NATE FINAL EXAM PREP: 200 COMPREHENSIVE QUESTIONS
(2026/2027 UPDATE) COMPLETE WITH VERIFIED ANSWERS
1. Which of the following is the correct procedure for checking the
charge of a system using the superheat method?
A. Measure the suction line pressure and temperature, then compare to
the chart.
B. Measure the liquid line pressure and temperature, then compare to
the chart.
C. Measure the discharge line pressure and temperature, then compare
to the chart.
D. Measure the ambient air temperature and subtract it from the
suction line temperature.
Answer: A
Rationale: The superheat method is specifically used for fixed orifice
metering devices. It requires measuring the suction line pressure (to
find the saturation temperature) and the suction line temperature, then
calculating the difference.
2. A technician is installing a new thermostat. The system has a heat
pump with auxiliary electric heat. Which terminal on the thermostat is
typically used to energize the reversing valve in the cooling mode?
A. W1
B. O
C. G
D. Y1
Answer: B
,Rationale: The "O" terminal is conventionally used to energize the
reversing valve in the cooling mode (though "B" is used in some brands
for heating mode). W1 is for auxiliary heat, G is for the indoor blower,
and Y1 is for the compressor contactor.
3. When brazing copper tubing, what is the primary purpose of
flowing nitrogen through the system?
A. To cool the tubing to prevent melting.
B. To prevent oxidation and scale formation inside the tubing.
C. To increase the pressure for a better joint.
D. To act as a flux for the filler material.
Answer: B
Rationale: Flowing nitrogen displaces oxygen inside the tubing during
the brazing process. This prevents the formation of copper oxide (scale)
which can clog filters, metering devices, and damage the compressor.
4. A compressor is short-cycling. Which of the following is the most
likely cause?
A. A dirty air filter.
B. A low refrigerant charge.
C. A faulty high-pressure cutout switch.
D. A defective run capacitor.
Answer: C
Rationale: Short cycling (frequent starting and stopping) is often caused
by safety switches tripping prematurely. A faulty high-pressure switch
can open the circuit before the system reaches full capacity, causing the
compressor to stop, then restart when pressure drops.
5. What is the primary function of a crankcase heater on a
compressor?
,A. To warm the compressor oil to prevent refrigerant migration.
B. To increase the compressor's heating capacity.
C. To reduce the noise level during startup.
D. To cool the compressor during hot weather.
Answer: A
Rationale: The crankcase heater keeps the oil in the compressor sump
warmer than the coldest part of the system. This prevents refrigerant
from condensing and mixing with the oil (migration), which would cause
oil dilution and potential compressor failure.
6. In a ducted system, what is the recommended maximum static
pressure for a typical residential blower motor?
A. 0.1 inches of water column
B. 0.5 inches of water column
C. 1.0 inches of water column
D. 2.0 inches of water column
Answer: B
Rationale: Most residential blowers are designed to operate within a
total external static pressure range of 0.2 to 0.8 inches of water column.
0.5 is a common standard rating point for performance.
7. Which of the following refrigerants is classified as an A2L (mildly
flammable) refrigerant?
A. R-410A
B. R-22
C. R-32
D. R-134a
Answer: C
Rationale: R-32 is a widely used A2L refrigerant. R-410A and R-22 are
, A1 (non-flammable), and R-134a is also A1. A2L refrigerants are
becoming more common due to environmental regulations.
8. A technician measures a temperature rise across the evaporator coil
of 25°F. The system uses R-410A. What does this indicate?
A. The system is overcharged.
B. The system is undercharged or has low airflow.
C. The system is operating perfectly.
D. The compressor is failing.
Answer: B
Rationale: A high temperature rise (delta T) across the evaporator
usually indicates low airflow (dirty filter, closed registers) or a low
refrigerant charge. The standard range is typically 16-22°F.
9. What is the correct tool to use for measuring the diameter of a
copper pipe?
A. A micrometer.
B. A tape measure.
C. A tubing cutter.
D. A pipe wrench.
Answer: A
Rationale: A micrometer or a vernier caliper is used for precise
measurement of pipe diameter. A tape measure is not accurate enough
for ACR (Air Conditioning and Refrigeration) tubing sizes.
10. When replacing a compressor, what should be installed on the
suction line to protect the new compressor from debris?
A. A liquid line filter drier.
B. A suction line filter drier.
C. A muffler.
(2026/2027 UPDATE) COMPLETE WITH VERIFIED ANSWERS
1. Which of the following is the correct procedure for checking the
charge of a system using the superheat method?
A. Measure the suction line pressure and temperature, then compare to
the chart.
B. Measure the liquid line pressure and temperature, then compare to
the chart.
C. Measure the discharge line pressure and temperature, then compare
to the chart.
D. Measure the ambient air temperature and subtract it from the
suction line temperature.
Answer: A
Rationale: The superheat method is specifically used for fixed orifice
metering devices. It requires measuring the suction line pressure (to
find the saturation temperature) and the suction line temperature, then
calculating the difference.
2. A technician is installing a new thermostat. The system has a heat
pump with auxiliary electric heat. Which terminal on the thermostat is
typically used to energize the reversing valve in the cooling mode?
A. W1
B. O
C. G
D. Y1
Answer: B
,Rationale: The "O" terminal is conventionally used to energize the
reversing valve in the cooling mode (though "B" is used in some brands
for heating mode). W1 is for auxiliary heat, G is for the indoor blower,
and Y1 is for the compressor contactor.
3. When brazing copper tubing, what is the primary purpose of
flowing nitrogen through the system?
A. To cool the tubing to prevent melting.
B. To prevent oxidation and scale formation inside the tubing.
C. To increase the pressure for a better joint.
D. To act as a flux for the filler material.
Answer: B
Rationale: Flowing nitrogen displaces oxygen inside the tubing during
the brazing process. This prevents the formation of copper oxide (scale)
which can clog filters, metering devices, and damage the compressor.
4. A compressor is short-cycling. Which of the following is the most
likely cause?
A. A dirty air filter.
B. A low refrigerant charge.
C. A faulty high-pressure cutout switch.
D. A defective run capacitor.
Answer: C
Rationale: Short cycling (frequent starting and stopping) is often caused
by safety switches tripping prematurely. A faulty high-pressure switch
can open the circuit before the system reaches full capacity, causing the
compressor to stop, then restart when pressure drops.
5. What is the primary function of a crankcase heater on a
compressor?
,A. To warm the compressor oil to prevent refrigerant migration.
B. To increase the compressor's heating capacity.
C. To reduce the noise level during startup.
D. To cool the compressor during hot weather.
Answer: A
Rationale: The crankcase heater keeps the oil in the compressor sump
warmer than the coldest part of the system. This prevents refrigerant
from condensing and mixing with the oil (migration), which would cause
oil dilution and potential compressor failure.
6. In a ducted system, what is the recommended maximum static
pressure for a typical residential blower motor?
A. 0.1 inches of water column
B. 0.5 inches of water column
C. 1.0 inches of water column
D. 2.0 inches of water column
Answer: B
Rationale: Most residential blowers are designed to operate within a
total external static pressure range of 0.2 to 0.8 inches of water column.
0.5 is a common standard rating point for performance.
7. Which of the following refrigerants is classified as an A2L (mildly
flammable) refrigerant?
A. R-410A
B. R-22
C. R-32
D. R-134a
Answer: C
Rationale: R-32 is a widely used A2L refrigerant. R-410A and R-22 are
, A1 (non-flammable), and R-134a is also A1. A2L refrigerants are
becoming more common due to environmental regulations.
8. A technician measures a temperature rise across the evaporator coil
of 25°F. The system uses R-410A. What does this indicate?
A. The system is overcharged.
B. The system is undercharged or has low airflow.
C. The system is operating perfectly.
D. The compressor is failing.
Answer: B
Rationale: A high temperature rise (delta T) across the evaporator
usually indicates low airflow (dirty filter, closed registers) or a low
refrigerant charge. The standard range is typically 16-22°F.
9. What is the correct tool to use for measuring the diameter of a
copper pipe?
A. A micrometer.
B. A tape measure.
C. A tubing cutter.
D. A pipe wrench.
Answer: A
Rationale: A micrometer or a vernier caliper is used for precise
measurement of pipe diameter. A tape measure is not accurate enough
for ACR (Air Conditioning and Refrigeration) tubing sizes.
10. When replacing a compressor, what should be installed on the
suction line to protect the new compressor from debris?
A. A liquid line filter drier.
B. A suction line filter drier.
C. A muffler.
