NATE AC Service Certification Exam
2025 Questions and Answers
A system is supplied from the factory with charge of 5 pounds 10 ounces for a 15 foot line set. The
line set is 25 feet long. The manufacturer's instruction sheet specifies 0.6 ounces of refrigeration to
be added for each added foot of refrigerant line set length. What is the total refrigerant charge for
the system?
A. 6 ounces
B. 5 pounds
C. 5 pounds 10 ounces
D. 6 pounds - ANSWER✔✔-D. 6 pounds
15ft - 25ft = 10ft x .6 = 6 ounces
5 pounds + 10 ounces + 6 ounces
5 pounds + 16 ounces = 6 pounds
The purpose of using flux when soldering is to:
FOR STUDY PURPOSES ONLY COPYRIGHT © 2025 ALL RIGHTS RESERVED 1
,A. anneal the surface.
B. give better heat flow.
C. reduce oxidation.
D. pre-seal the oxidation. - ANSWER✔✔-C. reduce oxidation.
Outdoor condensing units that are installed in areas where flooding is possible must:
A. be mounted above flood level.
B. utilize NEMA 1 enclosures.
C. be mounted under an overhanging eave.
D. use water resistant components. - ANSWER✔✔-A. be mounted above flood level.
The component used to reduce sound transmission and prevent water leaks on a rooftop air
conditioner packaged unit installation is the:
A. curb gasket.
B. silicone caulk.
C. roof flashing.
D. roofing tar. - ANSWER✔✔-A. curb gasket.
FOR STUDY PURPOSES ONLY COPYRIGHT © 2025 ALL RIGHTS RESERVED 2
,Return air leakage in a hot attic will:
A. Increase capacity
B. Decrease capacity
C. Increase airflow
D. Decrease airflow - ANSWER✔✔-B. Decrease capacity
An air conditioner refrigerant circuit should be evacuated to a minimum of:
A. 0 microns.
B. 200 microns.
C. 500 microns.
D. 1200 microns. - ANSWER✔✔-C. 500 microns.
Which of the following substances could create an extremely dangerous condition if used to check
refrigeration system for leaks?
A. R-22
B. Nitrogen
C. Oxygen
FOR STUDY PURPOSES ONLY COPYRIGHT © 2025 ALL RIGHTS RESERVED 3
, D. Carbon Dioxide - ANSWER✔✔-D. Carbon Dioxide
The subcooling method for checking charge is generally used on air conditioners with what type of
metering?
A. Only externally equalized thermostatic expansion valves
B. Any thermostatic expansion valve
C. Piston type
D. Any fixed metering device - ANSWER✔✔-B. Any thermostatic expansion valve
Supply ducts running through unconditioned space should be insulated and have:
A. equal friction.
B. excessive air velocity.
C. a vapor barrier.
D. a transition backing. - ANSWER✔✔-C. a vapor barrier.
An important consideration when installing a motorized economizer is to check to be certain that:
A. the vanes are set for a maximum 10% outdoor air.
B. the vanes open on any call for cooling.
FOR STUDY PURPOSES ONLY COPYRIGHT © 2025 ALL RIGHTS RESERVED 4
2025 Questions and Answers
A system is supplied from the factory with charge of 5 pounds 10 ounces for a 15 foot line set. The
line set is 25 feet long. The manufacturer's instruction sheet specifies 0.6 ounces of refrigeration to
be added for each added foot of refrigerant line set length. What is the total refrigerant charge for
the system?
A. 6 ounces
B. 5 pounds
C. 5 pounds 10 ounces
D. 6 pounds - ANSWER✔✔-D. 6 pounds
15ft - 25ft = 10ft x .6 = 6 ounces
5 pounds + 10 ounces + 6 ounces
5 pounds + 16 ounces = 6 pounds
The purpose of using flux when soldering is to:
FOR STUDY PURPOSES ONLY COPYRIGHT © 2025 ALL RIGHTS RESERVED 1
,A. anneal the surface.
B. give better heat flow.
C. reduce oxidation.
D. pre-seal the oxidation. - ANSWER✔✔-C. reduce oxidation.
Outdoor condensing units that are installed in areas where flooding is possible must:
A. be mounted above flood level.
B. utilize NEMA 1 enclosures.
C. be mounted under an overhanging eave.
D. use water resistant components. - ANSWER✔✔-A. be mounted above flood level.
The component used to reduce sound transmission and prevent water leaks on a rooftop air
conditioner packaged unit installation is the:
A. curb gasket.
B. silicone caulk.
C. roof flashing.
D. roofing tar. - ANSWER✔✔-A. curb gasket.
FOR STUDY PURPOSES ONLY COPYRIGHT © 2025 ALL RIGHTS RESERVED 2
,Return air leakage in a hot attic will:
A. Increase capacity
B. Decrease capacity
C. Increase airflow
D. Decrease airflow - ANSWER✔✔-B. Decrease capacity
An air conditioner refrigerant circuit should be evacuated to a minimum of:
A. 0 microns.
B. 200 microns.
C. 500 microns.
D. 1200 microns. - ANSWER✔✔-C. 500 microns.
Which of the following substances could create an extremely dangerous condition if used to check
refrigeration system for leaks?
A. R-22
B. Nitrogen
C. Oxygen
FOR STUDY PURPOSES ONLY COPYRIGHT © 2025 ALL RIGHTS RESERVED 3
, D. Carbon Dioxide - ANSWER✔✔-D. Carbon Dioxide
The subcooling method for checking charge is generally used on air conditioners with what type of
metering?
A. Only externally equalized thermostatic expansion valves
B. Any thermostatic expansion valve
C. Piston type
D. Any fixed metering device - ANSWER✔✔-B. Any thermostatic expansion valve
Supply ducts running through unconditioned space should be insulated and have:
A. equal friction.
B. excessive air velocity.
C. a vapor barrier.
D. a transition backing. - ANSWER✔✔-C. a vapor barrier.
An important consideration when installing a motorized economizer is to check to be certain that:
A. the vanes are set for a maximum 10% outdoor air.
B. the vanes open on any call for cooling.
FOR STUDY PURPOSES ONLY COPYRIGHT © 2025 ALL RIGHTS RESERVED 4
