NEVADA C-21 REFRIGERATION & AIR
CONDITIONING CONTRACTOR EXAM
QUESTIONS AND VERIFIED ANSWERS
JUST RELEASED.
1. When calculating the required ventilation for a machinery room containing R-134a, what is
the primary factor used to determine the airflow rate according to the Uniform Mechanical
Code (UMC)?
A. The total horsepower of the compressors in the room
B. The volume of the machinery room
C. The floor area of the machinery room
D. The mass of refrigerant in the largest system located in the room
Answer: D
Conceptual Explanation: Per UMC and ASHRAE 15, ventilation requirements for
machinery rooms are calculated based on the mass of refrigerant (usually the square root
of the mass) to ensure adequate dilution in the event of a leak.
2. In a water-cooled condenser, what is the typical result of high non-condensable gases in
the system?
A. Decreased discharge pressure and decreased subcooling
,B. Increased discharge pressure and increased subcooling
C. Low suction pressure and high superheat
D. Increased discharge pressure and constant or decreased subcooling
Answer: D
Conceptual Explanation: Non-condensables collect in the condenser, reducing the
effective surface area for heat exchange, which spikes discharge pressure, but they do not
contribute to subcooling.
3. According to Nevada regulations and the UMC, what is the minimum clearance required in
front of the service side of a furnace or air handler located in an attic?
A. 30 inches
B. 24 inches
C. 36 inches
D. 48 inches
Answer: A
Conceptual Explanation: The standard code requirement for service clearance in front of
equipment is 30 inches to allow technicians adequate room for maintenance.
4. Which of the following describes the ‘Approach’ temperature of a cooling tower?
A. The difference between the hot water inlet and the cold water outlet
B. The difference between the entering air dry-bulb and wet-bulb temperatures
, C. The difference between the cold water outlet and the entering air wet-bulb temperature
D. The difference between the condenser water supply and return temperatures
Answer: C
Conceptual Explanation: Approach is the measure of how close the cooling tower can cool
the water to the ambient wet-bulb temperature, which is the theoretical limit.
5. A 3-phase motor is exhibiting high vibration and drawing unequal current across its legs. A
voltage check shows 230V, 230V, and 205V. What is the most likely cause?
A. Open start capacitor
B. Mechanical bearing failure
C. Voltage imbalance causing current imbalance
D. Shorted run winding
Answer: C
Conceptual Explanation: Voltage imbalance in 3-phase systems causes significant current
imbalance (often 6-10 times the voltage imbalance percentage), leading to overheating and
vibration.
6. In a refrigeration system utilizing a Thermostatic Expansion Valve (TXV), what happens to
the valve if the sensing bulb loses its charge?
A. The valve opens wide, flooding the evaporator
B. The valve remains in its last position
CONDITIONING CONTRACTOR EXAM
QUESTIONS AND VERIFIED ANSWERS
JUST RELEASED.
1. When calculating the required ventilation for a machinery room containing R-134a, what is
the primary factor used to determine the airflow rate according to the Uniform Mechanical
Code (UMC)?
A. The total horsepower of the compressors in the room
B. The volume of the machinery room
C. The floor area of the machinery room
D. The mass of refrigerant in the largest system located in the room
Answer: D
Conceptual Explanation: Per UMC and ASHRAE 15, ventilation requirements for
machinery rooms are calculated based on the mass of refrigerant (usually the square root
of the mass) to ensure adequate dilution in the event of a leak.
2. In a water-cooled condenser, what is the typical result of high non-condensable gases in
the system?
A. Decreased discharge pressure and decreased subcooling
,B. Increased discharge pressure and increased subcooling
C. Low suction pressure and high superheat
D. Increased discharge pressure and constant or decreased subcooling
Answer: D
Conceptual Explanation: Non-condensables collect in the condenser, reducing the
effective surface area for heat exchange, which spikes discharge pressure, but they do not
contribute to subcooling.
3. According to Nevada regulations and the UMC, what is the minimum clearance required in
front of the service side of a furnace or air handler located in an attic?
A. 30 inches
B. 24 inches
C. 36 inches
D. 48 inches
Answer: A
Conceptual Explanation: The standard code requirement for service clearance in front of
equipment is 30 inches to allow technicians adequate room for maintenance.
4. Which of the following describes the ‘Approach’ temperature of a cooling tower?
A. The difference between the hot water inlet and the cold water outlet
B. The difference between the entering air dry-bulb and wet-bulb temperatures
, C. The difference between the cold water outlet and the entering air wet-bulb temperature
D. The difference between the condenser water supply and return temperatures
Answer: C
Conceptual Explanation: Approach is the measure of how close the cooling tower can cool
the water to the ambient wet-bulb temperature, which is the theoretical limit.
5. A 3-phase motor is exhibiting high vibration and drawing unequal current across its legs. A
voltage check shows 230V, 230V, and 205V. What is the most likely cause?
A. Open start capacitor
B. Mechanical bearing failure
C. Voltage imbalance causing current imbalance
D. Shorted run winding
Answer: C
Conceptual Explanation: Voltage imbalance in 3-phase systems causes significant current
imbalance (often 6-10 times the voltage imbalance percentage), leading to overheating and
vibration.
6. In a refrigeration system utilizing a Thermostatic Expansion Valve (TXV), what happens to
the valve if the sensing bulb loses its charge?
A. The valve opens wide, flooding the evaporator
B. The valve remains in its last position
