Master HVAC Technician Examination
Exam Practice Questions And Correct
Answers (Verified Answers) Plus
Rationale 2026 Q&A| Instant Download
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1. A residential split air-conditioning system is reported to have
insufficient cooling despite the compressor running continuously. The
technician measures normal refrigerant charge, clean filters, and
proper thermostat operation. Which of the following is the most likely
cause of reduced cooling performance in this scenario?
A. Oversized condenser fan motor
B. Restricted airflow across the evaporator coil due to a dirty blower
wheel
C. Excessively high subcooling in the condenser
D. Thermostat differential set too narrow
, Correct answer: B. Restricted airflow across the evaporator coil due
to a dirty blower wheel
Rationale: When refrigerant charge and controls are normal but
cooling is weak, insufficient airflow across the evaporator is a
common cause because it reduces heat absorption and system
capacity.
2. In a vapor-compression refrigeration cycle, what is the primary
function of the expansion device?
A. Increase refrigerant pressure before the evaporator
B. Remove latent heat from the refrigerant
C. Meter refrigerant flow and reduce pressure before evaporation
D. Compress refrigerant vapor into liquid state
Correct answer: C. Meter refrigerant flow and reduce pressure before
evaporation
Rationale: The expansion device regulates refrigerant flow and
causes a pressure drop so the refrigerant can evaporate and absorb
heat efficiently in the evaporator.
3. A technician notices high head pressure in a system using air-cooled
condensers. Ambient temperature is normal, and refrigerant charge is
correct. What is the most probable cause?
A. Overcharged evaporator coil
B. Dirty condenser coil restricting heat rejection
C. Low compressor oil level
, D. Faulty low-pressure switch
Correct answer: B. Dirty condenser coil restricting heat rejection
Rationale: Reduced heat transfer at the condenser due to fouling
causes elevated condensing pressure even when refrigerant charge is
correct.
4. What is the main purpose of superheat in a refrigeration system?
A. To ensure liquid refrigerant enters the compressor
B. To confirm complete evaporation before suction gas reaches the
compressor
C. To increase condenser efficiency
D. To reduce refrigerant mass flow rate
Correct answer: B. To confirm complete evaporation before suction
gas reaches the compressor
Rationale: Superheat ensures that only vapor enters the compressor,
preventing liquid slugging and mechanical damage.
5. A scroll compressor is overheating and tripping its thermal overload.
Which condition is most likely responsible?
A. Excessively low suction pressure causing insufficient cooling of
motor windings
B. Oversized evaporator coil
C. Excessive subcooling
D. High refrigerant viscosity
Correct answer: A. Excessively low suction pressure causing
, insufficient cooling of motor windings
Rationale: Low suction pressure reduces refrigerant mass flow,
limiting cooling of compressor motor windings and causing
overheating.
6. Which refrigerant property is most critical when selecting a
replacement refrigerant for an existing system?
A. Color of refrigerant cylinder
B. Compatibility with system lubricants and operating pressures
C. Brand of refrigerant manufacturer
D. Odor of refrigerant
Correct answer: B. Compatibility with system lubricants and
operating pressures
Rationale: Refrigerant must be compatible with system materials,
lubricants, and pressure characteristics to ensure safe operation.
7. What is the effect of non-condensable gases in a refrigeration system?
A. Lower discharge pressure
B. Increase evaporator efficiency
C. Raise head pressure and reduce system efficiency
D. Improve compressor lubrication
Correct answer: C. Raise head pressure and reduce system efficiency
Rationale: Non-condensable gases accumulate in the condenser,
increasing pressure and reducing heat transfer efficiency.
Exam Practice Questions And Correct
Answers (Verified Answers) Plus
Rationale 2026 Q&A| Instant Download
1. A residential split air-conditioning system is reported to have
insufficient cooling despite the compressor running continuously. The
technician measures normal refrigerant charge, clean filters, and
proper thermostat operation. Which of the following is the most likely
cause of reduced cooling performance in this scenario?
A. Oversized condenser fan motor
B. Restricted airflow across the evaporator coil due to a dirty blower
wheel
C. Excessively high subcooling in the condenser
D. Thermostat differential set too narrow
, Correct answer: B. Restricted airflow across the evaporator coil due
to a dirty blower wheel
Rationale: When refrigerant charge and controls are normal but
cooling is weak, insufficient airflow across the evaporator is a
common cause because it reduces heat absorption and system
capacity.
2. In a vapor-compression refrigeration cycle, what is the primary
function of the expansion device?
A. Increase refrigerant pressure before the evaporator
B. Remove latent heat from the refrigerant
C. Meter refrigerant flow and reduce pressure before evaporation
D. Compress refrigerant vapor into liquid state
Correct answer: C. Meter refrigerant flow and reduce pressure before
evaporation
Rationale: The expansion device regulates refrigerant flow and
causes a pressure drop so the refrigerant can evaporate and absorb
heat efficiently in the evaporator.
3. A technician notices high head pressure in a system using air-cooled
condensers. Ambient temperature is normal, and refrigerant charge is
correct. What is the most probable cause?
A. Overcharged evaporator coil
B. Dirty condenser coil restricting heat rejection
C. Low compressor oil level
, D. Faulty low-pressure switch
Correct answer: B. Dirty condenser coil restricting heat rejection
Rationale: Reduced heat transfer at the condenser due to fouling
causes elevated condensing pressure even when refrigerant charge is
correct.
4. What is the main purpose of superheat in a refrigeration system?
A. To ensure liquid refrigerant enters the compressor
B. To confirm complete evaporation before suction gas reaches the
compressor
C. To increase condenser efficiency
D. To reduce refrigerant mass flow rate
Correct answer: B. To confirm complete evaporation before suction
gas reaches the compressor
Rationale: Superheat ensures that only vapor enters the compressor,
preventing liquid slugging and mechanical damage.
5. A scroll compressor is overheating and tripping its thermal overload.
Which condition is most likely responsible?
A. Excessively low suction pressure causing insufficient cooling of
motor windings
B. Oversized evaporator coil
C. Excessive subcooling
D. High refrigerant viscosity
Correct answer: A. Excessively low suction pressure causing
, insufficient cooling of motor windings
Rationale: Low suction pressure reduces refrigerant mass flow,
limiting cooling of compressor motor windings and causing
overheating.
6. Which refrigerant property is most critical when selecting a
replacement refrigerant for an existing system?
A. Color of refrigerant cylinder
B. Compatibility with system lubricants and operating pressures
C. Brand of refrigerant manufacturer
D. Odor of refrigerant
Correct answer: B. Compatibility with system lubricants and
operating pressures
Rationale: Refrigerant must be compatible with system materials,
lubricants, and pressure characteristics to ensure safe operation.
7. What is the effect of non-condensable gases in a refrigeration system?
A. Lower discharge pressure
B. Increase evaporator efficiency
C. Raise head pressure and reduce system efficiency
D. Improve compressor lubrication
Correct answer: C. Raise head pressure and reduce system efficiency
Rationale: Non-condensable gases accumulate in the condenser,
increasing pressure and reducing heat transfer efficiency.
