Louisiana (New Orleans) Second Class Stationary Air Conditioning – 640-LA Contractor Exam Questions and Answers | PDF

Louisiana (New Orleans) Second Class Stationary Air
Conditioning – 640-LA Contractor Exam Questions
and Answers | PDF
Purpose:
This exam is designed to prepare candidates for the Louisiana 640-LA Second Class
Stationary Air Conditioning Contractor License. It covers theoretical knowledge, system
operation, maintenance, and safety standards required to pass the official state exam.

 Answer Format: Correct answer in bold, with brief explanation in italics

Content Overview:

 Refrigeration Cycle: Compressor, condenser, expansion valve, evaporator
 Heat Pumps: Reversing valves, heating and cooling modes
 Electrical Components: Contactors, relays, fuses, breakers, motors
 Refrigerants & Oils: R-22, R-410A, mineral oil, POE oil
 System Testing & Diagnostics: Pressure readings, superheat/subcooling, airflow
measurement
 Safety & Standards: EPA 608, high/low pressure protection, short-cycling prevention
 Maintenance & Efficiency: Coil cleaning, filter replacement, airflow management
 Tools & Instruments: Manifold gauges, vacuum pumps, anemometers, clamp-on
ammeters, leak detectors




Question 1
Which component in a refrigeration system compresses the refrigerant and
raises its pressure?
A. Condenser
B. Evaporator
C. Compressor
D. Expansion valve

Answer: C
The compressor compresses the refrigerant, increasing its pressure and
temperature.

,Question 2
What is the main purpose of the condenser in an air conditioning system?
A. Absorb heat from indoor air
B. Reject heat to the outside environment
C. Reduce refrigerant pressure
D. Control airflow

Answer: B
The condenser removes heat from the high-pressure refrigerant and transfers it
to the outside air or water.



Question 3
Which device regulates the flow of refrigerant into the evaporator?
A. Compressor
B. Condenser
C. Expansion valve
D. Fan coil unit

Answer: C
The expansion valve meters refrigerant to the evaporator, maintaining proper
pressure and temperature.



Question 4
What is superheat in a refrigeration system?
A. Temperature of refrigerant in condenser
B. Temperature of refrigerant vapor above its saturation temperature at a
given pressure
C. Pressure of refrigerant in compressor
D. Heat absorbed by air

,Answer: B
Superheat ensures the refrigerant is fully vaporized before entering the
compressor.



Question 5
Which refrigerant type is commonly used in modern stationary AC systems in
Louisiana?
A. R-12
B. R-410A
C. R-22
D. Ammonia

Answer: B
R-410A is widely used in new residential and commercial systems due to its
efficiency and compliance with regulations.



Question 6
Which safety device prevents excessive pressure in a refrigeration system?
A. Thermostat
B. Expansion valve
C. Pressure relief valve
D. Solenoid valve

Answer: C
A pressure relief valve opens to release refrigerant when pressure exceeds safe
limits.



Question 7
What type of compressor is most common in small commercial AC units?
A. Reciprocating
B. Screw

, C. Centrifugal
D. Scroll

Answer: D
Scroll compressors are efficient, quiet, and commonly used in smaller
commercial units.



Question 8
Which component in a split system absorbs heat from indoor air?
A. Compressor
B. Condenser
C. Evaporator coil
D. Expansion valve

Answer: C
The evaporator coil absorbs heat from indoor air and vaporizes the refrigerant.



Question 9
Which electrical device protects a compressor motor from overload?
A. Transformer
B. Motor overload protector
C. Circuit breaker
D. Contactor

Answer: B
Motor overload protectors prevent motor damage due to excessive current.



Question 10
What does the SEER rating measure?
A. Refrigerant type
B. Airflow velocity