STAR HVAC Mastery Exam
Question 1. Which law of thermodynamics states that energy cannot be created or destroyed in an
isolated system?
A) First Law
B) Second Law
C) Third Law
D) Zeroth Law
Answer: A
Explanation: The First Law of Thermodynamics, also known as the law of conservation of energy, states
that energy cannot be created or destroyed, only transferred or converted within an isolated system.
Question 2. Sensible heat is defined as:
A) Heat involved in changing the phase of a substance
B) Heat that causes a change in temperature without changing phase
C) Heat transferred via radiation
D) Heat stored in a material's chemical bonds
Answer: B
Explanation: Sensible heat changes the temperature of a substance without causing a phase change, as
opposed to latent heat, which involves phase changes.
Question 3. Which heat transfer mechanism involves the transfer of heat through electromagnetic
waves?
A) Conduction
B) Convection
C) Radiation
D) Conduction and convection combined
Answer: C
Explanation: Radiation transfers heat via electromagnetic waves, allowing heat to be transferred
through space without a medium.
Question 4. The U-factor in building insulation measures:
, STAR HVAC Mastery Exam
A) The thermal resistance
B) The rate of heat transfer
C) The amount of moisture vapor diffusion
D) The surface reflectivity
Answer: B
Explanation: The U-factor represents the overall heat transfer coefficient, indicating the rate of heat
transfer through a building component; lower U-factors mean better insulation.
Question 5. On a psychrometric chart, the dry-bulb temperature refers to:
A) The temperature of the water vapor in the air
B) The temperature measured by a standard thermometer
C) The dew point temperature
D) The wet-bulb temperature
Answer: B
Explanation: Dry-bulb temperature is measured by a standard thermometer and indicates the air
temperature without considering humidity.
Question 6. In psychrometrics, humidification involves:
A) Removing moisture from the air
B) Adding moisture to the air
C) Cooling the air below its dew point
D) Decreasing the specific humidity
Answer: B
Explanation: Humidification adds moisture to the air, increasing its humidity level, typically to improve
comfort or process conditions.
Question 7. The vapor-compression refrigeration cycle primarily uses which component to increase the
pressure of refrigerant vapor?
A) Condenser
B) Evaporator
, STAR HVAC Mastery Exam
C) Compressor
D) Expansion valve
Answer: C
Explanation: The compressor increases the pressure of refrigerant vapor, raising its temperature before
it enters the condenser.
Question 8. Which refrigerant property is most directly related to its ozone depletion potential (ODP)?
A) Global Warming Potential (GWP)
B) Chemical composition
C) Pressure-temperature relationship
D) Flammability
Answer: B
Explanation: The chemical composition of refrigerants determines their ozone depletion potential;
chlorofluorocarbons (CFCs) with chlorine are known for high ODP.
Question 9. Ohm's Law is expressed as:
A) V = IR
B) P = IV
C) Q = mcΔT
D) F = ma
Answer: A
Explanation: Ohm's Law states that voltage (V) equals current (I) times resistance (R).
Question 10. A relay in an electrical control circuit is used to:
A) Convert AC to DC
B) Isolate and switch high-power circuits with low-power signals
C) Measure electrical current
D) Step down voltage
Answer: B
, STAR HVAC Mastery Exam
Explanation: Relays act as electrically operated switches, allowing low-voltage control circuits to switch
high-power loads safely.
Question 11. The primary function of a scroll compressor is to:
A) Compress refrigerant via pistons
B) Provide variable capacity operation
C) Compress refrigerant smoothly with fewer moving parts
D) Expand refrigerant into a liquid
Answer: C
Explanation: Scroll compressors use rotating scrolls to compress refrigerant smoothly with fewer parts
and less vibration.
Question 12. An air-cooled condenser removes heat from refrigerant using:
A) Water spray
B) Air circulation over coils
C) Evaporation of water
D) Submersion in a cooling tower
Answer: B
Explanation: Air-cooled condensers use fans to circulate air over coils to remove heat from the
refrigerant.
Question 13. The function of a thermostatic expansion valve (TXV) is to:
A) Compress refrigerant
B) Control refrigerant flow based on superheat
C) Condense refrigerant vapor
D) Evaporate refrigerant
Answer: B
Explanation: The TXV regulates refrigerant flow into the evaporator based on superheat to optimize
performance and prevent liquid flood-back.
Question 1. Which law of thermodynamics states that energy cannot be created or destroyed in an
isolated system?
A) First Law
B) Second Law
C) Third Law
D) Zeroth Law
Answer: A
Explanation: The First Law of Thermodynamics, also known as the law of conservation of energy, states
that energy cannot be created or destroyed, only transferred or converted within an isolated system.
Question 2. Sensible heat is defined as:
A) Heat involved in changing the phase of a substance
B) Heat that causes a change in temperature without changing phase
C) Heat transferred via radiation
D) Heat stored in a material's chemical bonds
Answer: B
Explanation: Sensible heat changes the temperature of a substance without causing a phase change, as
opposed to latent heat, which involves phase changes.
Question 3. Which heat transfer mechanism involves the transfer of heat through electromagnetic
waves?
A) Conduction
B) Convection
C) Radiation
D) Conduction and convection combined
Answer: C
Explanation: Radiation transfers heat via electromagnetic waves, allowing heat to be transferred
through space without a medium.
Question 4. The U-factor in building insulation measures:
, STAR HVAC Mastery Exam
A) The thermal resistance
B) The rate of heat transfer
C) The amount of moisture vapor diffusion
D) The surface reflectivity
Answer: B
Explanation: The U-factor represents the overall heat transfer coefficient, indicating the rate of heat
transfer through a building component; lower U-factors mean better insulation.
Question 5. On a psychrometric chart, the dry-bulb temperature refers to:
A) The temperature of the water vapor in the air
B) The temperature measured by a standard thermometer
C) The dew point temperature
D) The wet-bulb temperature
Answer: B
Explanation: Dry-bulb temperature is measured by a standard thermometer and indicates the air
temperature without considering humidity.
Question 6. In psychrometrics, humidification involves:
A) Removing moisture from the air
B) Adding moisture to the air
C) Cooling the air below its dew point
D) Decreasing the specific humidity
Answer: B
Explanation: Humidification adds moisture to the air, increasing its humidity level, typically to improve
comfort or process conditions.
Question 7. The vapor-compression refrigeration cycle primarily uses which component to increase the
pressure of refrigerant vapor?
A) Condenser
B) Evaporator
, STAR HVAC Mastery Exam
C) Compressor
D) Expansion valve
Answer: C
Explanation: The compressor increases the pressure of refrigerant vapor, raising its temperature before
it enters the condenser.
Question 8. Which refrigerant property is most directly related to its ozone depletion potential (ODP)?
A) Global Warming Potential (GWP)
B) Chemical composition
C) Pressure-temperature relationship
D) Flammability
Answer: B
Explanation: The chemical composition of refrigerants determines their ozone depletion potential;
chlorofluorocarbons (CFCs) with chlorine are known for high ODP.
Question 9. Ohm's Law is expressed as:
A) V = IR
B) P = IV
C) Q = mcΔT
D) F = ma
Answer: A
Explanation: Ohm's Law states that voltage (V) equals current (I) times resistance (R).
Question 10. A relay in an electrical control circuit is used to:
A) Convert AC to DC
B) Isolate and switch high-power circuits with low-power signals
C) Measure electrical current
D) Step down voltage
Answer: B
, STAR HVAC Mastery Exam
Explanation: Relays act as electrically operated switches, allowing low-voltage control circuits to switch
high-power loads safely.
Question 11. The primary function of a scroll compressor is to:
A) Compress refrigerant via pistons
B) Provide variable capacity operation
C) Compress refrigerant smoothly with fewer moving parts
D) Expand refrigerant into a liquid
Answer: C
Explanation: Scroll compressors use rotating scrolls to compress refrigerant smoothly with fewer parts
and less vibration.
Question 12. An air-cooled condenser removes heat from refrigerant using:
A) Water spray
B) Air circulation over coils
C) Evaporation of water
D) Submersion in a cooling tower
Answer: B
Explanation: Air-cooled condensers use fans to circulate air over coils to remove heat from the
refrigerant.
Question 13. The function of a thermostatic expansion valve (TXV) is to:
A) Compress refrigerant
B) Control refrigerant flow based on superheat
C) Condense refrigerant vapor
D) Evaporate refrigerant
Answer: B
Explanation: The TXV regulates refrigerant flow into the evaporator based on superheat to optimize
performance and prevent liquid flood-back.
