NATE AC SERVICE CERTIFICATION EXAM
250 UNIQUE PRACTICE QUESTIONS AND
ANSWERS WITH DETAILED RATIONALES
LATEST UPDATE
SECTION 1: SAFETY (Questions 120)
1. Which of the following substances could create an extremely dangerous
condition if used to check a refrigeration system for leaks?
A. R22
B. Nitrogen
C. Oxygen
D. Carbon Dioxide
Correct Answer: C
Rationale: Oxygen mixed with refrigerant oil under pressure can cause a violent
explosion. Never use oxygen or compressed air to pressure test or leak check a
refrigeration system. Use nitrogen or a trace gas with an electronic leak detector.
2. When brazing copper refrigerant lines, what safety equipment is essential?
A. Leather gloves only
,B. Safety glasses with shaded lenses (oxyacetylene goggles)
C. Dust mask
D. Hearing protection
Correct Answer: B
Rationale: Brazing produces intense bright light that can damage eyes. Shaded
safety glasses or oxyacetylene goggles are required to protect against ultraviolet
and infrared radiation. Leather gloves, fireresistant clothing, and adequate
ventilation are also recommended.
3. A technician is about to recover refrigerant from a system. Before connecting
hoses, what is the first safety step?
A. Open the recovery tank vapor valve
B. Put on safety glasses and gloves
C. Verify the recovery tank is rated for the refrigerant type
D. Power off the unit and verify with a meter
Correct Answer: D
Rationale: Electrical safety is paramount. Always deenergize the equipment and
verify with a meter that power is off before connecting hoses or accessing the
refrigerant circuit to prevent electrical shock.
,4. What is the maximum safe pressure for leak testing an R410A system with
nitrogen?
A. System nameplate lowside test pressure (typically 150250 psig)
B. 500 psig regardless of system
C. Manufacturer's specified maximum test pressure (often 400600 psig for high
side)
D. 1.5 times the critical pressure
Correct Answer: C
Rationale: Always follow manufacturer specifications for maximum test pressure.
For R410A systems, the highside test pressure is typically 400600 psig. Exceeding
rated pressure can rupture components, causing serious injury.
5. A technician is using a ladder to access a rooftop unit. The ladder should extend
above the roof landing at least:
A. 12 inches
B. 24 inches (2 feet)
C. 36 inches (3 feet)
D. 48 inches (4 feet)
Correct Answer: C
, Rationale: OSHA requires ladders to extend at least 3 feet (36 inches) above the
roof landing surface to provide a handhold for safe transition onto the roof.
6. What is the primary danger when using a torch near a refrigerant line that may
contain refrigerant?
A. Fire
B. Release of toxic gases
C. Explosion from pressurized refrigerant
D. Damage to the copper tubing
Correct Answer: C
Rationale: Heating a sealed refrigerant line containing liquid refrigerant can cause
rapid pressure buildup and violent rupture. Always ensure the system is completely
recovered and open to atmosphere before applying heat.
7. Which type of fire extinguisher should be used on an electrical fire in an HVAC
unit?
A. Class A
B. Class B
C. Class C
D. Class D
250 UNIQUE PRACTICE QUESTIONS AND
ANSWERS WITH DETAILED RATIONALES
LATEST UPDATE
SECTION 1: SAFETY (Questions 120)
1. Which of the following substances could create an extremely dangerous
condition if used to check a refrigeration system for leaks?
A. R22
B. Nitrogen
C. Oxygen
D. Carbon Dioxide
Correct Answer: C
Rationale: Oxygen mixed with refrigerant oil under pressure can cause a violent
explosion. Never use oxygen or compressed air to pressure test or leak check a
refrigeration system. Use nitrogen or a trace gas with an electronic leak detector.
2. When brazing copper refrigerant lines, what safety equipment is essential?
A. Leather gloves only
,B. Safety glasses with shaded lenses (oxyacetylene goggles)
C. Dust mask
D. Hearing protection
Correct Answer: B
Rationale: Brazing produces intense bright light that can damage eyes. Shaded
safety glasses or oxyacetylene goggles are required to protect against ultraviolet
and infrared radiation. Leather gloves, fireresistant clothing, and adequate
ventilation are also recommended.
3. A technician is about to recover refrigerant from a system. Before connecting
hoses, what is the first safety step?
A. Open the recovery tank vapor valve
B. Put on safety glasses and gloves
C. Verify the recovery tank is rated for the refrigerant type
D. Power off the unit and verify with a meter
Correct Answer: D
Rationale: Electrical safety is paramount. Always deenergize the equipment and
verify with a meter that power is off before connecting hoses or accessing the
refrigerant circuit to prevent electrical shock.
,4. What is the maximum safe pressure for leak testing an R410A system with
nitrogen?
A. System nameplate lowside test pressure (typically 150250 psig)
B. 500 psig regardless of system
C. Manufacturer's specified maximum test pressure (often 400600 psig for high
side)
D. 1.5 times the critical pressure
Correct Answer: C
Rationale: Always follow manufacturer specifications for maximum test pressure.
For R410A systems, the highside test pressure is typically 400600 psig. Exceeding
rated pressure can rupture components, causing serious injury.
5. A technician is using a ladder to access a rooftop unit. The ladder should extend
above the roof landing at least:
A. 12 inches
B. 24 inches (2 feet)
C. 36 inches (3 feet)
D. 48 inches (4 feet)
Correct Answer: C
, Rationale: OSHA requires ladders to extend at least 3 feet (36 inches) above the
roof landing surface to provide a handhold for safe transition onto the roof.
6. What is the primary danger when using a torch near a refrigerant line that may
contain refrigerant?
A. Fire
B. Release of toxic gases
C. Explosion from pressurized refrigerant
D. Damage to the copper tubing
Correct Answer: C
Rationale: Heating a sealed refrigerant line containing liquid refrigerant can cause
rapid pressure buildup and violent rupture. Always ensure the system is completely
recovered and open to atmosphere before applying heat.
7. Which type of fire extinguisher should be used on an electrical fire in an HVAC
unit?
A. Class A
B. Class B
C. Class C
D. Class D
