Delaware Heating Contractor
Examination Practice Exam 2026 | 100+
Questions & Answers with Detailed
Rationales | Complete Delaware
Heating Contractor Licensing Exam
Prep, Study Guide, Test Review &
Qualification Preparation
1. What is the primary purpose of a furnace heat exchanger?
A. Increase blower speed
B. Transfer heat from combustion gases to circulating air without mixing the two
C. Increase gas pressure
D. Reduce thermostat voltage
Answer: Transfer heat from combustion gases to circulating air without mixing
the two
Rationale: The heat exchanger transfers combustion heat to the air stream
while keeping combustion products separated from conditioned air.
2. Which component normally controls the temperature setting in a
conventional heating system?
,A. Limit switch
B. Flame sensor
C. Thermostat
D. Gas valve
Answer: Thermostat
Rationale: The thermostat senses space temperature and calls for heat when the
temperature falls below its set point.
3. What is the purpose of a furnace limit control?
A. Increase fuel pressure
B. Prevent excessive furnace temperature
C. Increase blower voltage
D. Control outdoor humidity
Answer: Prevent excessive furnace temperature
Rationale: A high-limit control shuts down or interrupts burner operation when
furnace temperature becomes unsafe.
4. Which fuel is commonly used in residential heating systems?
A. Oxygen
B. Nitrogen
C. Natural gas
D. Carbon dioxide
Answer: Natural gas
Rationale: Natural gas is a common residential heating fuel and is widely used
in furnaces, boilers, and other heating appliances.
5. What is the primary function of a combustion-air opening?
A. Cool the thermostat
B. Provide adequate air for combustion
,C. Increase duct pressure
D. Reduce return-air temperature
Answer: Provide adequate air for combustion
Rationale: Heating appliances require sufficient combustion air for proper and
safe burning of fuel.
6. What is carbon monoxide?
A. A refrigerant
B. A harmless combustion gas
C. A poisonous, odorless gas produced by incomplete combustion
D. A type of natural gas odorant
Answer: A poisonous, odorless gas produced by incomplete combustion
Rationale: Carbon monoxide is highly toxic and can result when fuel does not
burn completely.
7. What is the purpose of a flame sensor on a modern gas furnace?
A. Measure duct temperature
B. Verify that a burner flame is present
C. Measure gas pressure
D. Control blower speed
Answer: Verify that a burner flame is present
Rationale: The flame sensor confirms flame establishment and allows the
control system to shut off gas if flame is not detected.
8. What component normally opens and closes to control gas flow to a
furnace burner?
A. Blower wheel
B. Gas valve
, C. Heat exchanger
D. Draft hood
Answer: Gas valve
Rationale: The gas valve regulates the supply of fuel to the burner assembly.
9. What is the purpose of a furnace blower?
A. Supply combustion gas
B. Move heated air through the duct system
C. Increase gas pressure
D. Ignite the pilot
Answer: Move heated air through the duct system
Rationale: The blower circulates air through the furnace and into the occupied
spaces.
10.What is the purpose of a return-air duct?
A. Exhaust combustion products
B. Supply gas to the furnace
C. Return conditioned air from the building to the heating equipment
D. Supply outside combustion air
Answer: Return conditioned air from the building to the heating equipment
Rationale: Return ducts carry room air back to the furnace for reheating and
recirculation.
11.What is the purpose of supply-air ducts?
A. Remove flue gases
B. Deliver heated air to occupied spaces
C. Supply gas to burners
D. Drain condensate
Answer: Deliver heated air to occupied spaces
Examination Practice Exam 2026 | 100+
Questions & Answers with Detailed
Rationales | Complete Delaware
Heating Contractor Licensing Exam
Prep, Study Guide, Test Review &
Qualification Preparation
1. What is the primary purpose of a furnace heat exchanger?
A. Increase blower speed
B. Transfer heat from combustion gases to circulating air without mixing the two
C. Increase gas pressure
D. Reduce thermostat voltage
Answer: Transfer heat from combustion gases to circulating air without mixing
the two
Rationale: The heat exchanger transfers combustion heat to the air stream
while keeping combustion products separated from conditioned air.
2. Which component normally controls the temperature setting in a
conventional heating system?
,A. Limit switch
B. Flame sensor
C. Thermostat
D. Gas valve
Answer: Thermostat
Rationale: The thermostat senses space temperature and calls for heat when the
temperature falls below its set point.
3. What is the purpose of a furnace limit control?
A. Increase fuel pressure
B. Prevent excessive furnace temperature
C. Increase blower voltage
D. Control outdoor humidity
Answer: Prevent excessive furnace temperature
Rationale: A high-limit control shuts down or interrupts burner operation when
furnace temperature becomes unsafe.
4. Which fuel is commonly used in residential heating systems?
A. Oxygen
B. Nitrogen
C. Natural gas
D. Carbon dioxide
Answer: Natural gas
Rationale: Natural gas is a common residential heating fuel and is widely used
in furnaces, boilers, and other heating appliances.
5. What is the primary function of a combustion-air opening?
A. Cool the thermostat
B. Provide adequate air for combustion
,C. Increase duct pressure
D. Reduce return-air temperature
Answer: Provide adequate air for combustion
Rationale: Heating appliances require sufficient combustion air for proper and
safe burning of fuel.
6. What is carbon monoxide?
A. A refrigerant
B. A harmless combustion gas
C. A poisonous, odorless gas produced by incomplete combustion
D. A type of natural gas odorant
Answer: A poisonous, odorless gas produced by incomplete combustion
Rationale: Carbon monoxide is highly toxic and can result when fuel does not
burn completely.
7. What is the purpose of a flame sensor on a modern gas furnace?
A. Measure duct temperature
B. Verify that a burner flame is present
C. Measure gas pressure
D. Control blower speed
Answer: Verify that a burner flame is present
Rationale: The flame sensor confirms flame establishment and allows the
control system to shut off gas if flame is not detected.
8. What component normally opens and closes to control gas flow to a
furnace burner?
A. Blower wheel
B. Gas valve
, C. Heat exchanger
D. Draft hood
Answer: Gas valve
Rationale: The gas valve regulates the supply of fuel to the burner assembly.
9. What is the purpose of a furnace blower?
A. Supply combustion gas
B. Move heated air through the duct system
C. Increase gas pressure
D. Ignite the pilot
Answer: Move heated air through the duct system
Rationale: The blower circulates air through the furnace and into the occupied
spaces.
10.What is the purpose of a return-air duct?
A. Exhaust combustion products
B. Supply gas to the furnace
C. Return conditioned air from the building to the heating equipment
D. Supply outside combustion air
Answer: Return conditioned air from the building to the heating equipment
Rationale: Return ducts carry room air back to the furnace for reheating and
recirculation.
11.What is the purpose of supply-air ducts?
A. Remove flue gases
B. Deliver heated air to occupied spaces
C. Supply gas to burners
D. Drain condensate
Answer: Deliver heated air to occupied spaces
