NEVADA C-20 COMMERCIAL
REFRIGERATION PRACTICE EXAM
QUESTIONS AND VERIFIED ANSWERS
JUST RELEASED.
1. In a commercial refrigeration system using a Thermostatic Expansion Valve (TXV), what is
the primary purpose of the external equalizer line?
A. To bypass liquid refrigerant directly into the suction line.
B. To balance the pressure between the high side and low side during the off-cycle.
C. To increase the superheat setting for better compressor protection.
D. To compensate for the pressure drop across the evaporator coil.
Answer: D
Conceptual Explanation: An external equalizer line is used when there is a significant
pressure drop across the evaporator. It allows the TXV to sense the pressure at the
evaporator outlet rather than the inlet, ensuring accurate superheat control.
2. Which of the following describes the ‘Net Refrigeration Effect’ (NRE)?
A. The difference in enthalpy between the refrigerant entering the evaporator and leaving
the evaporator.
B. The total heat rejected by the condenser.
,C. The ratio of the heat of compression to the evaporator load.
D. The total energy consumed by the compressor motor in BTUs.
Answer: A
Conceptual Explanation: NRE is the amount of heat absorbed by each pound of
refrigerant as it passes through the evaporator, calculated as the difference in enthalpy
(Btu/lb) between the evaporator inlet and outlet.
3. When installing a walk-in freezer, why must the drain line be wrapped with heat tape and
insulated?
A. To prevent the condensate from boiling inside the pipe.
B. To maintain the temperature of the walk-in box.
C. To increase the efficiency of the defrost cycle.
D. To prevent the condensate water from freezing and clogging the line.
Answer: D
Conceptual Explanation: In low-temperature applications (freezers), condensate water
will freeze inside the drain line because the ambient temperature of the room is below
freezing. Heat tape prevents ice buildup.
4. What is the function of a Crankcase Pressure Regulator (CPR) valve?
A. To prevent the compressor motor from overloading during a hot pull-down.
B. To maintain a minimum pressure in the evaporator.
, C. To regulate the oil pressure in the crankcase.
D. To ensure liquid refrigerant returns to the compressor.
Answer: A
Conceptual Explanation: A CPR valve limits the suction pressure entering the compressor,
which prevents the motor from drawing excessive current during high-load conditions,
such as after a defrost cycle or initial startup.
5. A technician finds a commercial system with high discharge pressure and high subcooling.
What is the most likely cause?
A. Dirty condenser coils.
B. Inoperative condenser fan motor.
C. Non-condensables in the system.
D. Overcharge of refrigerant.
Answer: D
Conceptual Explanation: An overcharge leads to liquid backing up in the condenser,
which increases the pressure and provides more area for subcooling the liquid. Dirty coils
or non-condensables usually cause high pressure but low to normal subcooling.
6. Which ASHRAE safety classification represents a refrigerant with high toxicity and no flame
propagation?
A. B1
REFRIGERATION PRACTICE EXAM
QUESTIONS AND VERIFIED ANSWERS
JUST RELEASED.
1. In a commercial refrigeration system using a Thermostatic Expansion Valve (TXV), what is
the primary purpose of the external equalizer line?
A. To bypass liquid refrigerant directly into the suction line.
B. To balance the pressure between the high side and low side during the off-cycle.
C. To increase the superheat setting for better compressor protection.
D. To compensate for the pressure drop across the evaporator coil.
Answer: D
Conceptual Explanation: An external equalizer line is used when there is a significant
pressure drop across the evaporator. It allows the TXV to sense the pressure at the
evaporator outlet rather than the inlet, ensuring accurate superheat control.
2. Which of the following describes the ‘Net Refrigeration Effect’ (NRE)?
A. The difference in enthalpy between the refrigerant entering the evaporator and leaving
the evaporator.
B. The total heat rejected by the condenser.
,C. The ratio of the heat of compression to the evaporator load.
D. The total energy consumed by the compressor motor in BTUs.
Answer: A
Conceptual Explanation: NRE is the amount of heat absorbed by each pound of
refrigerant as it passes through the evaporator, calculated as the difference in enthalpy
(Btu/lb) between the evaporator inlet and outlet.
3. When installing a walk-in freezer, why must the drain line be wrapped with heat tape and
insulated?
A. To prevent the condensate from boiling inside the pipe.
B. To maintain the temperature of the walk-in box.
C. To increase the efficiency of the defrost cycle.
D. To prevent the condensate water from freezing and clogging the line.
Answer: D
Conceptual Explanation: In low-temperature applications (freezers), condensate water
will freeze inside the drain line because the ambient temperature of the room is below
freezing. Heat tape prevents ice buildup.
4. What is the function of a Crankcase Pressure Regulator (CPR) valve?
A. To prevent the compressor motor from overloading during a hot pull-down.
B. To maintain a minimum pressure in the evaporator.
, C. To regulate the oil pressure in the crankcase.
D. To ensure liquid refrigerant returns to the compressor.
Answer: A
Conceptual Explanation: A CPR valve limits the suction pressure entering the compressor,
which prevents the motor from drawing excessive current during high-load conditions,
such as after a defrost cycle or initial startup.
5. A technician finds a commercial system with high discharge pressure and high subcooling.
What is the most likely cause?
A. Dirty condenser coils.
B. Inoperative condenser fan motor.
C. Non-condensables in the system.
D. Overcharge of refrigerant.
Answer: D
Conceptual Explanation: An overcharge leads to liquid backing up in the condenser,
which increases the pressure and provides more area for subcooling the liquid. Dirty coils
or non-condensables usually cause high pressure but low to normal subcooling.
6. Which ASHRAE safety classification represents a refrigerant with high toxicity and no flame
propagation?
A. B1
