Louisiana (New Orleans) Second Class Stationary Air
Conditioning – 640-LA Contractor Exam 100 Questions
with Correct Answers & Explanations | Graded A+ Study
Guide download instant pdf.
1. What is the primary function of a compressor in a refrigeration
system?
A. To absorb heat
B. To condense refrigerant
C. To raise the pressure and temperature of refrigerant vapor
D. To meter refrigerant flow
The compressor increases refrigerant pressure and temperature so
heat can be rejected in the condenser.
2. Which refrigerant property allows heat transfer during
evaporation?
A. Density
B. Latent heat
C. Viscosity
D. Specific gravity
Latent heat allows refrigerant to absorb large amounts of heat
during phase change.
3. What component prevents liquid refrigerant from entering the
compressor?
A. Expansion valve
B. Accumulator
C. Receiver
D. Filter drier
An accumulator stores excess liquid refrigerant and protects the
compressor.
4. What is the normal function of a condenser?
A. Absorb heat from air
B. Reject heat to the surroundings
, C. Increase refrigerant pressure
D. Control refrigerant flow
The condenser removes heat from high-pressure refrigerant vapor.
5. Which tool is used to measure superheat?
A. Manifold gauge only
B. Thermometer and pressure gauge
C. Psychrometer
D. Anemometer
Superheat requires both temperature and pressure measurements.
6. What does subcooling indicate in a refrigeration system?
A. Excess air in system
B. Liquid refrigerant temperature below saturation
C. Compressor inefficiency
D. Evaporator flooding
Subcooling ensures liquid refrigerant reaches the metering device.
7. Which electrical device protects motors from overheating?
A. Fuse
B. Circuit breaker
C. Thermal overload
D. Contactor
Thermal overloads respond to excessive motor temperature or
current.
8. What is the purpose of a filter drier?
A. Increase refrigerant pressure
B. Remove moisture and contaminants
C. Control refrigerant flow
D. Store refrigerant
Moisture and debris can damage system components.
9. What unit is commonly used to measure cooling capacity?
A. Watts
B. PSI
C. BTU per hour
D. Volts
Cooling capacity is measured as heat removed per hour.
, 10. Which law explains the relationship between pressure and
temperature of a gas?
A. Ohm’s Law
B. Boyle’s Law
C. Gay-Lussac’s Law
D. Faraday’s Law
Gas temperature and pressure rise and fall together at constant
volume.
11. What happens to amperage when motor load increases?
A. Decreases
B. Remains constant
C. Increases
D. Drops to zero
Higher mechanical load draws more current.
12. Which component controls refrigerant flow into the
evaporator?
A. Compressor
B. Condenser
C. Metering device
D. Accumulator
Metering devices regulate refrigerant entering the evaporator.
13. What is the main hazard of refrigerant exposure?
A. Fire
B. Explosion
C. Asphyxiation
D. Electric shock
Refrigerants displace oxygen in confined spaces.
14. Which instrument measures airflow?
A. Manometer
B. Anemometer
C. Voltmeter
D. Clamp meter
Anemometers measure air velocity and volume.
15. What is the typical voltage for commercial HVAC motors?
A. 120V
Conditioning – 640-LA Contractor Exam 100 Questions
with Correct Answers & Explanations | Graded A+ Study
Guide download instant pdf.
1. What is the primary function of a compressor in a refrigeration
system?
A. To absorb heat
B. To condense refrigerant
C. To raise the pressure and temperature of refrigerant vapor
D. To meter refrigerant flow
The compressor increases refrigerant pressure and temperature so
heat can be rejected in the condenser.
2. Which refrigerant property allows heat transfer during
evaporation?
A. Density
B. Latent heat
C. Viscosity
D. Specific gravity
Latent heat allows refrigerant to absorb large amounts of heat
during phase change.
3. What component prevents liquid refrigerant from entering the
compressor?
A. Expansion valve
B. Accumulator
C. Receiver
D. Filter drier
An accumulator stores excess liquid refrigerant and protects the
compressor.
4. What is the normal function of a condenser?
A. Absorb heat from air
B. Reject heat to the surroundings
, C. Increase refrigerant pressure
D. Control refrigerant flow
The condenser removes heat from high-pressure refrigerant vapor.
5. Which tool is used to measure superheat?
A. Manifold gauge only
B. Thermometer and pressure gauge
C. Psychrometer
D. Anemometer
Superheat requires both temperature and pressure measurements.
6. What does subcooling indicate in a refrigeration system?
A. Excess air in system
B. Liquid refrigerant temperature below saturation
C. Compressor inefficiency
D. Evaporator flooding
Subcooling ensures liquid refrigerant reaches the metering device.
7. Which electrical device protects motors from overheating?
A. Fuse
B. Circuit breaker
C. Thermal overload
D. Contactor
Thermal overloads respond to excessive motor temperature or
current.
8. What is the purpose of a filter drier?
A. Increase refrigerant pressure
B. Remove moisture and contaminants
C. Control refrigerant flow
D. Store refrigerant
Moisture and debris can damage system components.
9. What unit is commonly used to measure cooling capacity?
A. Watts
B. PSI
C. BTU per hour
D. Volts
Cooling capacity is measured as heat removed per hour.
, 10. Which law explains the relationship between pressure and
temperature of a gas?
A. Ohm’s Law
B. Boyle’s Law
C. Gay-Lussac’s Law
D. Faraday’s Law
Gas temperature and pressure rise and fall together at constant
volume.
11. What happens to amperage when motor load increases?
A. Decreases
B. Remains constant
C. Increases
D. Drops to zero
Higher mechanical load draws more current.
12. Which component controls refrigerant flow into the
evaporator?
A. Compressor
B. Condenser
C. Metering device
D. Accumulator
Metering devices regulate refrigerant entering the evaporator.
13. What is the main hazard of refrigerant exposure?
A. Fire
B. Explosion
C. Asphyxiation
D. Electric shock
Refrigerants displace oxygen in confined spaces.
14. Which instrument measures airflow?
A. Manometer
B. Anemometer
C. Voltmeter
D. Clamp meter
Anemometers measure air velocity and volume.
15. What is the typical voltage for commercial HVAC motors?
A. 120V
