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. In North Carolina, which function most directly distinguishes a heating
contractor's scope of work from that of a general building contractor
when performing regulated HVAC work?
A. Installing interior trim around mechanical equipment
B. Installing, servicing, maintaining, or repairing heating and air-
conditioning systems within the contractor's authorized classification
C. Installing all electrical service equipment associated with a building
D. Performing structural foundation repairs beneath mechanical equipment
Rationale: The HVAC classification is intended to regulate specialized
heating and air-conditioning work, including installation, service,
,maintenance, and repair of mechanical systems within the contractor's
authorized scope.
2. A forced-air heating system is rated at 80,000 Btu/h input and has an
efficiency of 80 percent. Approximately how much useful heat is
delivered to the conditioned space at full rated operation, assuming
the stated efficiency represents the useful output-to-input ratio?
A. 16,000 Btu/h
B. 32,000 Btu/h
C. 64,000 Btu/h
D. 100,000 Btu/h
Rationale: Useful output is calculated by multiplying input capacity by
efficiency: 80,000 × 0.80 = 64,000 Btu/h.
3. Which measurement is most useful for determining whether an
operating gas furnace is delivering an appropriate temperature rise
across its heat exchanger and supply-air section?
A. Outdoor relative humidity
B. Refrigerant subcooling
C. Temperature difference between return air and supply air
D. Static pressure of the gas utility main
,Rationale: Furnace temperature rise is determined from the difference
between return-air temperature and supply-air temperature and is
compared with the manufacturer's specified range.
4. A furnace manufacturer specifies a temperature rise of 35°F to 65°F.
During commissioning, the measured temperature rise is 78°F. Which
condition is most likely responsible?
A. Excessive airflow through the furnace
B. Insufficient airflow through the furnace
C. Excessive outdoor humidity
D. Oversized return-air grille with unrestricted airflow
Rationale: Excessive temperature rise commonly results from inadequate
airflow, because insufficient air removes less heat from the furnace heat
exchanger and raises supply-air temperature.
5. What is the primary purpose of a furnace's high-limit control?
A. To regulate the gas supply pressure continuously
B. To maintain constant room humidity
C. To shut down or control burner operation when furnace temperature
becomes excessive
D. To increase blower speed whenever the thermostat is satisfied
, Rationale: The high-limit control is a safety device that protects the
furnace from excessive temperatures caused by conditions such as
inadequate airflow or abnormal operation.
6. Which condition can cause a forced-air furnace to overheat even
though the burners are operating at their rated input?
A. An oversized return-air filter with low resistance
B. A severely restricted air filter or blocked supply-air system
C. A clean heat exchanger with correct airflow
D. A properly adjusted blower operating at design airflow
Rationale: Restrictions in the air-distribution system reduce airflow across
the heat exchanger, causing excessive temperature rise and potentially
activating the high-limit control.
7. When sizing a replacement heating system for a building, which factor
should receive primary consideration rather than simply matching the
input capacity of the old equipment?
A. The color of the existing furnace
B. The age of the thermostat alone
C. The calculated heating load of the building and the equipment
manufacturer's sizing requirements
D. The electrical rating of the existing lighting system
Contractors Board – Heating (HVAC)
Contractor Exam Practice Questions
And Correct Answers (Verified Answers)
Plus Rationale 2027 Q&A| Instant
Download Pdf.
1. In North Carolina, which function most directly distinguishes a heating
contractor's scope of work from that of a general building contractor
when performing regulated HVAC work?
A. Installing interior trim around mechanical equipment
B. Installing, servicing, maintaining, or repairing heating and air-
conditioning systems within the contractor's authorized classification
C. Installing all electrical service equipment associated with a building
D. Performing structural foundation repairs beneath mechanical equipment
Rationale: The HVAC classification is intended to regulate specialized
heating and air-conditioning work, including installation, service,
,maintenance, and repair of mechanical systems within the contractor's
authorized scope.
2. A forced-air heating system is rated at 80,000 Btu/h input and has an
efficiency of 80 percent. Approximately how much useful heat is
delivered to the conditioned space at full rated operation, assuming
the stated efficiency represents the useful output-to-input ratio?
A. 16,000 Btu/h
B. 32,000 Btu/h
C. 64,000 Btu/h
D. 100,000 Btu/h
Rationale: Useful output is calculated by multiplying input capacity by
efficiency: 80,000 × 0.80 = 64,000 Btu/h.
3. Which measurement is most useful for determining whether an
operating gas furnace is delivering an appropriate temperature rise
across its heat exchanger and supply-air section?
A. Outdoor relative humidity
B. Refrigerant subcooling
C. Temperature difference between return air and supply air
D. Static pressure of the gas utility main
,Rationale: Furnace temperature rise is determined from the difference
between return-air temperature and supply-air temperature and is
compared with the manufacturer's specified range.
4. A furnace manufacturer specifies a temperature rise of 35°F to 65°F.
During commissioning, the measured temperature rise is 78°F. Which
condition is most likely responsible?
A. Excessive airflow through the furnace
B. Insufficient airflow through the furnace
C. Excessive outdoor humidity
D. Oversized return-air grille with unrestricted airflow
Rationale: Excessive temperature rise commonly results from inadequate
airflow, because insufficient air removes less heat from the furnace heat
exchanger and raises supply-air temperature.
5. What is the primary purpose of a furnace's high-limit control?
A. To regulate the gas supply pressure continuously
B. To maintain constant room humidity
C. To shut down or control burner operation when furnace temperature
becomes excessive
D. To increase blower speed whenever the thermostat is satisfied
, Rationale: The high-limit control is a safety device that protects the
furnace from excessive temperatures caused by conditions such as
inadequate airflow or abnormal operation.
6. Which condition can cause a forced-air furnace to overheat even
though the burners are operating at their rated input?
A. An oversized return-air filter with low resistance
B. A severely restricted air filter or blocked supply-air system
C. A clean heat exchanger with correct airflow
D. A properly adjusted blower operating at design airflow
Rationale: Restrictions in the air-distribution system reduce airflow across
the heat exchanger, causing excessive temperature rise and potentially
activating the high-limit control.
7. When sizing a replacement heating system for a building, which factor
should receive primary consideration rather than simply matching the
input capacity of the old equipment?
A. The color of the existing furnace
B. The age of the thermostat alone
C. The calculated heating load of the building and the equipment
manufacturer's sizing requirements
D. The electrical rating of the existing lighting system
