STAR HVAC Mastery Exam Questions and Answers Plus
Rationales
1. What is the primary purpose of a heat exchanger in an HVAC
system?
To transfer heat between two mediums without mixing them
The heat exchanger allows heat transfer from one fluid to another
while keeping them separate, ensuring efficient heating or cooling.
2. Which type of refrigerant has zero ozone depletion potential?
R-410A
R-410A is a hydrofluorocarbon (HFC) with no ozone depletion
potential, making it environmentally safer than older CFCs.
3. What does the term "superheat" refer to in a refrigeration
system?
The temperature of refrigerant vapor above its saturation
temperature
Superheat measures how much the refrigerant vapor has been
heated beyond its boiling point, ensuring the evaporator is fully
utilized.
4. What is the main advantage of a variable speed blower in an HVAC
system?
Improved energy efficiency and comfort
Variable speed blowers adjust airflow to match load requirements,
reducing energy use and providing more consistent temperatures.
5. Which component of an HVAC system removes moisture from the
air?
, The evaporator coil
As air passes over the cold evaporator coil, moisture condenses,
reducing humidity.
6. What is the typical purpose of a thermostatic expansion valve
(TXV)?
To regulate refrigerant flow into the evaporator
The TXV ensures the evaporator receives the correct amount of
refrigerant, optimizing performance and preventing flooding.
7. In a split-system air conditioner, where is the compressor usually
located?
In the outdoor unit
The outdoor unit houses the compressor and condenser coil, while
the indoor unit contains the evaporator coil and blower.
8. What type of filter is most effective at removing small airborne
particles?
HEPA filter
HEPA filters can remove particles as small as 0.3 microns, making
them highly effective for indoor air quality.
9. Which of the following is a sign of low refrigerant charge in an AC
system?
Ice formation on the evaporator coil
Low refrigerant reduces heat absorption, causing the coil to freeze
and reducing system efficiency.
10. What does SEER stand for in air conditioning systems?
Seasonal Energy Efficiency Ratio
SEER measures an AC unit’s cooling efficiency over a typical
cooling season, helping compare energy performance.
,11. What is the purpose of an air handler in an HVAC system?
To circulate conditioned air throughout the building
The air handler contains a blower, coil, and filters to move air
through ductwork and maintain desired temperatures.
12. Which refrigerant is commonly used in residential HVAC
systems today?
R-410A
R-410A replaced older CFC and HCFC refrigerants due to lower
ozone depletion and better energy efficiency.
13. What is the standard voltage for residential HVAC systems in
the U.S.?
240 volts
Most residential HVAC systems use 240V for compressors and
120V for controls or small components.
14. What does a condenser coil do in an air conditioning
system?
Releases heat from the refrigerant to the outside air
The condenser coil allows the refrigerant to expel absorbed heat,
converting vapor back to liquid.
15. What is the main purpose of duct insulation?
To reduce heat loss or gain in the air distribution system
Insulated ducts maintain temperature efficiency and prevent
energy waste.
16. Which type of HVAC system provides both heating and
cooling?
Split system
, Split systems can provide air conditioning and heating through a
combination of indoor and outdoor units.
17. What does a blower motor do?
Moves air through the ductwork
The blower ensures proper circulation of conditioned air,
maintaining comfort and system efficiency.
18. Which of the following is a common cause of compressor
failure?
Low refrigerant levels
Low refrigerant can cause overheating, inadequate lubrication,
and mechanical stress on the compressor.
19. In an HVAC system, what is the purpose of a filter drier?
To remove moisture and contaminants from the refrigerant
Filter driers protect system components from corrosion, debris,
and ice formation caused by moisture.
20. What type of HVAC system is most suitable for large
commercial buildings?
Chilled water system
Chilled water systems use centralized cooling and pumping,
making them ideal for large-scale applications.
21. Which component controls the flow of air in a ducted HVAC
system?
Dampers
Dampers can be manual or automatic and regulate airflow to
different zones or rooms.
Rationales
1. What is the primary purpose of a heat exchanger in an HVAC
system?
To transfer heat between two mediums without mixing them
The heat exchanger allows heat transfer from one fluid to another
while keeping them separate, ensuring efficient heating or cooling.
2. Which type of refrigerant has zero ozone depletion potential?
R-410A
R-410A is a hydrofluorocarbon (HFC) with no ozone depletion
potential, making it environmentally safer than older CFCs.
3. What does the term "superheat" refer to in a refrigeration
system?
The temperature of refrigerant vapor above its saturation
temperature
Superheat measures how much the refrigerant vapor has been
heated beyond its boiling point, ensuring the evaporator is fully
utilized.
4. What is the main advantage of a variable speed blower in an HVAC
system?
Improved energy efficiency and comfort
Variable speed blowers adjust airflow to match load requirements,
reducing energy use and providing more consistent temperatures.
5. Which component of an HVAC system removes moisture from the
air?
, The evaporator coil
As air passes over the cold evaporator coil, moisture condenses,
reducing humidity.
6. What is the typical purpose of a thermostatic expansion valve
(TXV)?
To regulate refrigerant flow into the evaporator
The TXV ensures the evaporator receives the correct amount of
refrigerant, optimizing performance and preventing flooding.
7. In a split-system air conditioner, where is the compressor usually
located?
In the outdoor unit
The outdoor unit houses the compressor and condenser coil, while
the indoor unit contains the evaporator coil and blower.
8. What type of filter is most effective at removing small airborne
particles?
HEPA filter
HEPA filters can remove particles as small as 0.3 microns, making
them highly effective for indoor air quality.
9. Which of the following is a sign of low refrigerant charge in an AC
system?
Ice formation on the evaporator coil
Low refrigerant reduces heat absorption, causing the coil to freeze
and reducing system efficiency.
10. What does SEER stand for in air conditioning systems?
Seasonal Energy Efficiency Ratio
SEER measures an AC unit’s cooling efficiency over a typical
cooling season, helping compare energy performance.
,11. What is the purpose of an air handler in an HVAC system?
To circulate conditioned air throughout the building
The air handler contains a blower, coil, and filters to move air
through ductwork and maintain desired temperatures.
12. Which refrigerant is commonly used in residential HVAC
systems today?
R-410A
R-410A replaced older CFC and HCFC refrigerants due to lower
ozone depletion and better energy efficiency.
13. What is the standard voltage for residential HVAC systems in
the U.S.?
240 volts
Most residential HVAC systems use 240V for compressors and
120V for controls or small components.
14. What does a condenser coil do in an air conditioning
system?
Releases heat from the refrigerant to the outside air
The condenser coil allows the refrigerant to expel absorbed heat,
converting vapor back to liquid.
15. What is the main purpose of duct insulation?
To reduce heat loss or gain in the air distribution system
Insulated ducts maintain temperature efficiency and prevent
energy waste.
16. Which type of HVAC system provides both heating and
cooling?
Split system
, Split systems can provide air conditioning and heating through a
combination of indoor and outdoor units.
17. What does a blower motor do?
Moves air through the ductwork
The blower ensures proper circulation of conditioned air,
maintaining comfort and system efficiency.
18. Which of the following is a common cause of compressor
failure?
Low refrigerant levels
Low refrigerant can cause overheating, inadequate lubrication,
and mechanical stress on the compressor.
19. In an HVAC system, what is the purpose of a filter drier?
To remove moisture and contaminants from the refrigerant
Filter driers protect system components from corrosion, debris,
and ice formation caused by moisture.
20. What type of HVAC system is most suitable for large
commercial buildings?
Chilled water system
Chilled water systems use centralized cooling and pumping,
making them ideal for large-scale applications.
21. Which component controls the flow of air in a ducted HVAC
system?
Dampers
Dampers can be manual or automatic and regulate airflow to
different zones or rooms.
