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Louisiana New Orleans Second Class Stationary Air
Conditioning - 640-LA Contractor Exam ACTUAL EXAM
COMPLETE 400 QUESTIONS AND VERIFIED SOLUTIONS
LATEST UPDATE THIS YEAR
New Orleans Second Class Stationary Air Conditioning - 640-LA Contractor Exam. This
certification is required for individuals operating and maintaining high-tonnage stationary air
conditioning and refrigeration equipment within the jurisdiction of the City of New Orleans.
Exam Overview & Content Areas
The full 640-LA exam (and these practice batches) covers the following critical domains:
1. Thermodynamics & Psychrometrics: Sensible/Latent heat, BTU calculations, and air
properties.
2. The Refrigeration Cycle: Operation of compressors, condensers, evaporators, and
metering devices.
3. System Components: Accumulators, receivers, oil separators, and filter driers.
4. Refrigerants & Safety: EPA 608 regulations, ASHRAE refrigerant safety groups, and leak
detection.
5. Electricity & Controls: Ohm’s Law, motor starters, thermostats, and safety cut-outs.
6. Piping & Installation: Brazing, evacuation (microns), and charging methods.
7. Maintenance & Troubleshooting: Head pressure issues, subcooling/superheat
diagnostics.
8. Local Codes: City of New Orleans mechanical and stationary engineer ordinances.
Batch 1: Questions 1–100 (Fundamentals & Cycle)
1. Which of the following best describes "sensible heat" in an air conditioning context?
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• A) The heat required to change water to vapor
• B) The heat associated with a change in temperature of a substance without a phase
change
• C) The heat associated with moisture in the air
• D) The heat required to cool the refrigerant below saturation temperature
• Correct Answer: B
• Rationale: Sensible heat changes the temperature of a substance. In AC, this is the heat
removed from the air to lower its dry-bulb temperature.
2. In the context of air conditioning, "latent heat" refers to:
• A) Heat that directly raises the temperature of a substance
• B) Heat required to induce a phase change without a temperature change
• C) Additional heat from solar radiation
• D) Heat lost through uninsulated ducts
• Correct Answer: B
• Rationale: Latent heat is "hidden" heat. In cooling, it refers to the energy removed to
condense water vapor into liquid (dehumidification).
3. The primary goal of an air conditioning system is to:
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• A) Provide mechanical ventilation only
• B) Control temperature, humidity, and indoor air quality
• C) Refrigerate food products in large warehouses
• D) Increase ambient noise for better acoustics
• Correct Answer: B
• Rationale: Comfort cooling requires the simultaneous control of temperature (sensible)
and humidity (latent), along with filtration for air quality.
4. One "Ton of Refrigeration" is defined as the heat required to melt 2,000 lbs of ice at 32°F
in:
• A) 1 hour
• B) 12 hours
• C) 24 hours
• D) 1 week
• Correct Answer: C
• Rationale: One ton of refrigeration equals 288,000 BTUs per 24 hours, which averages
to 12,000 BTUs per hour.
5. What is the standard BTU/hr value for a 5-ton air conditioning system?
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• A) 12,000
• B) 36,000
• C) 60,000
• D) 120,000
• Correct Answer: C
• Rationale: $5 \times 12,000 = 60,000$ BTU/hr.
6. Which component in the refrigeration cycle is considered the "divide" between the high-
pressure and low-pressure sides?
• A) The Compressor and the Evaporator
• B) The Condenser and the Receiver
• C) The Compressor and the Metering Device
• D) The Evaporator and the Suction Accumulator
• Correct Answer: C
• Rationale: The compressor raises the pressure, and the metering device (TXV/Cap tube)
drops it.
7. In a compression cycle, the refrigerant enters the compressor as a:
Louisiana New Orleans Second Class Stationary Air
Conditioning - 640-LA Contractor Exam ACTUAL EXAM
COMPLETE 400 QUESTIONS AND VERIFIED SOLUTIONS
LATEST UPDATE THIS YEAR
New Orleans Second Class Stationary Air Conditioning - 640-LA Contractor Exam. This
certification is required for individuals operating and maintaining high-tonnage stationary air
conditioning and refrigeration equipment within the jurisdiction of the City of New Orleans.
Exam Overview & Content Areas
The full 640-LA exam (and these practice batches) covers the following critical domains:
1. Thermodynamics & Psychrometrics: Sensible/Latent heat, BTU calculations, and air
properties.
2. The Refrigeration Cycle: Operation of compressors, condensers, evaporators, and
metering devices.
3. System Components: Accumulators, receivers, oil separators, and filter driers.
4. Refrigerants & Safety: EPA 608 regulations, ASHRAE refrigerant safety groups, and leak
detection.
5. Electricity & Controls: Ohm’s Law, motor starters, thermostats, and safety cut-outs.
6. Piping & Installation: Brazing, evacuation (microns), and charging methods.
7. Maintenance & Troubleshooting: Head pressure issues, subcooling/superheat
diagnostics.
8. Local Codes: City of New Orleans mechanical and stationary engineer ordinances.
Batch 1: Questions 1–100 (Fundamentals & Cycle)
1. Which of the following best describes "sensible heat" in an air conditioning context?
,Page 2 of 127
• A) The heat required to change water to vapor
• B) The heat associated with a change in temperature of a substance without a phase
change
• C) The heat associated with moisture in the air
• D) The heat required to cool the refrigerant below saturation temperature
• Correct Answer: B
• Rationale: Sensible heat changes the temperature of a substance. In AC, this is the heat
removed from the air to lower its dry-bulb temperature.
2. In the context of air conditioning, "latent heat" refers to:
• A) Heat that directly raises the temperature of a substance
• B) Heat required to induce a phase change without a temperature change
• C) Additional heat from solar radiation
• D) Heat lost through uninsulated ducts
• Correct Answer: B
• Rationale: Latent heat is "hidden" heat. In cooling, it refers to the energy removed to
condense water vapor into liquid (dehumidification).
3. The primary goal of an air conditioning system is to:
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• A) Provide mechanical ventilation only
• B) Control temperature, humidity, and indoor air quality
• C) Refrigerate food products in large warehouses
• D) Increase ambient noise for better acoustics
• Correct Answer: B
• Rationale: Comfort cooling requires the simultaneous control of temperature (sensible)
and humidity (latent), along with filtration for air quality.
4. One "Ton of Refrigeration" is defined as the heat required to melt 2,000 lbs of ice at 32°F
in:
• A) 1 hour
• B) 12 hours
• C) 24 hours
• D) 1 week
• Correct Answer: C
• Rationale: One ton of refrigeration equals 288,000 BTUs per 24 hours, which averages
to 12,000 BTUs per hour.
5. What is the standard BTU/hr value for a 5-ton air conditioning system?
, Page 4 of 127
• A) 12,000
• B) 36,000
• C) 60,000
• D) 120,000
• Correct Answer: C
• Rationale: $5 \times 12,000 = 60,000$ BTU/hr.
6. Which component in the refrigeration cycle is considered the "divide" between the high-
pressure and low-pressure sides?
• A) The Compressor and the Evaporator
• B) The Condenser and the Receiver
• C) The Compressor and the Metering Device
• D) The Evaporator and the Suction Accumulator
• Correct Answer: C
• Rationale: The compressor raises the pressure, and the metering device (TXV/Cap tube)
drops it.
7. In a compression cycle, the refrigerant enters the compressor as a:
