Missouri Hvac Contractor Exam Practice
Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. What is the primary purpose of a thermostatic expansion valve (TXV)?
A. Increase compressor pressure
B. Control refrigerant flow into evaporator
C. Remove moisture from system
D. Store refrigerant
Answer: B. Control refrigerant flow into evaporator
Rationale: The TXV regulates refrigerant entering the evaporator based on
cooling demand and superheat.
2. Which refrigerant property allows it to absorb heat at low
temperatures?
A. High density
B. Low boiling point
, C. High viscosity
D. High toxicity
Answer: B. Low boiling point
Rationale: Refrigerants absorb heat efficiently because they evaporate at
low temperatures.
3. What is the function of a capacitor in an HVAC motor circuit?
A. Store refrigerant
B. Increase airflow
C. Provide phase shift for motor starting
D. Reduce voltage permanently
Answer: C. Provide phase shift for motor starting
Rationale: Capacitors help create starting torque by shifting electrical
phase in single-phase motors.
4. Which tool is used to measure superheat?
A. Ammeter
B. Psychrometer
C. Manifold gauge set
D. Thermometer only
Answer: C. Manifold gauge set
Rationale: Superheat is determined using suction pressure and
temperature measurements.
, 5. What is the ideal airflow over an evaporator coil measured in CFM per
ton?
A. 200 CFM
B. 300 CFM
C. 400 CFM
D. 600 CFM
Answer: C. 400 CFM
Rationale: Standard HVAC design uses approximately 400 CFM per ton of
cooling.
6. What does EPA Section 608 regulate?
A. Electrical wiring
B. Refrigerant handling
C. Duct design
D. Gas piping
Answer: B. Refrigerant handling
Rationale: EPA 608 governs the use, recovery, and disposal of refrigerants.
7. What is the purpose of a heat exchanger in a furnace?
A. Store air
B. Separate combustion gases from indoor air
C. Increase humidity
D. Cool refrigerant
, Answer: B. Separate combustion gases from indoor air
Rationale: It safely transfers heat while keeping combustion gases
isolated.
8. Which refrigerant is considered an HFC?
A. R-22
B. R-410A
C. R-12
D. Ammonia
Answer: B. R-410A
Rationale: R-410A is a hydrofluorocarbon with no ozone depletion
potential.
9. What is the function of a blower motor?
A. Compress refrigerant
B. Circulate air through system
C. Heat refrigerant
D. Measure pressure
Answer: B. Circulate air through system
Rationale: The blower moves conditioned air through ducts and spaces.
10. What does subcooling indicate?
A. Refrigerant overheating
B. Liquid refrigerant below saturation temperature
Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. What is the primary purpose of a thermostatic expansion valve (TXV)?
A. Increase compressor pressure
B. Control refrigerant flow into evaporator
C. Remove moisture from system
D. Store refrigerant
Answer: B. Control refrigerant flow into evaporator
Rationale: The TXV regulates refrigerant entering the evaporator based on
cooling demand and superheat.
2. Which refrigerant property allows it to absorb heat at low
temperatures?
A. High density
B. Low boiling point
, C. High viscosity
D. High toxicity
Answer: B. Low boiling point
Rationale: Refrigerants absorb heat efficiently because they evaporate at
low temperatures.
3. What is the function of a capacitor in an HVAC motor circuit?
A. Store refrigerant
B. Increase airflow
C. Provide phase shift for motor starting
D. Reduce voltage permanently
Answer: C. Provide phase shift for motor starting
Rationale: Capacitors help create starting torque by shifting electrical
phase in single-phase motors.
4. Which tool is used to measure superheat?
A. Ammeter
B. Psychrometer
C. Manifold gauge set
D. Thermometer only
Answer: C. Manifold gauge set
Rationale: Superheat is determined using suction pressure and
temperature measurements.
, 5. What is the ideal airflow over an evaporator coil measured in CFM per
ton?
A. 200 CFM
B. 300 CFM
C. 400 CFM
D. 600 CFM
Answer: C. 400 CFM
Rationale: Standard HVAC design uses approximately 400 CFM per ton of
cooling.
6. What does EPA Section 608 regulate?
A. Electrical wiring
B. Refrigerant handling
C. Duct design
D. Gas piping
Answer: B. Refrigerant handling
Rationale: EPA 608 governs the use, recovery, and disposal of refrigerants.
7. What is the purpose of a heat exchanger in a furnace?
A. Store air
B. Separate combustion gases from indoor air
C. Increase humidity
D. Cool refrigerant
, Answer: B. Separate combustion gases from indoor air
Rationale: It safely transfers heat while keeping combustion gases
isolated.
8. Which refrigerant is considered an HFC?
A. R-22
B. R-410A
C. R-12
D. Ammonia
Answer: B. R-410A
Rationale: R-410A is a hydrofluorocarbon with no ozone depletion
potential.
9. What is the function of a blower motor?
A. Compress refrigerant
B. Circulate air through system
C. Heat refrigerant
D. Measure pressure
Answer: B. Circulate air through system
Rationale: The blower moves conditioned air through ducts and spaces.
10. What does subcooling indicate?
A. Refrigerant overheating
B. Liquid refrigerant below saturation temperature
