HVAC S.T.A.R Questions and Answers
| Latest Version | 2025/2026 | Correct &
Verified
What is latent heat in HVAC systems?
✔✔Energy absorbed or released during a change in moisture content.
What is sensible heat?
✔✔Energy that changes temperature without changing moisture content.
Why is a pressure-temperature chart used?
✔✔To determine refrigerant conditions and system performance.
What is a variable-speed blower motor used for?
✔✔To adjust airflow according to load for comfort and efficiency.
Why is refrigerant line sizing important?
✔✔To maintain proper pressure and system efficiency.
What is the purpose of a condensate pump?
✔✔To remove condensate where gravity drainage is insufficient.
Why should HVAC technicians check for refrigerant leaks?
1
,✔✔To prevent system inefficiency and environmental harm.
What is the role of an expansion valve?
✔✔To control refrigerant flow into the evaporator coil.
What is the main function of an air filter in an HVAC system?
✔✔To remove dust, debris, and contaminants from the air.
Why is proper refrigerant charge critical for AC efficiency?
✔✔It ensures optimal cooling and prevents system damage.
What is the purpose of a condenser coil?
✔✔To release heat from refrigerant to the outdoor environment.
Why do evaporator coils freeze in some systems?
✔✔Low airflow or insufficient refrigerant can cause freezing.
What does a two-stage compressor do in a heat pump?
✔✔Provides high and low cooling capacity for efficiency and comfort.
Why should HVAC technicians check voltage before servicing equipment?
✔✔To ensure safety and prevent electrical damage.
2
,What is the role of a metering device in refrigeration?
✔✔To control refrigerant flow into the evaporator coil.
Why is duct sealing important for system performance?
✔✔To prevent air leaks and maintain efficiency.
What does SEER measure?
✔✔Cooling efficiency of air conditioners over a season.
What is the purpose of a blower motor?
✔✔To circulate air through the HVAC system.
Why is a refrigerant recovery machine used?
✔✔To safely remove refrigerant before servicing or disposal.
What is a common cause of high head pressure in an AC system?
✔✔Dirty condenser coils or restricted airflow.
Why is grounding essential in HVAC electrical systems?
✔✔To protect people and equipment from electrical hazards.
3
, What is the function of a thermostat?
✔✔To sense temperature and control heating or cooling equipment.
Why do HVAC systems require regular maintenance?
✔✔To improve efficiency, reliability, and equipment lifespan.
What is superheat in an air conditioning system?
✔✔The temperature of refrigerant vapor above its boiling point.
What is subcooling in refrigeration systems?
✔✔The temperature of liquid refrigerant below its condensing point.
Why is airflow measurement important in ductwork?
✔✔To ensure proper distribution of conditioned air.
What is the purpose of a heat exchanger?
✔✔To transfer heat from combustion gases to air safely.
Why are condensate drains important?
✔✔To remove moisture and prevent water damage.
What does a sight glass in refrigeration systems indicate?
4
| Latest Version | 2025/2026 | Correct &
Verified
What is latent heat in HVAC systems?
✔✔Energy absorbed or released during a change in moisture content.
What is sensible heat?
✔✔Energy that changes temperature without changing moisture content.
Why is a pressure-temperature chart used?
✔✔To determine refrigerant conditions and system performance.
What is a variable-speed blower motor used for?
✔✔To adjust airflow according to load for comfort and efficiency.
Why is refrigerant line sizing important?
✔✔To maintain proper pressure and system efficiency.
What is the purpose of a condensate pump?
✔✔To remove condensate where gravity drainage is insufficient.
Why should HVAC technicians check for refrigerant leaks?
1
,✔✔To prevent system inefficiency and environmental harm.
What is the role of an expansion valve?
✔✔To control refrigerant flow into the evaporator coil.
What is the main function of an air filter in an HVAC system?
✔✔To remove dust, debris, and contaminants from the air.
Why is proper refrigerant charge critical for AC efficiency?
✔✔It ensures optimal cooling and prevents system damage.
What is the purpose of a condenser coil?
✔✔To release heat from refrigerant to the outdoor environment.
Why do evaporator coils freeze in some systems?
✔✔Low airflow or insufficient refrigerant can cause freezing.
What does a two-stage compressor do in a heat pump?
✔✔Provides high and low cooling capacity for efficiency and comfort.
Why should HVAC technicians check voltage before servicing equipment?
✔✔To ensure safety and prevent electrical damage.
2
,What is the role of a metering device in refrigeration?
✔✔To control refrigerant flow into the evaporator coil.
Why is duct sealing important for system performance?
✔✔To prevent air leaks and maintain efficiency.
What does SEER measure?
✔✔Cooling efficiency of air conditioners over a season.
What is the purpose of a blower motor?
✔✔To circulate air through the HVAC system.
Why is a refrigerant recovery machine used?
✔✔To safely remove refrigerant before servicing or disposal.
What is a common cause of high head pressure in an AC system?
✔✔Dirty condenser coils or restricted airflow.
Why is grounding essential in HVAC electrical systems?
✔✔To protect people and equipment from electrical hazards.
3
, What is the function of a thermostat?
✔✔To sense temperature and control heating or cooling equipment.
Why do HVAC systems require regular maintenance?
✔✔To improve efficiency, reliability, and equipment lifespan.
What is superheat in an air conditioning system?
✔✔The temperature of refrigerant vapor above its boiling point.
What is subcooling in refrigeration systems?
✔✔The temperature of liquid refrigerant below its condensing point.
Why is airflow measurement important in ductwork?
✔✔To ensure proper distribution of conditioned air.
What is the purpose of a heat exchanger?
✔✔To transfer heat from combustion gases to air safely.
Why are condensate drains important?
✔✔To remove moisture and prevent water damage.
What does a sight glass in refrigeration systems indicate?
4
