UA STAR HVACR Mastery Certification
Exam With Actual Questions & Verified
Answers, Plus Explained
Rationales/Expert Verified For
Guaranteed 100% Pass 2026/Latest
Update/Instant Download Pdf
1. Which of the following best describes superheat in a refrigeration
system?
A) The temperature of the refrigerant at the condenser outlet
B) The difference between the refrigerant’s actual temperature
and its saturation temperature at the evaporator pressure
C) The temperature drop across the expansion device
D) The pressure difference between the high and low sides
B) The difference between the refrigerant’s actual temperature and
its saturation temperature at the evaporator pressure
Superheat ensures that only vapor enters the compressor, preventing
liquid refrigerant damage.
2. What is the primary purpose of a TXV (Thermostatic Expansion
Valve)?
A) To regulate condenser pressure
B) To control refrigerant flow into the evaporator
C) To remove moisture from the system
D) To increase superheat
,B) To control refrigerant flow into the evaporator
TXVs maintain proper evaporator load by adjusting refrigerant flow
based on superheat, improving efficiency and protecting the
compressor.
3. Which type of compressor is most commonly used in large
commercial HVACR systems?
A) Reciprocating
B) Scroll
C) Centrifugal
D) Rotary
C) Centrifugal
Centrifugal compressors are preferred for large systems due to high
capacity, efficiency, and smooth operation.
4. What is the primary function of a receiver in a refrigeration
system?
A) To increase system pressure
B) To store liquid refrigerant
C) To remove oil from refrigerant
D) To regulate compressor speed
B) To store liquid refrigerant
Receivers provide a reservoir of liquid refrigerant, ensuring proper
supply to the expansion device.
5. Which of the following describes subcooling?
A) Cooling of refrigerant vapor below the saturation temperature
B) Cooling of liquid refrigerant below its saturation temperature
C) Heating of refrigerant above saturation
D) Condensation of refrigerant in the evaporator
,B) Cooling of liquid refrigerant below its saturation temperature
Subcooling increases system efficiency by ensuring liquid refrigerant
enters the expansion device without vapor.
6. What safety device protects the compressor from overpressure in
the discharge line?
A) Low-pressure switch
B) Relief valve
C) TXV
D) Solenoid valve
B) Relief valve
Relief valves prevent excessive pressure buildup that could damage
the compressor or piping.
7. Which refrigerant type is classified as HFC (hydrofluorocarbon)?
A) R-22
B) R-134a
C) R-123
D) Ammonia
B) R-134a
R-134a is a common HFC refrigerant with zero ozone depletion
potential.
8. In a VAV system, the main purpose of the terminal unit is to:
A) Control compressor speed
B) Modulate airflow to the conditioned space
C) Heat the refrigerant
D) Increase static pressure in ductwork
B) Modulate airflow to the conditioned space
VAV terminal units adjust airflow based on space demand, improving
comfort and energy efficiency.
, 9. Which type of coil is typically used for heat recovery in HVAC
systems?
A) Evaporator coil
B) Condenser coil
C) Plate-fin coil
D) DX coil
C) Plate-fin coil
Plate-fin coils are compact, efficient, and ideal for transferring heat
between streams in heat recovery applications.
10. What is the main purpose of a crankcase heater on a
refrigeration compressor?
A) Reduce oil foaming
B) Prevent refrigerant migration and oil dilution during shutdown
C) Increase refrigerant superheat
D) Reduce subcooling
B) Prevent refrigerant migration and oil dilution during shutdown
Crankcase heaters prevent liquid refrigerant from mixing with oil,
which can damage the compressor at startup.
11. In a direct expansion (DX) cooling system, what controls
indoor humidity?
A) Compressor speed
B) Condenser fan
C) Coil surface temperature and airflow
D) Expansion valve size
C) Coil surface temperature and airflow
Lower coil temperatures and proper airflow allow moisture to
condense out of the air, controlling humidity.
Exam With Actual Questions & Verified
Answers, Plus Explained
Rationales/Expert Verified For
Guaranteed 100% Pass 2026/Latest
Update/Instant Download Pdf
1. Which of the following best describes superheat in a refrigeration
system?
A) The temperature of the refrigerant at the condenser outlet
B) The difference between the refrigerant’s actual temperature
and its saturation temperature at the evaporator pressure
C) The temperature drop across the expansion device
D) The pressure difference between the high and low sides
B) The difference between the refrigerant’s actual temperature and
its saturation temperature at the evaporator pressure
Superheat ensures that only vapor enters the compressor, preventing
liquid refrigerant damage.
2. What is the primary purpose of a TXV (Thermostatic Expansion
Valve)?
A) To regulate condenser pressure
B) To control refrigerant flow into the evaporator
C) To remove moisture from the system
D) To increase superheat
,B) To control refrigerant flow into the evaporator
TXVs maintain proper evaporator load by adjusting refrigerant flow
based on superheat, improving efficiency and protecting the
compressor.
3. Which type of compressor is most commonly used in large
commercial HVACR systems?
A) Reciprocating
B) Scroll
C) Centrifugal
D) Rotary
C) Centrifugal
Centrifugal compressors are preferred for large systems due to high
capacity, efficiency, and smooth operation.
4. What is the primary function of a receiver in a refrigeration
system?
A) To increase system pressure
B) To store liquid refrigerant
C) To remove oil from refrigerant
D) To regulate compressor speed
B) To store liquid refrigerant
Receivers provide a reservoir of liquid refrigerant, ensuring proper
supply to the expansion device.
5. Which of the following describes subcooling?
A) Cooling of refrigerant vapor below the saturation temperature
B) Cooling of liquid refrigerant below its saturation temperature
C) Heating of refrigerant above saturation
D) Condensation of refrigerant in the evaporator
,B) Cooling of liquid refrigerant below its saturation temperature
Subcooling increases system efficiency by ensuring liquid refrigerant
enters the expansion device without vapor.
6. What safety device protects the compressor from overpressure in
the discharge line?
A) Low-pressure switch
B) Relief valve
C) TXV
D) Solenoid valve
B) Relief valve
Relief valves prevent excessive pressure buildup that could damage
the compressor or piping.
7. Which refrigerant type is classified as HFC (hydrofluorocarbon)?
A) R-22
B) R-134a
C) R-123
D) Ammonia
B) R-134a
R-134a is a common HFC refrigerant with zero ozone depletion
potential.
8. In a VAV system, the main purpose of the terminal unit is to:
A) Control compressor speed
B) Modulate airflow to the conditioned space
C) Heat the refrigerant
D) Increase static pressure in ductwork
B) Modulate airflow to the conditioned space
VAV terminal units adjust airflow based on space demand, improving
comfort and energy efficiency.
, 9. Which type of coil is typically used for heat recovery in HVAC
systems?
A) Evaporator coil
B) Condenser coil
C) Plate-fin coil
D) DX coil
C) Plate-fin coil
Plate-fin coils are compact, efficient, and ideal for transferring heat
between streams in heat recovery applications.
10. What is the main purpose of a crankcase heater on a
refrigeration compressor?
A) Reduce oil foaming
B) Prevent refrigerant migration and oil dilution during shutdown
C) Increase refrigerant superheat
D) Reduce subcooling
B) Prevent refrigerant migration and oil dilution during shutdown
Crankcase heaters prevent liquid refrigerant from mixing with oil,
which can damage the compressor at startup.
11. In a direct expansion (DX) cooling system, what controls
indoor humidity?
A) Compressor speed
B) Condenser fan
C) Coil surface temperature and airflow
D) Expansion valve size
C) Coil surface temperature and airflow
Lower coil temperatures and proper airflow allow moisture to
condense out of the air, controlling humidity.
