Missouri HVAC Service Technician Exam
Practice Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. What is the primary function of a thermostat in an HVAC system?
A. Increase refrigerant pressure
B. Measure air humidity
C. Control temperature by regulating system operation
D. Filter airborne particles
Correct Answer: C
The thermostat senses indoor temperature and signals the HVAC
system to start or stop heating or cooling to maintain the desired
setpoint.
2. Which refrigerant is commonly used in newer residential HVAC
systems?
A. R-22
B. R-410A
C. R-12
, D. Ammonia
Correct Answer: B
R-410A is widely used in modern systems due to its higher efficiency
and lower ozone depletion potential compared to older refrigerants.
3. What does superheat measure in a refrigeration system?
A. Liquid line temperature
B. Temperature of refrigerant above its boiling point in the evaporator
C. Condenser coil temperature difference
D. Compressor oil temperature
Correct Answer: B
Superheat indicates how much the refrigerant vapor has been heated
beyond its saturation temperature after evaporation.
4. What is the purpose of a capacitor in an HVAC motor circuit?
A. Store refrigerant
B. Increase airflow
C. Provide starting torque to motors
D. Reduce voltage permanently
Correct Answer: C
A capacitor stores and releases electrical energy to help start or run
motors efficiently.
5. Which component removes moisture and contaminants from
refrigerant?
A. Compressor
, B. Expansion valve
C. Filter drier
D. Evaporator
Correct Answer: C
A filter drier absorbs moisture and filters debris to protect system
components.
6. What is the main function of a compressor?
A. Expand refrigerant
B. Circulate and pressurize refrigerant
C. Cool indoor air directly
D. Remove humidity
Correct Answer: B
The compressor raises refrigerant pressure and circulates it through
the system.
7. What type of heat transfer occurs in a furnace heat exchanger?
A. Radiation only
B. Conduction only
C. Convection only
D. Combination of conduction and convection
Correct Answer: D
Heat is conducted through the exchanger walls and then transferred
to air via convection.
, 8. What is the function of an expansion valve?
A. Compress refrigerant
B. Increase refrigerant temperature
C. Regulate refrigerant flow into evaporator
D. Store refrigerant
Correct Answer: C
The expansion valve controls refrigerant flow and reduces pressure
before it enters the evaporator.
9. What does BTU measure in HVAC systems?
A. Electrical resistance
B. Heat energy
C. Air velocity
D. Pressure differential
Correct Answer: B
BTU (British Thermal Unit) measures the amount of heat energy
required to raise one pound of water by one degree Fahrenheit.
10. What is the purpose of a condenser coil?
A. Absorb indoor heat
B. Reject heat to outdoor air
C. Filter air
D. Compress refrigerant
Correct Answer: B
Practice Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. What is the primary function of a thermostat in an HVAC system?
A. Increase refrigerant pressure
B. Measure air humidity
C. Control temperature by regulating system operation
D. Filter airborne particles
Correct Answer: C
The thermostat senses indoor temperature and signals the HVAC
system to start or stop heating or cooling to maintain the desired
setpoint.
2. Which refrigerant is commonly used in newer residential HVAC
systems?
A. R-22
B. R-410A
C. R-12
, D. Ammonia
Correct Answer: B
R-410A is widely used in modern systems due to its higher efficiency
and lower ozone depletion potential compared to older refrigerants.
3. What does superheat measure in a refrigeration system?
A. Liquid line temperature
B. Temperature of refrigerant above its boiling point in the evaporator
C. Condenser coil temperature difference
D. Compressor oil temperature
Correct Answer: B
Superheat indicates how much the refrigerant vapor has been heated
beyond its saturation temperature after evaporation.
4. What is the purpose of a capacitor in an HVAC motor circuit?
A. Store refrigerant
B. Increase airflow
C. Provide starting torque to motors
D. Reduce voltage permanently
Correct Answer: C
A capacitor stores and releases electrical energy to help start or run
motors efficiently.
5. Which component removes moisture and contaminants from
refrigerant?
A. Compressor
, B. Expansion valve
C. Filter drier
D. Evaporator
Correct Answer: C
A filter drier absorbs moisture and filters debris to protect system
components.
6. What is the main function of a compressor?
A. Expand refrigerant
B. Circulate and pressurize refrigerant
C. Cool indoor air directly
D. Remove humidity
Correct Answer: B
The compressor raises refrigerant pressure and circulates it through
the system.
7. What type of heat transfer occurs in a furnace heat exchanger?
A. Radiation only
B. Conduction only
C. Convection only
D. Combination of conduction and convection
Correct Answer: D
Heat is conducted through the exchanger walls and then transferred
to air via convection.
, 8. What is the function of an expansion valve?
A. Compress refrigerant
B. Increase refrigerant temperature
C. Regulate refrigerant flow into evaporator
D. Store refrigerant
Correct Answer: C
The expansion valve controls refrigerant flow and reduces pressure
before it enters the evaporator.
9. What does BTU measure in HVAC systems?
A. Electrical resistance
B. Heat energy
C. Air velocity
D. Pressure differential
Correct Answer: B
BTU (British Thermal Unit) measures the amount of heat energy
required to raise one pound of water by one degree Fahrenheit.
10. What is the purpose of a condenser coil?
A. Absorb indoor heat
B. Reject heat to outdoor air
C. Filter air
D. Compress refrigerant
Correct Answer: B
