NATE AC SERVICE CERTIFICATION
COMPLETE ANSWERS GRADED A+
◉ Service site conditions are:
• House feels drafty in cooling
• 3 ½ ton split system
• High supply face velocities
• Ductwork is properly sized
• Total CFM 1400
What do these readings indicate?
A. the system is operating normally and there is nothing wrong
B. the returns are undersized
C. the system is operating normally but the supply registers are
too restrictive
D. the blower is set at too high a CFM
Answer: C. The system is operating normally but the supply
registers are too restrictive
(3 ½ X 400 = 1,400 cfm)
◉ What is an acceptable supply voltage tolerance for a 120V
circuit?
,A. +/- 3%
B. +/- 5%
C. +/- 10%
D. +10% / -15%
Answer: C. +/- 10%
◉ If an air conditioning system needs to operate in a low ambient
condition, the condenser may become too efficient. What happens
to condenser operation and what can be done to counteract this
condition?
A. the head pressure becomes too low and the superheat needs to
be lowered
B. the head pressure becomes too low and the superheat needs to
be raised
C. the head pressure becomes too low and the condenser fan
motor needs to be slowed or stopped
D. the suction pressure becomes too high and a low ambient
controller will lower it
Answer: C. The head pressure becomes too low and the condenser
fan motor needs to be slowed or stopped
◉ Which of the following is a likely problem if the air across the
evaporator of an air conditioner has a high temperature
differential?
, A. too much charge
B. clogged expansion valve
C. dirty filter or evaporator
D. moisture in the system
Answer: C. Dirty filter or evaporator
◉ What is the subcooling for an R-22 unit with a high side
pressure of 260 psig, a low side pressure of 68 psig, and a liquid
line temperature of 90°F?
A. 50°F
B. 30°F
C. 20°F
D. 12°F
Answer: B. 30°F
(260 psig = 120 degrees - 90 = 30 degrees)
◉ When performing a cycling check during a preventative
maintenance call, the technician should first check with the owner
of the equipment for their opinion of performance. The next step
is to turn the unit off at the thermostat SYSTEM switch. Next:
COMPLETE ANSWERS GRADED A+
◉ Service site conditions are:
• House feels drafty in cooling
• 3 ½ ton split system
• High supply face velocities
• Ductwork is properly sized
• Total CFM 1400
What do these readings indicate?
A. the system is operating normally and there is nothing wrong
B. the returns are undersized
C. the system is operating normally but the supply registers are
too restrictive
D. the blower is set at too high a CFM
Answer: C. The system is operating normally but the supply
registers are too restrictive
(3 ½ X 400 = 1,400 cfm)
◉ What is an acceptable supply voltage tolerance for a 120V
circuit?
,A. +/- 3%
B. +/- 5%
C. +/- 10%
D. +10% / -15%
Answer: C. +/- 10%
◉ If an air conditioning system needs to operate in a low ambient
condition, the condenser may become too efficient. What happens
to condenser operation and what can be done to counteract this
condition?
A. the head pressure becomes too low and the superheat needs to
be lowered
B. the head pressure becomes too low and the superheat needs to
be raised
C. the head pressure becomes too low and the condenser fan
motor needs to be slowed or stopped
D. the suction pressure becomes too high and a low ambient
controller will lower it
Answer: C. The head pressure becomes too low and the condenser
fan motor needs to be slowed or stopped
◉ Which of the following is a likely problem if the air across the
evaporator of an air conditioner has a high temperature
differential?
, A. too much charge
B. clogged expansion valve
C. dirty filter or evaporator
D. moisture in the system
Answer: C. Dirty filter or evaporator
◉ What is the subcooling for an R-22 unit with a high side
pressure of 260 psig, a low side pressure of 68 psig, and a liquid
line temperature of 90°F?
A. 50°F
B. 30°F
C. 20°F
D. 12°F
Answer: B. 30°F
(260 psig = 120 degrees - 90 = 30 degrees)
◉ When performing a cycling check during a preventative
maintenance call, the technician should first check with the owner
of the equipment for their opinion of performance. The next step
is to turn the unit off at the thermostat SYSTEM switch. Next:
