Expansion device
Explanation: The expansion device (thermal expansion valve, capillary tube, or fixed
orifice) creates a pressure drop, allowing the refrigerant to evaporate at low pressure in
the evaporator .
Question 8: What does an "A1" refrigerant classification signify according to ASHRAE?
A) Low toxicity, high flammability
B) Low toxicity, non-flammable
C) High toxicity, non-flammable
D) High toxicity, high flammability
Correct Answer: B) Low toxicity, non-flammable
Explanation: ASHRAE "A1" denotes refrigerants that are mildly toxic (Class A) and non-
flammable (Class 1), such as R-410A .
Question 9: Which refrigerant is commonly used in modern residential air conditioning
systems?
A) R-22
B) R-410A
C) R-12
D) Ammonia
Correct Answer: B) R-410A
Practice Exam 300 Questions with Correct
Answers and Explanations in Italic.
EXAM OVERVIEW
Category Details
License Type C-21B Air Conditioning Contractor
Governing Body Nevada State Contractors Board (NSCB)
Legal Authority NRS 624 (Nevada Revised Statutes)
Experience Required 4 years in the trade
Exams Required Trade-specific (C-21B) + Business and Law (Contractor Management Survey)
SECTION 1: FUNDAMENTALS OF AIR CONDITIONING
Question 1: Which of the following best describes the primary function of an air
conditioning system as defined for a C-21B contractor in Nevada?
A) To provide complete building automation
B) To regulate indoor temperature and humidity
C) To serve as a primary heating source
D) To replace mechanical ventilation systems
Correct Answer: B) To regulate indoor temperature and humidity
Explanation: Under NAC 624.380, the C-21B subclassification specifically covers
equipment that uses evaporation, refrigeration, boilers, or combustion for the control of air
temperatures, including humidity controls .
,Question 2: What is the primary difference between sensible heat and latent heat in
HVAC calculations?
A) Sensible heat changes temperature, latent heat changes phase
B) Sensible heat changes pressure, latent heat changes volume
C) Sensible heat is measured in BTU/hr, latent heat in kW
D) Sensible heat is only in cooling, latent heat only in heating
Correct Answer: A) Sensible heat changes temperature, latent heat changes phase
Explanation: Sensible heat results in a temperature change without a phase change,
while latent heat involves a phase change (e.g., condensation or evaporation) at constant
temperature .
Question 3: What is the term for heat that changes the temperature of a substance
without changing its physical state?
A) Latent heat
B) Superheat
C) Subcooling
D) Sensible heat
Correct Answer: D) Sensible heat
Explanation: Sensible heat is the energy added or removed that causes a change in
temperature. Latent heat causes a phase change (melting, boiling) without a temperature
change .
Question 4: Which psychrometric property is directly read from the horizontal axis of a
psychrometric chart?
A) Relative humidity
B) Specific humidity
,C) Dry-bulb temperature
D) Enthalpy
Correct Answer: C) Dry-bulb temperature
Explanation: The horizontal axis of a psychrometric chart represents dry-bulb
temperature; other properties are plotted relative to this axis .
Question 5: In the refrigeration cycle, the evaporator operates at which of the following
conditions?
A) High pressure, high temperature
B) Low pressure, low temperature
C) High pressure, low temperature
D) Low pressure, high temperature
Correct Answer: B) Low pressure, low temperature
Explanation: The evaporator is the low-pressure, low-temperature side where refrigerant
absorbs heat and vaporizes .
Question 6: What is "latent heat" in the context of HVAC systems?
A) Heat that can be felt on a thermometer
B) Heat required to change the state of a substance without changing temperature
C) Heat generated by friction in the compressor
D) Heat lost through ductwork
Correct Answer: B) Heat required to change the state of a substance without
changing temperature
Explanation: Latent heat is "hidden" heat. In HVAC, it is the energy required to evaporate
water (condensate) or refrigerant, contributing to humidity control. Sensible heat changes
temperature .
, Question 7: Which component is primarily responsible for reducing the pressure of the
refrigerant before it enters the evaporator?
A) Compressor
B) Condenser
C) Expansion device
D) Receiver
Correct Answer: C) Expansion device
Explanation: The expansion device (thermal expansion valve, capillary tube, or fixed
orifice) creates a pressure drop, allowing the refrigerant to evaporate at low pressure in
the evaporator .
Question 8: What does an "A1" refrigerant classification signify according to ASHRAE?
A) Low toxicity, high flammability
B) Low toxicity, non-flammable
C) High toxicity, non-flammable
D) High toxicity, high flammability
Correct Answer: B) Low toxicity, non-flammable
Explanation: ASHRAE "A1" denotes refrigerants that are mildly toxic (Class A) and non-
flammable (Class 1), such as R-410A .
Question 9: Which refrigerant is commonly used in modern residential air conditioning
systems?
A) R-22
B) R-410A
C) R-12
D) Ammonia
Correct Answer: B) R-410A
