640-LA SecondClass Stationary Air
Conditioning Contractor Exam 2026 with
verified answers
Section 1: Theory, Terminology, and General Requirements
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
Rationale: Sensible heat is the heat added or removed that changes the temperature of a
substance but does not cause a phase change. Option A describes latent heat.
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
Rationale: Latent heat is the energy absorbed or released during a phase change (e.g., liquid
to vapor) without a change in temperature. This is critical for dehumidification.
3. 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
Rationale: The second law of thermodynamics states that heat transfer occurs
spontaneously from a region of higher temperature to a region of lower temperature.
4. 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
Rationale: Air conditioning's primary purpose is to maintain a comfortable and safe indoor
environment by controlling temperature, humidity, and air quality.
5. The term "BTU" stands for:
A) British Thermal Unit
B) Boiler Temperature Unit
C) Basic Temperature Utility
D) Burn Time Unit
Answer: A
Rationale: BTU is short for "British Thermal Unit," the 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.
6. 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
Rationale: ASHRAE is a global professional organization that publishes standards and
guidelines for HVAC/R systems, including the widely used refrigerant safety classifications.
7. The psychrometric chart is primarily used to analyze:
A) Electrical conductivity of refrigerants
B) The relationship between air temperature, moisture, and enthalpy
C) Efficiency of compressors at varying pressures
D) Fan performance curves
Answer: B
Rationale: A psychrometric chart is a graphical tool that helps HVAC professionals
understand and visualize the properties of air, including dry-bulb temperature, wet-bulb
temperature, humidity, and enthalpy.
8. 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
Rationale: Internal loads are heat sources originating inside the building, such as people,
lighting, and machinery. Solar heat gain and infiltration are considered external loads.
Section 2: Compressors and Types of Systems
9. What is the primary function of the compressor in a refrigeration cycle?
A) To absorb heat from the indoor air
B) To compress the refrigerant and increase its pressure and temperature
C) To reject heat to the outdoor environment
D) To expand the refrigerant before it enters the evaporator
, Answer: B
Rationale: The compressor acts as the pump of the system. It takes in low-pressure, low-
temperature refrigerant vapor and compresses it, raising its pressure and temperature so it
can release heat in the condenser.
10. Which type of compressor is most suitable for large commercial air conditioning
systems due to its high efficiency at variable loads?
A) Reciprocating compressor
B) Scroll compressor
C) Screw compressor
D) Centrifugal compressor
Answer: D
Rationale: Centrifugal compressors are ideal for large commercial and industrial
applications. They are highly efficient at moving large volumes of refrigerant and perform
well under variable load conditions.
11. In a split system air conditioner, where is the compressor typically located?
A) Inside the indoor air handling unit
B) In the outdoor condenser unit
C) Within the ductwork
D) Inside the building's mechanical room
Answer: B
Rationale: In a split system, the compressor is housed in the outdoor unit (condenser) to
isolate the noise of operation and to facilitate the rejection of heat to the outdoors.
12. What type of compressor is known for its simplicity and widespread use in small to
medium-sized air conditioning systems?
A) Centrifugal compressor
B) Scroll compressor
C) Reciprocating compressor
D) Screw compressor
Conditioning Contractor Exam 2026 with
verified answers
Section 1: Theory, Terminology, and General Requirements
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
Rationale: Sensible heat is the heat added or removed that changes the temperature of a
substance but does not cause a phase change. Option A describes latent heat.
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
Rationale: Latent heat is the energy absorbed or released during a phase change (e.g., liquid
to vapor) without a change in temperature. This is critical for dehumidification.
3. 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
Rationale: The second law of thermodynamics states that heat transfer occurs
spontaneously from a region of higher temperature to a region of lower temperature.
4. 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
Rationale: Air conditioning's primary purpose is to maintain a comfortable and safe indoor
environment by controlling temperature, humidity, and air quality.
5. The term "BTU" stands for:
A) British Thermal Unit
B) Boiler Temperature Unit
C) Basic Temperature Utility
D) Burn Time Unit
Answer: A
Rationale: BTU is short for "British Thermal Unit," the 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.
6. 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
Rationale: ASHRAE is a global professional organization that publishes standards and
guidelines for HVAC/R systems, including the widely used refrigerant safety classifications.
7. The psychrometric chart is primarily used to analyze:
A) Electrical conductivity of refrigerants
B) The relationship between air temperature, moisture, and enthalpy
C) Efficiency of compressors at varying pressures
D) Fan performance curves
Answer: B
Rationale: A psychrometric chart is a graphical tool that helps HVAC professionals
understand and visualize the properties of air, including dry-bulb temperature, wet-bulb
temperature, humidity, and enthalpy.
8. 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
Rationale: Internal loads are heat sources originating inside the building, such as people,
lighting, and machinery. Solar heat gain and infiltration are considered external loads.
Section 2: Compressors and Types of Systems
9. What is the primary function of the compressor in a refrigeration cycle?
A) To absorb heat from the indoor air
B) To compress the refrigerant and increase its pressure and temperature
C) To reject heat to the outdoor environment
D) To expand the refrigerant before it enters the evaporator
, Answer: B
Rationale: The compressor acts as the pump of the system. It takes in low-pressure, low-
temperature refrigerant vapor and compresses it, raising its pressure and temperature so it
can release heat in the condenser.
10. Which type of compressor is most suitable for large commercial air conditioning
systems due to its high efficiency at variable loads?
A) Reciprocating compressor
B) Scroll compressor
C) Screw compressor
D) Centrifugal compressor
Answer: D
Rationale: Centrifugal compressors are ideal for large commercial and industrial
applications. They are highly efficient at moving large volumes of refrigerant and perform
well under variable load conditions.
11. In a split system air conditioner, where is the compressor typically located?
A) Inside the indoor air handling unit
B) In the outdoor condenser unit
C) Within the ductwork
D) Inside the building's mechanical room
Answer: B
Rationale: In a split system, the compressor is housed in the outdoor unit (condenser) to
isolate the noise of operation and to facilitate the rejection of heat to the outdoors.
12. What type of compressor is known for its simplicity and widespread use in small to
medium-sized air conditioning systems?
A) Centrifugal compressor
B) Scroll compressor
C) Reciprocating compressor
D) Screw compressor
