NEVADA (NV) C-21B AIR CONDITIONING
CONTRACTOR PRACTICE EXAM — COMPREHENSIVE
EXAM PREPARATION, ACTUAL STUDY GUIDE & FULL
TESTBANK — 150 ADVANCED PRACTICE QUESTIONS
& 100% CORRECT ANSWERS WITH RATIONALES —
2026/2027 LATEST UPDATE
TABLE OF CONTENTS
i. Piping, Insulation, Hangers & Supports
ii. Sound, Vibration & Seismic Control
iii. Heating & Cooling Principles
iv. Refrigerants & Refrigeration Systems
v. Load Calculations
vi. Testing, Adjusting & Balancing
vii. Controls & Control Circuits
viii. Air-Conditioning & Heat-Pump Equipment
ix. Furnaces & Heaters
x. Chimneys, Flues, Vents & Combustion Air
xi. Fuel Systems
xii. Duct Design, Installation & Air Distribution
xiii. Evaporative Cooling
xiv. Safety, Troubleshooting & Professional Judgment
xv. Nevada C-21B Scope, Compliance & Licensing Applications
DESCRIPTION
This comprehensive Nevada C-21B Air Conditioning Contractor practice
examination is designed for contractors, technicians, apprentices, supervisors,
qualifying individuals, and experienced HVAC professionals preparing for
advanced licensing assessment. It covers piping, insulation, supports, refrigeration,
load calculations, controls, air-conditioning and heat-pump equipment, furnaces,
fuel systems, ductwork, evaporative cooling, combustion air, ventilation, testing,
troubleshooting, safety, and professional decision-making. The practice set
contains 150 challenging questions and answers with concise rationales designed
to reinforce application rather than simple memorization. Questions emphasize
realistic field situations, calculations, code interpretation, diagnosis, compliance,
and professional judgment. Purchase and instantly get a downloadable and
editable PDF for convenient study and review. The current PSI outline identifies 60
,scored questions, a 42-question passing score, and a two-hour testing period for
the C-21B examination.
QUESTIONS 1–150
Question 1
A C-21B contractor is installing a split-system air conditioner. The suction line
must travel substantially farther than the manufacturer's standard piping length.
Which design consideration is MOST important before installation?
A. Increase the suction-line diameter without checking the manufacturer
B. Follow the manufacturer's allowable equivalent length, elevation, oil-return
requirements, and line-sizing procedure
C. Reduce the liquid-line diameter to increase refrigerant velocity
D. Install the suction line without insulation because it operates at low
temperature
🔴 Correct Answer: B. Follow the manufacturer's allowable equivalent length,
elevation, oil-return requirements, and line-sizing procedure.
🔵 Explanation: Long refrigerant lines can alter pressure drop, oil return, refrigerant
charge, and system capacity. Proper sizing must account for the manufacturer's
approved piping configuration rather than relying on a generic diameter change.
Question 2
A refrigeration system has a long horizontal suction line with several fittings. The
technician observes poor compressor oil return. Which condition is MOST likely
contributing?
A. Excessive suction-line velocity reduction
B. Excessively high liquid-line velocity
C. Excessive condenser airflow
D. Excessive evaporator superheat caused only by the thermostat
🔴 Correct Answer: A. Excessive suction-line velocity reduction.
🔵 Explanation: Suction piping must maintain adequate refrigerant velocity to
entrain and return oil to the compressor. Oversized piping can reduce velocity
sufficiently to impair oil return.
Question 3
A contractor is routing condensate piping through an unconditioned attic in a hot
desert climate. Which measure is MOST appropriate when condensation on the
,outside of the drain piping could damage surrounding materials?
A. Increase refrigerant charge
B. Insulate the condensate piping where condensation is expected
C. Install a larger compressor
D. Eliminate the drain trap
🔴 Correct Answer: B. Insulate the condensate piping where condensation is
expected.
🔵 Explanation: A cold condensate line can reach a surface temperature below the
surrounding air dew point. Insulation limits exterior condensation and protects
adjacent building components.
Question 4
A suction line is properly sized but contains an unnecessary series of sharp bends.
What is the primary engineering concern?
A. Increased refrigerant pressure drop
B. Increased evaporator surface area
C. Increased condenser capacity
D. Reduced electrical resistance
🔴 Correct Answer: A. Increased refrigerant pressure drop.
🔵 Explanation: Every fitting introduces additional pressure loss. Excessive
equivalent length can reduce evaporator pressure and system capacity even when
the straight-pipe diameter is otherwise correct.
Question 5
A contractor installs refrigerant piping through a wall penetration. Which practice
BEST protects the piping and building assembly?
A. Allow copper tubing to contact sharp masonry edges
B. Provide suitable protection, support, and sealing at the penetration
C. Clamp the tubing tightly against the wall
D. Leave the opening completely unsealed
🔴 Correct Answer: B. Provide suitable protection, support, and sealing at the
penetration.
🔵 Explanation: Penetrations should prevent mechanical damage, unwanted
movement, air leakage, and environmental intrusion while allowing for appropriate
thermal movement.
, Question 6
Two refrigeration lines run together for a substantial distance. Why is proper
separation or insulation between lines important?
A. It prevents electrical current from flowing through copper
B. It prevents unwanted heat transfer and condensation-related problems
C. It increases compressor horsepower
D. It eliminates the need for pressure testing
🔴 Correct Answer: B. It prevents unwanted heat transfer and condensation-
related problems.
🔵 Explanation: Proper insulation and installation prevent undesirable heat
exchange between refrigerant lines and help prevent moisture condensation on cold
surfaces.
Question 7
A liquid line becomes excessively warm while traveling through a high-
temperature attic. What is the primary consequence that should concern the
technician?
A. Increased subcooling automatically
B. Possible flash gas formation and loss of metering performance
C. Guaranteed compressor flooding
D. Increased evaporator airflow
🔴 Correct Answer: B. Possible flash gas formation and loss of metering
performance.
🔵 Explanation: Excessive liquid-line heat gain can reduce available subcooling and
cause liquid refrigerant to partially flash before reaching the metering device,
impairing capacity and control.
Question 8
A duct-supported air handler is mounted above a finished ceiling. Which support
strategy is MOST appropriate?
A. Support the equipment from flexible ductwork
B. Support the equipment using an engineered structural support system
C. Suspend it from ceiling tiles
D. Rest it on the duct liner
CONTRACTOR PRACTICE EXAM — COMPREHENSIVE
EXAM PREPARATION, ACTUAL STUDY GUIDE & FULL
TESTBANK — 150 ADVANCED PRACTICE QUESTIONS
& 100% CORRECT ANSWERS WITH RATIONALES —
2026/2027 LATEST UPDATE
TABLE OF CONTENTS
i. Piping, Insulation, Hangers & Supports
ii. Sound, Vibration & Seismic Control
iii. Heating & Cooling Principles
iv. Refrigerants & Refrigeration Systems
v. Load Calculations
vi. Testing, Adjusting & Balancing
vii. Controls & Control Circuits
viii. Air-Conditioning & Heat-Pump Equipment
ix. Furnaces & Heaters
x. Chimneys, Flues, Vents & Combustion Air
xi. Fuel Systems
xii. Duct Design, Installation & Air Distribution
xiii. Evaporative Cooling
xiv. Safety, Troubleshooting & Professional Judgment
xv. Nevada C-21B Scope, Compliance & Licensing Applications
DESCRIPTION
This comprehensive Nevada C-21B Air Conditioning Contractor practice
examination is designed for contractors, technicians, apprentices, supervisors,
qualifying individuals, and experienced HVAC professionals preparing for
advanced licensing assessment. It covers piping, insulation, supports, refrigeration,
load calculations, controls, air-conditioning and heat-pump equipment, furnaces,
fuel systems, ductwork, evaporative cooling, combustion air, ventilation, testing,
troubleshooting, safety, and professional decision-making. The practice set
contains 150 challenging questions and answers with concise rationales designed
to reinforce application rather than simple memorization. Questions emphasize
realistic field situations, calculations, code interpretation, diagnosis, compliance,
and professional judgment. Purchase and instantly get a downloadable and
editable PDF for convenient study and review. The current PSI outline identifies 60
,scored questions, a 42-question passing score, and a two-hour testing period for
the C-21B examination.
QUESTIONS 1–150
Question 1
A C-21B contractor is installing a split-system air conditioner. The suction line
must travel substantially farther than the manufacturer's standard piping length.
Which design consideration is MOST important before installation?
A. Increase the suction-line diameter without checking the manufacturer
B. Follow the manufacturer's allowable equivalent length, elevation, oil-return
requirements, and line-sizing procedure
C. Reduce the liquid-line diameter to increase refrigerant velocity
D. Install the suction line without insulation because it operates at low
temperature
🔴 Correct Answer: B. Follow the manufacturer's allowable equivalent length,
elevation, oil-return requirements, and line-sizing procedure.
🔵 Explanation: Long refrigerant lines can alter pressure drop, oil return, refrigerant
charge, and system capacity. Proper sizing must account for the manufacturer's
approved piping configuration rather than relying on a generic diameter change.
Question 2
A refrigeration system has a long horizontal suction line with several fittings. The
technician observes poor compressor oil return. Which condition is MOST likely
contributing?
A. Excessive suction-line velocity reduction
B. Excessively high liquid-line velocity
C. Excessive condenser airflow
D. Excessive evaporator superheat caused only by the thermostat
🔴 Correct Answer: A. Excessive suction-line velocity reduction.
🔵 Explanation: Suction piping must maintain adequate refrigerant velocity to
entrain and return oil to the compressor. Oversized piping can reduce velocity
sufficiently to impair oil return.
Question 3
A contractor is routing condensate piping through an unconditioned attic in a hot
desert climate. Which measure is MOST appropriate when condensation on the
,outside of the drain piping could damage surrounding materials?
A. Increase refrigerant charge
B. Insulate the condensate piping where condensation is expected
C. Install a larger compressor
D. Eliminate the drain trap
🔴 Correct Answer: B. Insulate the condensate piping where condensation is
expected.
🔵 Explanation: A cold condensate line can reach a surface temperature below the
surrounding air dew point. Insulation limits exterior condensation and protects
adjacent building components.
Question 4
A suction line is properly sized but contains an unnecessary series of sharp bends.
What is the primary engineering concern?
A. Increased refrigerant pressure drop
B. Increased evaporator surface area
C. Increased condenser capacity
D. Reduced electrical resistance
🔴 Correct Answer: A. Increased refrigerant pressure drop.
🔵 Explanation: Every fitting introduces additional pressure loss. Excessive
equivalent length can reduce evaporator pressure and system capacity even when
the straight-pipe diameter is otherwise correct.
Question 5
A contractor installs refrigerant piping through a wall penetration. Which practice
BEST protects the piping and building assembly?
A. Allow copper tubing to contact sharp masonry edges
B. Provide suitable protection, support, and sealing at the penetration
C. Clamp the tubing tightly against the wall
D. Leave the opening completely unsealed
🔴 Correct Answer: B. Provide suitable protection, support, and sealing at the
penetration.
🔵 Explanation: Penetrations should prevent mechanical damage, unwanted
movement, air leakage, and environmental intrusion while allowing for appropriate
thermal movement.
, Question 6
Two refrigeration lines run together for a substantial distance. Why is proper
separation or insulation between lines important?
A. It prevents electrical current from flowing through copper
B. It prevents unwanted heat transfer and condensation-related problems
C. It increases compressor horsepower
D. It eliminates the need for pressure testing
🔴 Correct Answer: B. It prevents unwanted heat transfer and condensation-
related problems.
🔵 Explanation: Proper insulation and installation prevent undesirable heat
exchange between refrigerant lines and help prevent moisture condensation on cold
surfaces.
Question 7
A liquid line becomes excessively warm while traveling through a high-
temperature attic. What is the primary consequence that should concern the
technician?
A. Increased subcooling automatically
B. Possible flash gas formation and loss of metering performance
C. Guaranteed compressor flooding
D. Increased evaporator airflow
🔴 Correct Answer: B. Possible flash gas formation and loss of metering
performance.
🔵 Explanation: Excessive liquid-line heat gain can reduce available subcooling and
cause liquid refrigerant to partially flash before reaching the metering device,
impairing capacity and control.
Question 8
A duct-supported air handler is mounted above a finished ceiling. Which support
strategy is MOST appropriate?
A. Support the equipment from flexible ductwork
B. Support the equipment using an engineered structural support system
C. Suspend it from ceiling tiles
D. Rest it on the duct liner
