Master HVAC Technician Practice Exam Questions and
correct detailed answers{verified answers}|already graded
A+
1. What is the primary purpose of superheat in a refrigeration system?
A. Increase compressor efficiency
B. Ensure only vapor enters the compressor
C. Reduce condenser pressure
D. Increase refrigerant flow
Answer: B
Superheat ensures all liquid refrigerant has boiled off before reaching the
compressor, preventing damage.
2. Which refrigerant has the highest ozone depletion potential (ODP)?
A. R-134a
B. R-410A
C. R-22
D. R-404A
Answer: C
R-22 is an HCFC with significant ozone depletion potential compared to HFCs.
3. What device meters refrigerant flow based on evaporator outlet
temperature?
A. Capillary tube
B. Fixed orifice
C. Thermostatic expansion valve
D. Liquid line solenoid
Answer: C
TXVs regulate refrigerant flow using a sensing bulb responding to temperature.
4. Excessive subcooling usually indicates:
,A. Low refrigerant charge
B. Overcharged system
C. Restricted airflow
D. Failed compressor
Answer: B
Too much refrigerant causes liquid backup, increasing subcooling.
5. What is the primary function of a liquid receiver?
A. Store refrigerant during pump-down
B. Increase system pressure
C. Prevent oil migration
D. Control evaporator temperature
Answer: A
Receivers hold excess refrigerant during low-load or pump-down conditions.
6. Which motor type is most commonly used in residential HVAC blowers?
A. PSC motor
B. Shaded pole motor
C. Synchronous motor
D. DC series motor
Answer: A
Permanent Split Capacitor motors are common due to reliability and efficiency.
7. What happens when condenser airflow is restricted?
A. Low head pressure
B. High head pressure
C. Low suction pressure
D. Reduced superheat
Answer: B
Poor heat rejection raises condensing temperature and pressure.
, 8. Which instrument measures air velocity?
A. Psychrometer
B. Manometer
C. Anemometer
D. Micron gauge
Answer: C
Anemometers measure air speed in ducts and across coils.
9. What does a micron gauge measure?
A. Refrigerant pressure
B. Vacuum level
C. Airflow volume
D. Oil viscosity
Answer: B
Microns measure deep vacuum levels during evacuation.
10. What is the primary cause of compressor slugging?
A. Excess superheat
B. Liquid refrigerant entering the compressor
C. High discharge pressure
D. Low oil level
Answer: B
Liquid is incompressible and causes mechanical damage.
11. A heat pump operating in heating mode absorbs heat from:
A. Indoor air
B. Electric heaters
C. Outdoor air
D. Compressor windings
Answer: C
Heat pumps extract heat from outside air, even in cold conditions.
correct detailed answers{verified answers}|already graded
A+
1. What is the primary purpose of superheat in a refrigeration system?
A. Increase compressor efficiency
B. Ensure only vapor enters the compressor
C. Reduce condenser pressure
D. Increase refrigerant flow
Answer: B
Superheat ensures all liquid refrigerant has boiled off before reaching the
compressor, preventing damage.
2. Which refrigerant has the highest ozone depletion potential (ODP)?
A. R-134a
B. R-410A
C. R-22
D. R-404A
Answer: C
R-22 is an HCFC with significant ozone depletion potential compared to HFCs.
3. What device meters refrigerant flow based on evaporator outlet
temperature?
A. Capillary tube
B. Fixed orifice
C. Thermostatic expansion valve
D. Liquid line solenoid
Answer: C
TXVs regulate refrigerant flow using a sensing bulb responding to temperature.
4. Excessive subcooling usually indicates:
,A. Low refrigerant charge
B. Overcharged system
C. Restricted airflow
D. Failed compressor
Answer: B
Too much refrigerant causes liquid backup, increasing subcooling.
5. What is the primary function of a liquid receiver?
A. Store refrigerant during pump-down
B. Increase system pressure
C. Prevent oil migration
D. Control evaporator temperature
Answer: A
Receivers hold excess refrigerant during low-load or pump-down conditions.
6. Which motor type is most commonly used in residential HVAC blowers?
A. PSC motor
B. Shaded pole motor
C. Synchronous motor
D. DC series motor
Answer: A
Permanent Split Capacitor motors are common due to reliability and efficiency.
7. What happens when condenser airflow is restricted?
A. Low head pressure
B. High head pressure
C. Low suction pressure
D. Reduced superheat
Answer: B
Poor heat rejection raises condensing temperature and pressure.
, 8. Which instrument measures air velocity?
A. Psychrometer
B. Manometer
C. Anemometer
D. Micron gauge
Answer: C
Anemometers measure air speed in ducts and across coils.
9. What does a micron gauge measure?
A. Refrigerant pressure
B. Vacuum level
C. Airflow volume
D. Oil viscosity
Answer: B
Microns measure deep vacuum levels during evacuation.
10. What is the primary cause of compressor slugging?
A. Excess superheat
B. Liquid refrigerant entering the compressor
C. High discharge pressure
D. Low oil level
Answer: B
Liquid is incompressible and causes mechanical damage.
11. A heat pump operating in heating mode absorbs heat from:
A. Indoor air
B. Electric heaters
C. Outdoor air
D. Compressor windings
Answer: C
Heat pumps extract heat from outside air, even in cold conditions.
