NEVADA C-21B AIR-CONDITIONING CONTRACTOR
EXAMINATION COMPLETE QUESTIONS AND DETAILED
SOLUTIONS LATEST UPDATE THIS YEAR JUST RELEASED
1. What is the primary purpose of an evaporator in a conventional
vapor-compression air-conditioning system?
A. Reject heat into outdoor air
B. Absorb heat from the conditioned space
C. Increase refrigerant pressure
D. Store liquid refrigerant
Answer: B
Rationale: The evaporator absorbs heat from indoor air as refrigerant
changes from liquid to vapor, thereby producing the desired cooling
effect.
2. Which component normally raises refrigerant vapor from
evaporator pressure to condenser pressure?
A. Expansion valve
B. Filter-drier
C. Compressor
D. Receiver
Answer: C
,Rationale: The compressor increases refrigerant vapor pressure and
temperature while moving refrigerant through the refrigeration cycle
toward the condenser.
3. What occurs when refrigerant passes through a properly operating
metering device?
A. Pressure increases substantially
B. Pressure drops and refrigerant begins evaporating
C. Vapor becomes completely superheated immediately
D. Condenser pressure increases
Answer: B
Rationale: The metering device creates a pressure drop that allows
high-pressure liquid refrigerant to enter the lower-pressure evaporator.
4. What is sensible heat?
A. Heat associated with a phase change
B. Heat that changes temperature without changing physical state
C. Heat produced exclusively by combustion
D. Heat contained only in refrigerant
Answer: B
Rationale: Sensible heat changes the measurable temperature of a
substance without causing a change between solid, liquid, or vapor
states.
,5. What is latent heat primarily associated with?
A. Temperature measurement
B. Phase change
C. Electrical resistance
D. Air velocity
Answer: B
Rationale: Latent heat is energy absorbed or released during a phase
change while the substance's temperature remains essentially
constant.
6. What generally happens to refrigerant saturation temperature
when pressure increases?
A. It decreases
B. It remains unchanged
C. It increases
D. It becomes impossible to determine
Answer: C
Rationale: For a given refrigerant, higher saturation pressure
corresponds to higher saturation temperature according to its
pressure-temperature relationship.
7. Why is superheat measured at the evaporator outlet or suction
line?
, A. To determine condenser capacity
B. To verify that liquid refrigerant is not entering the compressor
C. To measure indoor humidity directly
D. To calculate duct friction
Answer: B
Rationale: Adequate suction superheat helps confirm that refrigerant
leaving the evaporator is vapor rather than potentially damaging liquid
entering the compressor.
8. What does subcooling describe in a refrigeration system?
A. Vapor above its saturation temperature
B. Liquid below its saturation temperature
C. Air below freezing
D. Refrigerant above critical pressure
Answer: B
Rationale: Subcooling occurs when liquid refrigerant is cooled below its
saturation temperature at the measured condensing pressure.
9. A dirty condenser coil will commonly cause which condition?
A. Lower head pressure
B. Higher condensing pressure
C. Lower compressor discharge temperature
D. Excessive evaporator airflow
Answer: B
EXAMINATION COMPLETE QUESTIONS AND DETAILED
SOLUTIONS LATEST UPDATE THIS YEAR JUST RELEASED
1. What is the primary purpose of an evaporator in a conventional
vapor-compression air-conditioning system?
A. Reject heat into outdoor air
B. Absorb heat from the conditioned space
C. Increase refrigerant pressure
D. Store liquid refrigerant
Answer: B
Rationale: The evaporator absorbs heat from indoor air as refrigerant
changes from liquid to vapor, thereby producing the desired cooling
effect.
2. Which component normally raises refrigerant vapor from
evaporator pressure to condenser pressure?
A. Expansion valve
B. Filter-drier
C. Compressor
D. Receiver
Answer: C
,Rationale: The compressor increases refrigerant vapor pressure and
temperature while moving refrigerant through the refrigeration cycle
toward the condenser.
3. What occurs when refrigerant passes through a properly operating
metering device?
A. Pressure increases substantially
B. Pressure drops and refrigerant begins evaporating
C. Vapor becomes completely superheated immediately
D. Condenser pressure increases
Answer: B
Rationale: The metering device creates a pressure drop that allows
high-pressure liquid refrigerant to enter the lower-pressure evaporator.
4. What is sensible heat?
A. Heat associated with a phase change
B. Heat that changes temperature without changing physical state
C. Heat produced exclusively by combustion
D. Heat contained only in refrigerant
Answer: B
Rationale: Sensible heat changes the measurable temperature of a
substance without causing a change between solid, liquid, or vapor
states.
,5. What is latent heat primarily associated with?
A. Temperature measurement
B. Phase change
C. Electrical resistance
D. Air velocity
Answer: B
Rationale: Latent heat is energy absorbed or released during a phase
change while the substance's temperature remains essentially
constant.
6. What generally happens to refrigerant saturation temperature
when pressure increases?
A. It decreases
B. It remains unchanged
C. It increases
D. It becomes impossible to determine
Answer: C
Rationale: For a given refrigerant, higher saturation pressure
corresponds to higher saturation temperature according to its
pressure-temperature relationship.
7. Why is superheat measured at the evaporator outlet or suction
line?
, A. To determine condenser capacity
B. To verify that liquid refrigerant is not entering the compressor
C. To measure indoor humidity directly
D. To calculate duct friction
Answer: B
Rationale: Adequate suction superheat helps confirm that refrigerant
leaving the evaporator is vapor rather than potentially damaging liquid
entering the compressor.
8. What does subcooling describe in a refrigeration system?
A. Vapor above its saturation temperature
B. Liquid below its saturation temperature
C. Air below freezing
D. Refrigerant above critical pressure
Answer: B
Rationale: Subcooling occurs when liquid refrigerant is cooled below its
saturation temperature at the measured condensing pressure.
9. A dirty condenser coil will commonly cause which condition?
A. Lower head pressure
B. Higher condensing pressure
C. Lower compressor discharge temperature
D. Excessive evaporator airflow
Answer: B
