DC Heating Systems Installer Exam
Practice Questions And Correct Answers
(Verified Answers) Plus Rationale 2026
Q&A| Instant Download Pdf
1. Which component in a forced-air heating system is primarily
responsible for transferring heat from combustion gases to the air
supplied to occupied spaces?
A. Expansion valve
B. Condenser coil
C. Heat exchanger
D. Evaporator coil
Rationale: The heat exchanger transfers thermal energy from combustion
gases to the circulating air while preventing combustion products,
including carbon monoxide, from entering the occupied space.
2. Before installing a gas-fired heating appliance, an installer should first
verify that:
A. The thermostat is programmable.
B. The ductwork is painted.
C. The appliance input rating matches the building heating load.
D. The blower motor is oversized.
,Rationale: Proper equipment sizing ensures efficiency, comfort, and code
compliance while preventing short cycling and excessive energy
consumption.
3. A furnace limit switch is designed primarily to:
A. Increase blower speed.
B. Control gas pressure.
C. Prevent overheating by interrupting burner operation.
D. Measure room humidity.
Rationale: The limit switch protects the furnace from excessive
temperatures by shutting off the burner if unsafe operating conditions
occur.
4. Which fuel requires proper venting because combustion produces
carbon monoxide?
A. Solar energy
B. Electricity
C. Natural gas
D. Hydronic water
Rationale: Natural gas combustion produces combustion gases that must
be safely vented outdoors to protect occupants from carbon monoxide
exposure.
5. In a hydronic heating system, the circulator pump is responsible for:
A. Compressing refrigerant.
B. Heating domestic water.
C. Moving heated water through the piping system.
D. Controlling combustion air.
Rationale: The circulator pump provides continuous water flow between
the boiler and heat emitters for effective heat distribution.
, 6. Which instrument is commonly used to verify gas manifold pressure?
A. Clamp ammeter
B. Infrared thermometer
C. Manometer
D. Megohmmeter
Rationale: A manometer accurately measures gas pressure to ensure
proper burner performance according to manufacturer specifications.
7. Proper combustion air is necessary because it:
A. Reduces blower speed.
B. Eliminates duct insulation.
C. Supports complete combustion and safe appliance operation.
D. Prevents thermostat failure.
Rationale: Adequate combustion air ensures efficient fuel burning while
minimizing carbon monoxide production.
8. Which thermostat terminal typically energizes the heating circuit?
A. G
B. Y
C. W
D. O
Rationale: The W terminal is commonly used to call for heating in
residential HVAC control systems.
9. During furnace installation, the vent connector should generally:
A. Slope downward toward the furnace.
B. Be installed horizontally without support.
C. Slope upward toward the chimney or vent termination.
D. Be submerged below grade.
Rationale: An upward slope encourages proper draft and safe removal of
combustion products.
Practice Questions And Correct Answers
(Verified Answers) Plus Rationale 2026
Q&A| Instant Download Pdf
1. Which component in a forced-air heating system is primarily
responsible for transferring heat from combustion gases to the air
supplied to occupied spaces?
A. Expansion valve
B. Condenser coil
C. Heat exchanger
D. Evaporator coil
Rationale: The heat exchanger transfers thermal energy from combustion
gases to the circulating air while preventing combustion products,
including carbon monoxide, from entering the occupied space.
2. Before installing a gas-fired heating appliance, an installer should first
verify that:
A. The thermostat is programmable.
B. The ductwork is painted.
C. The appliance input rating matches the building heating load.
D. The blower motor is oversized.
,Rationale: Proper equipment sizing ensures efficiency, comfort, and code
compliance while preventing short cycling and excessive energy
consumption.
3. A furnace limit switch is designed primarily to:
A. Increase blower speed.
B. Control gas pressure.
C. Prevent overheating by interrupting burner operation.
D. Measure room humidity.
Rationale: The limit switch protects the furnace from excessive
temperatures by shutting off the burner if unsafe operating conditions
occur.
4. Which fuel requires proper venting because combustion produces
carbon monoxide?
A. Solar energy
B. Electricity
C. Natural gas
D. Hydronic water
Rationale: Natural gas combustion produces combustion gases that must
be safely vented outdoors to protect occupants from carbon monoxide
exposure.
5. In a hydronic heating system, the circulator pump is responsible for:
A. Compressing refrigerant.
B. Heating domestic water.
C. Moving heated water through the piping system.
D. Controlling combustion air.
Rationale: The circulator pump provides continuous water flow between
the boiler and heat emitters for effective heat distribution.
, 6. Which instrument is commonly used to verify gas manifold pressure?
A. Clamp ammeter
B. Infrared thermometer
C. Manometer
D. Megohmmeter
Rationale: A manometer accurately measures gas pressure to ensure
proper burner performance according to manufacturer specifications.
7. Proper combustion air is necessary because it:
A. Reduces blower speed.
B. Eliminates duct insulation.
C. Supports complete combustion and safe appliance operation.
D. Prevents thermostat failure.
Rationale: Adequate combustion air ensures efficient fuel burning while
minimizing carbon monoxide production.
8. Which thermostat terminal typically energizes the heating circuit?
A. G
B. Y
C. W
D. O
Rationale: The W terminal is commonly used to call for heating in
residential HVAC control systems.
9. During furnace installation, the vent connector should generally:
A. Slope downward toward the furnace.
B. Be installed horizontally without support.
C. Slope upward toward the chimney or vent termination.
D. Be submerged below grade.
Rationale: An upward slope encourages proper draft and safe removal of
combustion products.
