NEVADA (NV) C-21B AIR CONDITIONING CONTRACTOR EXAM |
NEVADA C-21B AIR CONDITIONING CONTRACTOR EXAM – 200
QUESTIONS, ANSWERS & RATIONALES
The Nevada C-21B exam is an open-book trade assessment
administered by PSI, testing proficiency across Load Calculations (15%),
Systems & Equipment (25%), Controls (15%), Piping & Refrigerants
(20%), and General Knowledge & Safety (25%). The exam consists of 60
scored questions with a 70% passing score (42/60) and a 2-hour time
limit. The following 200 questions cover all topic areas tested.
1. According to the Uniform Mechanical Code, what is the minimum
clearance required in front of a furnace control side for service and
inspection?
A. 18 inches
B. 30 inches
C. 24 inches
D. 36 inches
Answer: B
Rationale: UMC Section 908.0 requires a minimum 30-inch by 30-inch
working space in front of the control side of an appliance to allow
access for inspection, service, repair, and replacement without
removing permanent construction.
,2. A 5-ton residential split system requires approximately how much
airflow in cooling mode?
A. 1200 CFM
B. 2000 CFM
C. 1600 CFM
D. 2400 CFM
Answer: B
Rationale: The standard airflow requirement is 400 CFM per ton of
cooling capacity. For a 5-ton system: 5 tons × 400 CFM = 2000 CFM.
3. According to UMC Section 310, a horizontal condensate waste pipe
from a cooling coil shall have a slope of not less than:
A. 1/2 inch per foot
B. 1/8 inch per foot
C. 1/4 inch per foot
D. 1 inch per foot
Answer: B
Rationale: UMC 2018 Section 310.1 requires condensate waste piping
to slope not less than 1/8 inch per foot (1 percent) toward the point of
disposal. A flat or reverse-pitched drain holds water and overflows the
pan.
4. A C-21B contractor is installing a new split-system air conditioner.
Where must the liquid line filter-drier be placed for optimal
protection?
,A. At the evaporator outlet
B. At the compressor discharge
C. As close as possible to the metering device inlet
D. At the suction line accumulator inlet
Answer: C
Rationale: Placing the filter-drier just before the metering device
protects the TXV or piston from debris and moisture introduced during
installation.
5. What is the primary function of a refrigerant in an air conditioning
system?
A. To lubricate the compressor
B. To absorb and release heat during phase changes
C. To filter contaminants from the air
D. To generate electrical power for the system
Answer: B
Rationale: Refrigerant is the working fluid that absorbs heat from the
indoor space during evaporation and releases it to the outdoors during
condensation, facilitating heat transfer through phase changes.
6. In the vapor-compression cycle, which component absorbs heat
from the conditioned space?
A. Compressor
B. Condenser
, C. Expansion valve
D. Evaporator
Answer: D
Rationale: The evaporator is where the refrigerant absorbs heat from
the conditioned space, changing from liquid to vapor.
7. 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
Answer: D
Rationale: 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.
8. A homeowner complains that a single zone of their VRF system is
warm while other zones are cooling properly. Which likely cause
should be addressed first?
A. Low refrigerant charge
B. Faulty electronic expansion valve (EEV)
C. Clogged outdoor coil
D. Oversized indoor unit
NEVADA C-21B AIR CONDITIONING CONTRACTOR EXAM – 200
QUESTIONS, ANSWERS & RATIONALES
The Nevada C-21B exam is an open-book trade assessment
administered by PSI, testing proficiency across Load Calculations (15%),
Systems & Equipment (25%), Controls (15%), Piping & Refrigerants
(20%), and General Knowledge & Safety (25%). The exam consists of 60
scored questions with a 70% passing score (42/60) and a 2-hour time
limit. The following 200 questions cover all topic areas tested.
1. According to the Uniform Mechanical Code, what is the minimum
clearance required in front of a furnace control side for service and
inspection?
A. 18 inches
B. 30 inches
C. 24 inches
D. 36 inches
Answer: B
Rationale: UMC Section 908.0 requires a minimum 30-inch by 30-inch
working space in front of the control side of an appliance to allow
access for inspection, service, repair, and replacement without
removing permanent construction.
,2. A 5-ton residential split system requires approximately how much
airflow in cooling mode?
A. 1200 CFM
B. 2000 CFM
C. 1600 CFM
D. 2400 CFM
Answer: B
Rationale: The standard airflow requirement is 400 CFM per ton of
cooling capacity. For a 5-ton system: 5 tons × 400 CFM = 2000 CFM.
3. According to UMC Section 310, a horizontal condensate waste pipe
from a cooling coil shall have a slope of not less than:
A. 1/2 inch per foot
B. 1/8 inch per foot
C. 1/4 inch per foot
D. 1 inch per foot
Answer: B
Rationale: UMC 2018 Section 310.1 requires condensate waste piping
to slope not less than 1/8 inch per foot (1 percent) toward the point of
disposal. A flat or reverse-pitched drain holds water and overflows the
pan.
4. A C-21B contractor is installing a new split-system air conditioner.
Where must the liquid line filter-drier be placed for optimal
protection?
,A. At the evaporator outlet
B. At the compressor discharge
C. As close as possible to the metering device inlet
D. At the suction line accumulator inlet
Answer: C
Rationale: Placing the filter-drier just before the metering device
protects the TXV or piston from debris and moisture introduced during
installation.
5. What is the primary function of a refrigerant in an air conditioning
system?
A. To lubricate the compressor
B. To absorb and release heat during phase changes
C. To filter contaminants from the air
D. To generate electrical power for the system
Answer: B
Rationale: Refrigerant is the working fluid that absorbs heat from the
indoor space during evaporation and releases it to the outdoors during
condensation, facilitating heat transfer through phase changes.
6. In the vapor-compression cycle, which component absorbs heat
from the conditioned space?
A. Compressor
B. Condenser
, C. Expansion valve
D. Evaporator
Answer: D
Rationale: The evaporator is where the refrigerant absorbs heat from
the conditioned space, changing from liquid to vapor.
7. 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
Answer: D
Rationale: 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.
8. A homeowner complains that a single zone of their VRF system is
warm while other zones are cooling properly. Which likely cause
should be addressed first?
A. Low refrigerant charge
B. Faulty electronic expansion valve (EEV)
C. Clogged outdoor coil
D. Oversized indoor unit
