Louisiana (New Orleans) Second Class Stationary Air
Conditioning - 640-LA Contractor Exam
Practice Test
Section 1: Theory, Terminology, and General Requirements (10%)
1. Which of the following best describes "sensible heat" in an air conditioning context?
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
Answer: b) The heat associated with a change in temperature of a substance without a
phase change
Rationale: Sensible heat is the heat added or removed that changes the temperature of a
substance but does not cause a phase change. Latent heat, in contrast, causes a phase
change without a temperature change .
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
Answer: b) Heat required to induce a phase change without a temperature change
Rationale: Latent heat is the energy absorbed or released during a phase change, such as
evaporation or condensation, without a change in temperature. In air conditioning, this
typically refers to moisture removal .
3. The primary goal of an air conditioning system is to:
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
Answer: b) Control temperature, humidity, and indoor air quality
Rationale: Air conditioning's primary purpose is to control temperature, humidity, and air
quality to maintain a comfortable and safe indoor environment .
4. The term "BTU" stands for:
a) British Thermal Unit
b) Boiler Temperature Unit
c) Basic Temperature Utility
d) Burn Time Unit
Answer: a) British Thermal Unit
Rationale: BTU is short for "British Thermal Unit," a standard measure of heat energy. One
BTU is the amount of heat needed to raise the temperature of one pound of water by 1°F .
5. According to basic thermodynamic principles, heat naturally flows:
a) From cold objects to warmer objects
b) From warm objects to colder objects
c) Randomly in all directions
d) Only if driven by a compressor
Answer: b) From warm objects to colder objects
Rationale: The second law of thermodynamics states that heat transfer occurs
spontaneously from a region of higher temperature to a region of lower temperature .
6. What is the most common type of heat transfer method in an air-cooled condenser?
a) Conduction
b) Convection
c) Radiation
d) Sublimation
,Answer: b) Convection
Rationale: Air-cooled condensers primarily use forced or natural convection to transfer heat
from the refrigerant inside the coils to the ambient air moving across the coil surface .
7. In HVAC terminology, "ASHRAE" stands for:
a) American Society of Heating, Refrigerating and Air-Conditioning Engineers
b) Association of Systemic Heating and Refrigeration Engineers
c) American Service for Heat and Refrigeration Evaluation
d) Accredited Society of Home Air Regulation Experts
Answer: a) American Society of Heating, Refrigerating and Air-Conditioning Engineers
Rationale: ASHRAE is a global professional society that advances human well-being through
sustainable technology for the built environment, focusing on HVAC/R systems and
standards .
8. The psychrometric chart is primarily used to analyze:
a) Electrical conductivity of refrigerants
b) Relationship between air temperature, moisture, and enthalpy
c) Efficiency of compressors in varying pressures
d) Fan performance curves
Answer: b) Relationship between air temperature, moisture, and enthalpy
Rationale: A psychrometric chart is a graphical representation of the properties of moist air.
It helps HVAC professionals understand air properties (dry-bulb temperature, wet-bulb
temperature, relative humidity, dew point, and enthalpy) to design and analyze systems .
9. When referring to air conditioning loads, which of the following is considered an internal
load?
a) Solar heat gain through windows
b) Heat gain from occupants and appliances
c) Heat loss through exterior walls
d) Infiltration from outside air
, Answer: b) Heat gain from occupants and appliances
Rationale: Internal loads include heat sources originating inside the building, such as people,
lights, computers, and other equipment. The air conditioning system must remove this heat .
10. In Louisiana, local amendments to the International Mechanical Code (IMC) may require
additional considerations for:
a) Seismic anchoring
b) Flood protection and elevated equipment platforms
c) High-altitude condenser sizing
d) Sub-zero pipe insulation
Answer: b) Flood protection and elevated equipment platforms
Rationale: Given New Orleans' unique geography and flood risks, local amendments to the
IMC often include stricter requirements for flood protection, such as elevating outdoor
equipment and securing mechanical systems against water damage .
11. What is the term for the temperature at which moisture in the air begins to condense on
a surface?
a) Wet-bulb temperature
b) Sensible temperature
c) Dry-bulb temperature
d) Dew point temperature
Answer: d) Dew point temperature
Rationale: The dew point is the temperature at which the air becomes fully saturated with
water vapor. If the air is cooled below this point, or if it comes into contact with a surface
below this temperature, water vapor will begin to condense .
12. What does the term "short cycling" refer to in air conditioning systems?
a) The compressor running continuously
b) The system rapidly turning on and off
c) Slow refrigerant flow
d) Inefficient duct design
Conditioning - 640-LA Contractor Exam
Practice Test
Section 1: Theory, Terminology, and General Requirements (10%)
1. Which of the following best describes "sensible heat" in an air conditioning context?
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
Answer: b) The heat associated with a change in temperature of a substance without a
phase change
Rationale: Sensible heat is the heat added or removed that changes the temperature of a
substance but does not cause a phase change. Latent heat, in contrast, causes a phase
change without a temperature change .
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
Answer: b) Heat required to induce a phase change without a temperature change
Rationale: Latent heat is the energy absorbed or released during a phase change, such as
evaporation or condensation, without a change in temperature. In air conditioning, this
typically refers to moisture removal .
3. The primary goal of an air conditioning system is to:
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
Answer: b) Control temperature, humidity, and indoor air quality
Rationale: Air conditioning's primary purpose is to control temperature, humidity, and air
quality to maintain a comfortable and safe indoor environment .
4. The term "BTU" stands for:
a) British Thermal Unit
b) Boiler Temperature Unit
c) Basic Temperature Utility
d) Burn Time Unit
Answer: a) British Thermal Unit
Rationale: BTU is short for "British Thermal Unit," a standard measure of heat energy. One
BTU is the amount of heat needed to raise the temperature of one pound of water by 1°F .
5. According to basic thermodynamic principles, heat naturally flows:
a) From cold objects to warmer objects
b) From warm objects to colder objects
c) Randomly in all directions
d) Only if driven by a compressor
Answer: b) From warm objects to colder objects
Rationale: The second law of thermodynamics states that heat transfer occurs
spontaneously from a region of higher temperature to a region of lower temperature .
6. What is the most common type of heat transfer method in an air-cooled condenser?
a) Conduction
b) Convection
c) Radiation
d) Sublimation
,Answer: b) Convection
Rationale: Air-cooled condensers primarily use forced or natural convection to transfer heat
from the refrigerant inside the coils to the ambient air moving across the coil surface .
7. In HVAC terminology, "ASHRAE" stands for:
a) American Society of Heating, Refrigerating and Air-Conditioning Engineers
b) Association of Systemic Heating and Refrigeration Engineers
c) American Service for Heat and Refrigeration Evaluation
d) Accredited Society of Home Air Regulation Experts
Answer: a) American Society of Heating, Refrigerating and Air-Conditioning Engineers
Rationale: ASHRAE is a global professional society that advances human well-being through
sustainable technology for the built environment, focusing on HVAC/R systems and
standards .
8. The psychrometric chart is primarily used to analyze:
a) Electrical conductivity of refrigerants
b) Relationship between air temperature, moisture, and enthalpy
c) Efficiency of compressors in varying pressures
d) Fan performance curves
Answer: b) Relationship between air temperature, moisture, and enthalpy
Rationale: A psychrometric chart is a graphical representation of the properties of moist air.
It helps HVAC professionals understand air properties (dry-bulb temperature, wet-bulb
temperature, relative humidity, dew point, and enthalpy) to design and analyze systems .
9. When referring to air conditioning loads, which of the following is considered an internal
load?
a) Solar heat gain through windows
b) Heat gain from occupants and appliances
c) Heat loss through exterior walls
d) Infiltration from outside air
, Answer: b) Heat gain from occupants and appliances
Rationale: Internal loads include heat sources originating inside the building, such as people,
lights, computers, and other equipment. The air conditioning system must remove this heat .
10. In Louisiana, local amendments to the International Mechanical Code (IMC) may require
additional considerations for:
a) Seismic anchoring
b) Flood protection and elevated equipment platforms
c) High-altitude condenser sizing
d) Sub-zero pipe insulation
Answer: b) Flood protection and elevated equipment platforms
Rationale: Given New Orleans' unique geography and flood risks, local amendments to the
IMC often include stricter requirements for flood protection, such as elevating outdoor
equipment and securing mechanical systems against water damage .
11. What is the term for the temperature at which moisture in the air begins to condense on
a surface?
a) Wet-bulb temperature
b) Sensible temperature
c) Dry-bulb temperature
d) Dew point temperature
Answer: d) Dew point temperature
Rationale: The dew point is the temperature at which the air becomes fully saturated with
water vapor. If the air is cooled below this point, or if it comes into contact with a surface
below this temperature, water vapor will begin to condense .
12. What does the term "short cycling" refer to in air conditioning systems?
a) The compressor running continuously
b) The system rapidly turning on and off
c) Slow refrigerant flow
d) Inefficient duct design
