Page 1 of 63
Louisiana New Orleans Second Class Stationary Air
Conditioning EXAM QUESTIONS AND CORRECT VERIFIED
SOLUTIONS LATEST UPDATE THIS YEAR – JUST RELEASED
Louisiana New Orleans Second Class Stationary Air Conditioning - 640-LA Contractor Exam
BRIEF EXAM COVERAGE
This exam typically focuses on the practical and technical knowledge needed for stationary air
conditioning systems, basic refrigeration principles, HVAC electrical controls, motors,
compressors, air distribution, piping, maintenance, safety, troubleshooting, and code-related
operational practices.
Main content areas likely covered:
• Refrigeration cycle fundamentals
• Air conditioning system components
• Compressors, condensers, evaporators, metering devices
• Refrigerants and refrigerant handling
• Superheat and subcooling
• Electrical theory and HVAC controls
• Motors, starters, relays, contactors, overloads
• Thermostats and control circuits
• Airflow, duct systems, static pressure, psychrometrics basics
• Chilled water and piping concepts
• Pumps, valves, expansion tanks
Questions 1–50
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1. In a standard vapor-compression air conditioning system, which component is primarily
responsible for raising the pressure and temperature of the refrigerant vapor before it enters
the condenser?
A. Evaporator
B. Metering device
C. Compressor
D. Receiver
Answer: C
Rationale: The compressor raises the refrigerant vapor from low-pressure, low-temperature
vapor to high-pressure, high-temperature vapor, allowing it to reject heat in the condenser.
2. A technician observes frost forming on the suction line near the evaporator and notices
poor cooling performance. Which condition is the most likely cause of this symptom?
A. Excessive airflow across the evaporator
B. Restricted airflow or low evaporator load
C. High condenser fan speed
D. Excessive subcooling only
Answer: B
Rationale: Frost on the suction line often indicates low evaporator temperature, usually caused
by restricted airflow, dirty filters, dirty evaporator coils, or low load conditions.
3. Which electrical instrument is most appropriate for measuring current draw on a running
compressor without disconnecting the circuit conductors?
A. Ohmmeter
B. Clamp ammeter
C. Megohmmeter
D. Continuity tester
Answer: B
Rationale: A clamp ammeter allows current measurement by clamping around a conductor
without opening the circuit, making it ideal for measuring running compressor amperage.
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4. In an air conditioning system, the primary purpose of the condenser is to perform which of
the following functions?
A. Increase superheat
B. Reject heat from the refrigerant to the outside medium
C. Reduce blower speed
D. Increase refrigerant velocity only
Answer: B
Rationale: The condenser rejects heat absorbed from the conditioned space plus the heat of
compression to the surrounding air or water.
5. Which condition is most likely to cause abnormally high head pressure in an air-cooled
condensing unit during normal operating conditions?
A. Dirty condenser coil
B. Low evaporator load only
C. Weak blower motor capacitor
D. Oversized return duct
Answer: A
Rationale: A dirty condenser coil reduces heat rejection and causes high condensing pressure,
which results in elevated head pressure.
6. A refrigeration system with a thermostatic expansion valve (TXV) is operating with very
high superheat. Which of the following is the most likely explanation?
A. The evaporator is being overfed
B. The metering device may be restricted or underfeeding
C. The condenser is flooded with refrigerant
D. The compressor valves are sealing perfectly
Answer: B
Rationale: High superheat often means the evaporator is being starved, commonly caused by a
restricted TXV, low refrigerant charge, or liquid line restriction.
7. Which HVAC electrical component is designed to open a circuit automatically when motor
current exceeds a safe operating limit for too long?
, Page 4 of 63
A. Contactor
B. Overload protector
C. Transformer
D. Pressure switch
Answer: B
Rationale: An overload protector protects motors from overheating and damage caused by
excessive current draw over time.
8. If an evaporator coil becomes heavily iced during operation, which of the following should
be checked first because it is one of the most common causes?
A. Condenser fan blade pitch
B. Return and supply airflow conditions
C. Liquid line diameter
D. Compressor crankcase heater wattage
Answer: B
Rationale: One of the most common causes of evaporator icing is poor airflow, often from dirty
filters, blower problems, or blocked ducts.
9. In basic electrical theory, Ohm’s law is correctly expressed by which relationship?
A. Watts = Volts × Ohms
B. Volts = Amps × Ohms
C. Amps = Volts × Watts
D. Resistance = Watts × Current
Answer: B
Rationale: Ohm’s law states V = I × R, where voltage equals current multiplied by resistance.
10. A compressor that repeatedly starts and stops at short intervals without satisfying the
thermostat is experiencing which condition?
A. Equalized loading
B. Short cycling
C. Deep vacuum operation
D. Positive displacement balancing
Louisiana New Orleans Second Class Stationary Air
Conditioning EXAM QUESTIONS AND CORRECT VERIFIED
SOLUTIONS LATEST UPDATE THIS YEAR – JUST RELEASED
Louisiana New Orleans Second Class Stationary Air Conditioning - 640-LA Contractor Exam
BRIEF EXAM COVERAGE
This exam typically focuses on the practical and technical knowledge needed for stationary air
conditioning systems, basic refrigeration principles, HVAC electrical controls, motors,
compressors, air distribution, piping, maintenance, safety, troubleshooting, and code-related
operational practices.
Main content areas likely covered:
• Refrigeration cycle fundamentals
• Air conditioning system components
• Compressors, condensers, evaporators, metering devices
• Refrigerants and refrigerant handling
• Superheat and subcooling
• Electrical theory and HVAC controls
• Motors, starters, relays, contactors, overloads
• Thermostats and control circuits
• Airflow, duct systems, static pressure, psychrometrics basics
• Chilled water and piping concepts
• Pumps, valves, expansion tanks
Questions 1–50
, Page 2 of 63
1. In a standard vapor-compression air conditioning system, which component is primarily
responsible for raising the pressure and temperature of the refrigerant vapor before it enters
the condenser?
A. Evaporator
B. Metering device
C. Compressor
D. Receiver
Answer: C
Rationale: The compressor raises the refrigerant vapor from low-pressure, low-temperature
vapor to high-pressure, high-temperature vapor, allowing it to reject heat in the condenser.
2. A technician observes frost forming on the suction line near the evaporator and notices
poor cooling performance. Which condition is the most likely cause of this symptom?
A. Excessive airflow across the evaporator
B. Restricted airflow or low evaporator load
C. High condenser fan speed
D. Excessive subcooling only
Answer: B
Rationale: Frost on the suction line often indicates low evaporator temperature, usually caused
by restricted airflow, dirty filters, dirty evaporator coils, or low load conditions.
3. Which electrical instrument is most appropriate for measuring current draw on a running
compressor without disconnecting the circuit conductors?
A. Ohmmeter
B. Clamp ammeter
C. Megohmmeter
D. Continuity tester
Answer: B
Rationale: A clamp ammeter allows current measurement by clamping around a conductor
without opening the circuit, making it ideal for measuring running compressor amperage.
, Page 3 of 63
4. In an air conditioning system, the primary purpose of the condenser is to perform which of
the following functions?
A. Increase superheat
B. Reject heat from the refrigerant to the outside medium
C. Reduce blower speed
D. Increase refrigerant velocity only
Answer: B
Rationale: The condenser rejects heat absorbed from the conditioned space plus the heat of
compression to the surrounding air or water.
5. Which condition is most likely to cause abnormally high head pressure in an air-cooled
condensing unit during normal operating conditions?
A. Dirty condenser coil
B. Low evaporator load only
C. Weak blower motor capacitor
D. Oversized return duct
Answer: A
Rationale: A dirty condenser coil reduces heat rejection and causes high condensing pressure,
which results in elevated head pressure.
6. A refrigeration system with a thermostatic expansion valve (TXV) is operating with very
high superheat. Which of the following is the most likely explanation?
A. The evaporator is being overfed
B. The metering device may be restricted or underfeeding
C. The condenser is flooded with refrigerant
D. The compressor valves are sealing perfectly
Answer: B
Rationale: High superheat often means the evaporator is being starved, commonly caused by a
restricted TXV, low refrigerant charge, or liquid line restriction.
7. Which HVAC electrical component is designed to open a circuit automatically when motor
current exceeds a safe operating limit for too long?
, Page 4 of 63
A. Contactor
B. Overload protector
C. Transformer
D. Pressure switch
Answer: B
Rationale: An overload protector protects motors from overheating and damage caused by
excessive current draw over time.
8. If an evaporator coil becomes heavily iced during operation, which of the following should
be checked first because it is one of the most common causes?
A. Condenser fan blade pitch
B. Return and supply airflow conditions
C. Liquid line diameter
D. Compressor crankcase heater wattage
Answer: B
Rationale: One of the most common causes of evaporator icing is poor airflow, often from dirty
filters, blower problems, or blocked ducts.
9. In basic electrical theory, Ohm’s law is correctly expressed by which relationship?
A. Watts = Volts × Ohms
B. Volts = Amps × Ohms
C. Amps = Volts × Watts
D. Resistance = Watts × Current
Answer: B
Rationale: Ohm’s law states V = I × R, where voltage equals current multiplied by resistance.
10. A compressor that repeatedly starts and stops at short intervals without satisfying the
thermostat is experiencing which condition?
A. Equalized loading
B. Short cycling
C. Deep vacuum operation
D. Positive displacement balancing
