NATE Core Service Certification Practice
Exam Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. Which of the following is the primary purpose of a heat exchanger in a
furnace?
A. Increase electrical efficiency
B. Transfer heat from combustion gases to air
C. Filter air entering the system
D. Reduce noise
Rationale: The heat exchanger’s main function is to transfer heat
from the combustion gases to the air circulated through the home.
2. What is the most common refrigerant used in modern residential
HVAC systems?
A. R-22
B. R-11
C. R-410A
, D. R-134a
Rationale: R-410A is the current standard for new residential air
conditioning and heat pump systems due to its efficiency and
environmental compliance.
3. Which type of furnace uses a sealed combustion system?
A. Gravity furnace
B. Atmospheric furnace
C. Direct vent furnace
D. Upflow gravity furnace
Rationale: Direct vent furnaces draw combustion air from outside
and vent exhaust outside, making them sealed combustion systems.
4. What is the main purpose of a capacitor in an electric motor?
A. Reduce voltage
B. Start and/or run the motor efficiently
C. Filter electrical noise
D. Prevent overheating
Rationale: Capacitors store energy and provide the extra torque
needed to start or run single-phase motors efficiently.
5. Which of the following is a common symptom of a clogged air filter?
A. Compressor short cycling
B. Reduced airflow and system efficiency
C. Excessive refrigerant pressure
D. Flame rollout
, Rationale: A dirty filter restricts airflow, reducing efficiency and
potentially causing other system issues.
6. In a split air conditioning system, the condenser is located:
A. Inside the furnace plenum
B. Outside the home
C. In the ductwork
D. Above the evaporator coil
Rationale: The condenser is located outdoors to reject heat from the
refrigerant to the ambient air.
7. What is the purpose of a thermostat in an HVAC system?
A. Increase refrigerant flow
B. Control the operation of heating and cooling equipment
C. Remove humidity
D. Clean the air
Rationale: The thermostat senses temperature and turns HVAC
equipment on or off to maintain comfort.
8. Which of the following is a sign of a refrigerant leak?
A. High indoor humidity
B. Ice formation on the evaporator coil
C. Excessive airflow
D. Low gas pressure
Rationale: Low refrigerant can cause the evaporator coil to get too
cold, forming ice as moisture freezes.
, 9. What is the primary purpose of the blower motor in a furnace?
A. Heat air
B. Move air through the ducts
C. Vent combustion gases
D. Control humidity
Rationale: The blower motor circulates conditioned air through the
duct system.
10. Which type of combustion appliance vent relies on natural draft
to expel combustion gases?
A. Direct vent
B. B-vent
C. Power vent
D. Sealed combustion
Rationale: B-vent (Type B) relies on the buoyancy of hot gases to rise
naturally out of the vent.
11. What safety device prevents a gas furnace from operating if the
burner flame goes out?
A. Limit switch
B. Pressure switch
C. Flame sensor
D. Thermostat
Rationale: A flame sensor detects the presence of a flame and shuts
off the gas valve if the flame is absent.
Exam Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. Which of the following is the primary purpose of a heat exchanger in a
furnace?
A. Increase electrical efficiency
B. Transfer heat from combustion gases to air
C. Filter air entering the system
D. Reduce noise
Rationale: The heat exchanger’s main function is to transfer heat
from the combustion gases to the air circulated through the home.
2. What is the most common refrigerant used in modern residential
HVAC systems?
A. R-22
B. R-11
C. R-410A
, D. R-134a
Rationale: R-410A is the current standard for new residential air
conditioning and heat pump systems due to its efficiency and
environmental compliance.
3. Which type of furnace uses a sealed combustion system?
A. Gravity furnace
B. Atmospheric furnace
C. Direct vent furnace
D. Upflow gravity furnace
Rationale: Direct vent furnaces draw combustion air from outside
and vent exhaust outside, making them sealed combustion systems.
4. What is the main purpose of a capacitor in an electric motor?
A. Reduce voltage
B. Start and/or run the motor efficiently
C. Filter electrical noise
D. Prevent overheating
Rationale: Capacitors store energy and provide the extra torque
needed to start or run single-phase motors efficiently.
5. Which of the following is a common symptom of a clogged air filter?
A. Compressor short cycling
B. Reduced airflow and system efficiency
C. Excessive refrigerant pressure
D. Flame rollout
, Rationale: A dirty filter restricts airflow, reducing efficiency and
potentially causing other system issues.
6. In a split air conditioning system, the condenser is located:
A. Inside the furnace plenum
B. Outside the home
C. In the ductwork
D. Above the evaporator coil
Rationale: The condenser is located outdoors to reject heat from the
refrigerant to the ambient air.
7. What is the purpose of a thermostat in an HVAC system?
A. Increase refrigerant flow
B. Control the operation of heating and cooling equipment
C. Remove humidity
D. Clean the air
Rationale: The thermostat senses temperature and turns HVAC
equipment on or off to maintain comfort.
8. Which of the following is a sign of a refrigerant leak?
A. High indoor humidity
B. Ice formation on the evaporator coil
C. Excessive airflow
D. Low gas pressure
Rationale: Low refrigerant can cause the evaporator coil to get too
cold, forming ice as moisture freezes.
, 9. What is the primary purpose of the blower motor in a furnace?
A. Heat air
B. Move air through the ducts
C. Vent combustion gases
D. Control humidity
Rationale: The blower motor circulates conditioned air through the
duct system.
10. Which type of combustion appliance vent relies on natural draft
to expel combustion gases?
A. Direct vent
B. B-vent
C. Power vent
D. Sealed combustion
Rationale: B-vent (Type B) relies on the buoyancy of hot gases to rise
naturally out of the vent.
11. What safety device prevents a gas furnace from operating if the
burner flame goes out?
A. Limit switch
B. Pressure switch
C. Flame sensor
D. Thermostat
Rationale: A flame sensor detects the presence of a flame and shuts
off the gas valve if the flame is absent.
