NC Plumbing, Heating & Fire Sprinkler
Contractors Board – Heating (HVAC)
Contractor Exam Practice Questions
And Correct Answers (Verified Answers)
Plus Rationale 2027 Q&A| Instant
Download Pdf.
1. Which component of a forced-air heating system is primarily
responsible for transferring heat from the combustion process to the
circulating air without allowing combustion gases to mix with the
conditioned air?
A. Blower wheel
B. Heat exchanger
C. Expansion valve
D. Condenser coil
The heat exchanger transfers heat from combustion gases to the
circulating air while maintaining separation between the combustion
products and indoor air.
, 2. In a gas-fired furnace, what is the primary purpose of the draft inducer
motor?
A. Increase the temperature of supply air
B. Circulate conditioned air through the duct system
C. Establish proper combustion airflow and help move flue gases
through the venting system
D. Regulate the gas pressure entering the burners
The draft inducer establishes the required airflow through the combustion
and venting passages before and during burner operation, helping ensure
safe removal of combustion products.
3. A furnace repeatedly begins an ignition sequence but shuts down
shortly after the burners ignite. The flame sensor is suspected. What is
the most appropriate initial diagnostic consideration?
A. The blower motor is oversized
B. The evaporator coil is dirty
C. The control may be failing to prove the presence of flame
D. The thermostat anticipator is too large
A flame-proving device such as a flame sensor allows the control system to
verify that safe burner ignition has occurred; failure to prove flame can
cause the gas valve to close shortly after ignition.
, 4. What is the principal purpose of a high-limit control in a forced-air
furnace?
A. Prevent excessive gas pressure at the utility meter
B. Maintain constant return-air temperature
C. Control outdoor combustion air
D. Prevent the furnace from operating at an excessively high
temperature
The high-limit control protects the furnace from overheating by
interrupting burner operation when the heat exchanger or supply-air
temperature becomes excessive.
5. When measuring temperature rise across a gas furnace, which
condition generally indicates that the measured temperature rise is
significantly above the manufacturer's specified range?
A. Excessive return-air temperature only
B. Insufficient airflow across the heat exchanger
C. Excessive outdoor humidity
D. Oversized return-air grilles
Insufficient airflow reduces the amount of air available to absorb heat
from the heat exchanger, causing the supply-air temperature and
measured temperature rise to increase.
, 6. What is the primary function of a furnace blower in a forced-air
heating system?
A. Supply combustion air to the burners
B. Remove flue gases from the heat exchanger
C. Move conditioned air through the furnace and distribution system
D. Regulate manifold gas pressure
The blower moves return air across the heat exchanger and then
distributes the heated air through the supply duct system.
7. A furnace manufacturer specifies a temperature rise of 35°F to 65°F,
but a technician measures a 78°F rise. Which condition should receive
particular attention?
A. Excessive outdoor ventilation
B. Low airflow through the furnace
C. Low gas pressure at the meter caused solely by the thermostat
D. Oversized supply registers
A temperature rise above the manufacturer's specified range commonly
indicates inadequate airflow, although other operating conditions should
also be investigated before making a final diagnosis.
8. What is the primary purpose of a furnace filter in a forced-air HVAC
system?
A. Remove carbon monoxide from combustion gases
Contractors Board – Heating (HVAC)
Contractor Exam Practice Questions
And Correct Answers (Verified Answers)
Plus Rationale 2027 Q&A| Instant
Download Pdf.
1. Which component of a forced-air heating system is primarily
responsible for transferring heat from the combustion process to the
circulating air without allowing combustion gases to mix with the
conditioned air?
A. Blower wheel
B. Heat exchanger
C. Expansion valve
D. Condenser coil
The heat exchanger transfers heat from combustion gases to the
circulating air while maintaining separation between the combustion
products and indoor air.
, 2. In a gas-fired furnace, what is the primary purpose of the draft inducer
motor?
A. Increase the temperature of supply air
B. Circulate conditioned air through the duct system
C. Establish proper combustion airflow and help move flue gases
through the venting system
D. Regulate the gas pressure entering the burners
The draft inducer establishes the required airflow through the combustion
and venting passages before and during burner operation, helping ensure
safe removal of combustion products.
3. A furnace repeatedly begins an ignition sequence but shuts down
shortly after the burners ignite. The flame sensor is suspected. What is
the most appropriate initial diagnostic consideration?
A. The blower motor is oversized
B. The evaporator coil is dirty
C. The control may be failing to prove the presence of flame
D. The thermostat anticipator is too large
A flame-proving device such as a flame sensor allows the control system to
verify that safe burner ignition has occurred; failure to prove flame can
cause the gas valve to close shortly after ignition.
, 4. What is the principal purpose of a high-limit control in a forced-air
furnace?
A. Prevent excessive gas pressure at the utility meter
B. Maintain constant return-air temperature
C. Control outdoor combustion air
D. Prevent the furnace from operating at an excessively high
temperature
The high-limit control protects the furnace from overheating by
interrupting burner operation when the heat exchanger or supply-air
temperature becomes excessive.
5. When measuring temperature rise across a gas furnace, which
condition generally indicates that the measured temperature rise is
significantly above the manufacturer's specified range?
A. Excessive return-air temperature only
B. Insufficient airflow across the heat exchanger
C. Excessive outdoor humidity
D. Oversized return-air grilles
Insufficient airflow reduces the amount of air available to absorb heat
from the heat exchanger, causing the supply-air temperature and
measured temperature rise to increase.
, 6. What is the primary function of a furnace blower in a forced-air
heating system?
A. Supply combustion air to the burners
B. Remove flue gases from the heat exchanger
C. Move conditioned air through the furnace and distribution system
D. Regulate manifold gas pressure
The blower moves return air across the heat exchanger and then
distributes the heated air through the supply duct system.
7. A furnace manufacturer specifies a temperature rise of 35°F to 65°F,
but a technician measures a 78°F rise. Which condition should receive
particular attention?
A. Excessive outdoor ventilation
B. Low airflow through the furnace
C. Low gas pressure at the meter caused solely by the thermostat
D. Oversized supply registers
A temperature rise above the manufacturer's specified range commonly
indicates inadequate airflow, although other operating conditions should
also be investigated before making a final diagnosis.
8. What is the primary purpose of a furnace filter in a forced-air HVAC
system?
A. Remove carbon monoxide from combustion gases
