STAR HVAC Mastery Exam Questions
And Correct Answers (Verified Answers)
Plus Rationales 2026 Q&A | Instant
Download Pdf
1. What is the primary function of a thermal expansion valve in an
HVAC system?
A. To increase refrigerant pressure
B. To regulate refrigerant flow into the evaporator
C. To compress refrigerant vapor
D. To circulate air through the ducts
It controls refrigerant flow to maintain proper superheat in the
evaporator.
2. Which refrigerant is commonly used as a replacement for R-22 in
residential systems?
A. R-12
B. R-410A
C. R-134a
D. R-744
R-410A is the eco-friendly replacement for R-22 due to its zero-
ozone-depletion properties.
3. What is the typical voltage for most residential split-system air
conditioners in the U.S.?
A. 115 V
, B. 230 V
C. 460 V
D. 24 V
Most residential condensers are powered by a 230-volt single-
phase circuit.
4. What does SEER stand for?
A. Seasonal Energy Exchange Ratio
B. Seasonal Energy Efficiency Ratio
C. Standard Energy Evaluation Rating
D. Seasonal Evaporator Efficiency Reading
SEER measures cooling efficiency over a full cooling season.
5. What component separates high and low pressure sides in a
refrigeration cycle?
A. Evaporator coil
B. Compressor
C. Condenser coil
D. Filter drier
The compressor compresses vapor, creating the high-pressure side.
6. What type of refrigerant oil is used with R-410A systems?
A. Mineral oil
B. POE (Polyolester) oil
C. Alkylbenzene oil
D. PAG oil
R-410A requires POE oil for proper lubrication and miscibility.
7. What is the purpose of a suction accumulator?
A. To store liquid refrigerant
B. To control superheat
, C. To prevent liquid refrigerant from entering the compressor
D. To dehumidify the air
It protects the compressor from liquid slugging.
8. In a forced-air furnace, the heat exchanger’s function is to —
A. Mix air with gas
B. Transfer heat from combustion gases to the air
C. Control airflow velocity
D. Filter airborne contaminants
It keeps combustion gases separate from indoor air while
transferring heat.
9. What does the color green typically indicate on refrigerant
cylinder labeling?
A. R-12
B. R-22
C. R-134a
D. R-404A
Green identifies R-22 cylinders under AHRI color standards.
10. Which tool measures the airflow rate in cubic feet per
minute (CFM)?
A. Anemometer
B. Manifold gauge
C. Thermocouple
D. Sling psychrometer
Anemometers calculate CFM to assess duct performance.
11. When brazing copper tubing, nitrogen is introduced into the
line to —
A. Increase temperature
And Correct Answers (Verified Answers)
Plus Rationales 2026 Q&A | Instant
Download Pdf
1. What is the primary function of a thermal expansion valve in an
HVAC system?
A. To increase refrigerant pressure
B. To regulate refrigerant flow into the evaporator
C. To compress refrigerant vapor
D. To circulate air through the ducts
It controls refrigerant flow to maintain proper superheat in the
evaporator.
2. Which refrigerant is commonly used as a replacement for R-22 in
residential systems?
A. R-12
B. R-410A
C. R-134a
D. R-744
R-410A is the eco-friendly replacement for R-22 due to its zero-
ozone-depletion properties.
3. What is the typical voltage for most residential split-system air
conditioners in the U.S.?
A. 115 V
, B. 230 V
C. 460 V
D. 24 V
Most residential condensers are powered by a 230-volt single-
phase circuit.
4. What does SEER stand for?
A. Seasonal Energy Exchange Ratio
B. Seasonal Energy Efficiency Ratio
C. Standard Energy Evaluation Rating
D. Seasonal Evaporator Efficiency Reading
SEER measures cooling efficiency over a full cooling season.
5. What component separates high and low pressure sides in a
refrigeration cycle?
A. Evaporator coil
B. Compressor
C. Condenser coil
D. Filter drier
The compressor compresses vapor, creating the high-pressure side.
6. What type of refrigerant oil is used with R-410A systems?
A. Mineral oil
B. POE (Polyolester) oil
C. Alkylbenzene oil
D. PAG oil
R-410A requires POE oil for proper lubrication and miscibility.
7. What is the purpose of a suction accumulator?
A. To store liquid refrigerant
B. To control superheat
, C. To prevent liquid refrigerant from entering the compressor
D. To dehumidify the air
It protects the compressor from liquid slugging.
8. In a forced-air furnace, the heat exchanger’s function is to —
A. Mix air with gas
B. Transfer heat from combustion gases to the air
C. Control airflow velocity
D. Filter airborne contaminants
It keeps combustion gases separate from indoor air while
transferring heat.
9. What does the color green typically indicate on refrigerant
cylinder labeling?
A. R-12
B. R-22
C. R-134a
D. R-404A
Green identifies R-22 cylinders under AHRI color standards.
10. Which tool measures the airflow rate in cubic feet per
minute (CFM)?
A. Anemometer
B. Manifold gauge
C. Thermocouple
D. Sling psychrometer
Anemometers calculate CFM to assess duct performance.
11. When brazing copper tubing, nitrogen is introduced into the
line to —
A. Increase temperature
