Nevada (NV) C-21B Air Conditioning
Contractor Practice Exam 2 Versions
Description
The Nevada (NV) C-21B Air Conditioning contractor exam is an open-book trade
assessment required for licensing to install and repair residential and commercial HVAC
systems. It is administered by PSI and must be paired with the Construction
Management Survey (CMS) exam to obtain a valid Nevada license.
Core Exam Domains
The exam tests proficiency across the full lifecycle of air conditioning systems:
Load Calculations (15%): Using Manual J, S, and D to determine cooling/heating
requirements and duct sizing.
Systems & Equipment (25%): Installation and operation of A/C units, heat pumps,
furnaces, and ventilation.
Controls (15%): Low-voltage wiring, thermostats, and electrical
safety/troubleshooting.
Piping & Refrigerants (20%): Refrigerant handling (EPA 608), gas piping, and
condensate drainage.
General Knowledge & Safety (25%): Thermodynamics, UMC codes, OSHA safety
standards, and pressure testing.
Nevada C-21B Practice Exam 2 versions
1. According to the Uniform Mechanical Code (UMC), what is the
minimum clearance required in front of a furnace control side for
service and inspection?
A. 18 inches
2026 Question And ANSWER Latest Update
, B. 24 inches
C. 30 inches
D. 36 inches
Answer: C
Rationale: To ensure technician safety and proper tool
maneuverability, the UMC requires a minimum of 30 inches of
working space in front of the control side of the equipment. This
allows for the safe removal of burners, blowers, and controls without
obstruction.
2. When installing a condensate drain line for a high-efficiency
furnace, what is the minimum slope required to ensure proper
drainage?
A. 1/8 inch per foot
B. 1/4 inch per foot
C. 1/2 inch per foot
D. 1 inch per foot
Answer: B
Rationale: Gravity-fed condensate lines must maintain a minimum
slope of 1/4 inch per foot (2% grade). If the slope is too shallow,
biofilm (slime) can build up, leading to clogs, water damage, and
system shutdowns via the float switch.
3. In a heat pump system, the "Reversing Valve" is typically energized
in which mode for most manufacturers?
A. Heating
B. Cooling
C. Defrost only
D. Emergency heat only
Answer: B
Rationale: While some brands vary (like Rheem/Ruud), the industry
standard (Carrier, Trane, Goodman) is for the reversing valve (O-
terminal) to be energized in the cooling mode. This allows the system
2026 Question And ANSWER Latest Update
, to fail-safe into the heating mode during winter if the solenoid coil
fails.
4. What is the maximum permitted length of a flexible air duct (flex
duct) according to standard Nevada energy conservation codes?
A. 5 feet
B. 10 feet
C. 14 feet
D. 25 feet
Answer: C
Rationale: While some jurisdictions allow longer runs, the general
standard for efficiency is to limit flexible ducts to 14 feet. Excessively
long flex duct runs significantly increase static pressure and reduce
airflow due to the internal friction of the wire helix.
5. According to the International Fuel Gas Code (IFGC), a gas shut-off
valve must be located within how many feet of the appliance it
serves?
A. 3 feet
B. 6 feet
C. 10 feet
D. Within the same room, no distance limit
Answer: B
Rationale: The shut-off valve must be in the same room and within 6
feet of the appliance. This ensures that in the event of a gas leak or
fire at the unit, a technician or occupant can quickly and safely isolate
the fuel source.
6. What is the primary purpose of a "Subcooling" measurement when
charging a system with a Thermostatic Expansion Valve (TXV)?
A. To check the evaporator's efficiency.
B. To ensure the condenser is clean.
C. To verify the liquid line has a solid column of refrigerant.
2026 Question And ANSWER Latest Update
, D. To check for non-condensables.
Answer: C
Rationale: Subcooling is the temperature drop of the liquid refrigerant
below its saturation point. For TXV systems, subcooling is the
preferred charging method because the TXV maintains a constant
superheat. High subcooling ensures no vapor bubbles (flash gas)
enter the TXV, which would reduce its capacity.
7. When performing a "Manual J" load calculation, which factor has
the greatest impact on "Sensible Heat Gain" in a Nevada desert
environment?
A. Occupant breathing
B. Latent moisture from showers
C. Solar radiation through windows
D. Cooking appliances
Answer: C
Rationale: In Nevada, solar heat gain through glass is the primary
driver of cooling loads. Manual J places heavy emphasis on window
orientation, glazing types, and shading devices (internal and external)
to determine the peak sensible load.
8. What is the minimum gauge of galvanized steel required for a 12-
inch round supply duct installed in a residential attic?
A. 30 gauge
B. 28 gauge
C. 26 gauge
D. 24 gauge
Answer: B
Rationale: Per UMC Table 602.2, round ducts 14 inches or less in
diameter typically require a minimum of 28-gauge steel. Using thinner
metal can lead to "oil-canning" noise and structural collapse under
high static pressures.
9. A "Category IV" furnace is characterized by:
2026 Question And ANSWER Latest Update
Contractor Practice Exam 2 Versions
Description
The Nevada (NV) C-21B Air Conditioning contractor exam is an open-book trade
assessment required for licensing to install and repair residential and commercial HVAC
systems. It is administered by PSI and must be paired with the Construction
Management Survey (CMS) exam to obtain a valid Nevada license.
Core Exam Domains
The exam tests proficiency across the full lifecycle of air conditioning systems:
Load Calculations (15%): Using Manual J, S, and D to determine cooling/heating
requirements and duct sizing.
Systems & Equipment (25%): Installation and operation of A/C units, heat pumps,
furnaces, and ventilation.
Controls (15%): Low-voltage wiring, thermostats, and electrical
safety/troubleshooting.
Piping & Refrigerants (20%): Refrigerant handling (EPA 608), gas piping, and
condensate drainage.
General Knowledge & Safety (25%): Thermodynamics, UMC codes, OSHA safety
standards, and pressure testing.
Nevada C-21B Practice Exam 2 versions
1. According to the Uniform Mechanical Code (UMC), what is the
minimum clearance required in front of a furnace control side for
service and inspection?
A. 18 inches
2026 Question And ANSWER Latest Update
, B. 24 inches
C. 30 inches
D. 36 inches
Answer: C
Rationale: To ensure technician safety and proper tool
maneuverability, the UMC requires a minimum of 30 inches of
working space in front of the control side of the equipment. This
allows for the safe removal of burners, blowers, and controls without
obstruction.
2. When installing a condensate drain line for a high-efficiency
furnace, what is the minimum slope required to ensure proper
drainage?
A. 1/8 inch per foot
B. 1/4 inch per foot
C. 1/2 inch per foot
D. 1 inch per foot
Answer: B
Rationale: Gravity-fed condensate lines must maintain a minimum
slope of 1/4 inch per foot (2% grade). If the slope is too shallow,
biofilm (slime) can build up, leading to clogs, water damage, and
system shutdowns via the float switch.
3. In a heat pump system, the "Reversing Valve" is typically energized
in which mode for most manufacturers?
A. Heating
B. Cooling
C. Defrost only
D. Emergency heat only
Answer: B
Rationale: While some brands vary (like Rheem/Ruud), the industry
standard (Carrier, Trane, Goodman) is for the reversing valve (O-
terminal) to be energized in the cooling mode. This allows the system
2026 Question And ANSWER Latest Update
, to fail-safe into the heating mode during winter if the solenoid coil
fails.
4. What is the maximum permitted length of a flexible air duct (flex
duct) according to standard Nevada energy conservation codes?
A. 5 feet
B. 10 feet
C. 14 feet
D. 25 feet
Answer: C
Rationale: While some jurisdictions allow longer runs, the general
standard for efficiency is to limit flexible ducts to 14 feet. Excessively
long flex duct runs significantly increase static pressure and reduce
airflow due to the internal friction of the wire helix.
5. According to the International Fuel Gas Code (IFGC), a gas shut-off
valve must be located within how many feet of the appliance it
serves?
A. 3 feet
B. 6 feet
C. 10 feet
D. Within the same room, no distance limit
Answer: B
Rationale: The shut-off valve must be in the same room and within 6
feet of the appliance. This ensures that in the event of a gas leak or
fire at the unit, a technician or occupant can quickly and safely isolate
the fuel source.
6. What is the primary purpose of a "Subcooling" measurement when
charging a system with a Thermostatic Expansion Valve (TXV)?
A. To check the evaporator's efficiency.
B. To ensure the condenser is clean.
C. To verify the liquid line has a solid column of refrigerant.
2026 Question And ANSWER Latest Update
, D. To check for non-condensables.
Answer: C
Rationale: Subcooling is the temperature drop of the liquid refrigerant
below its saturation point. For TXV systems, subcooling is the
preferred charging method because the TXV maintains a constant
superheat. High subcooling ensures no vapor bubbles (flash gas)
enter the TXV, which would reduce its capacity.
7. When performing a "Manual J" load calculation, which factor has
the greatest impact on "Sensible Heat Gain" in a Nevada desert
environment?
A. Occupant breathing
B. Latent moisture from showers
C. Solar radiation through windows
D. Cooking appliances
Answer: C
Rationale: In Nevada, solar heat gain through glass is the primary
driver of cooling loads. Manual J places heavy emphasis on window
orientation, glazing types, and shading devices (internal and external)
to determine the peak sensible load.
8. What is the minimum gauge of galvanized steel required for a 12-
inch round supply duct installed in a residential attic?
A. 30 gauge
B. 28 gauge
C. 26 gauge
D. 24 gauge
Answer: B
Rationale: Per UMC Table 602.2, round ducts 14 inches or less in
diameter typically require a minimum of 28-gauge steel. Using thinner
metal can lead to "oil-canning" noise and structural collapse under
high static pressures.
9. A "Category IV" furnace is characterized by:
2026 Question And ANSWER Latest Update
