NATE AC SERVICE CERTIFICATION
QUESTIONS WITH COMPLETE 100%
VERIFIED SOLUTIONS 2024/2025, EXAMS
OF APPLIED MECHANICS
A system supply airflow check is used to diagnose:
A. humidity problems.
B. compressor overheating.
C. restricted liquid line drier
D. condenser fan motor overheating. Correct Answer A. humidity
problems.
A technician finds a R-410A system with the following:
*Suction pressure is 105 psi
*Suction line temperature is 75degF
*Recommended superheat is 20degF
This indicates the system:
A. is overcharged.
B. has excess airflow
C. is undercharged.
D. has low airflow Correct Answer C. is undercharged.
What effect does overcharging have on subcooling?
A. It depends on which type of refrigerant is used
B. It increases it
C. It decreases it
D. It depends on the metering device used Correct Answer *D It
depends on the metering device used
,When an air conditioner with a thermostatic expansion valve
installed is overcharged, the excess charge should be removed
by recovering some charge and checking:
A. system pressures.
B. superheat.
C. subcooling.
D. head pressure. Correct Answer *C. subcooling
With an R-410A condensing pressure of 397 psig and a liquid line
temperature of 108degF, what is the subcooling temperature?
A. 36degF
B. 24degF
C. 16degF
D. 8degF Correct Answer D. 8degF
What is the maximum acceptable supply voltage tolerance for a
120 V circuit?
A. +/-3%
B. +/-5%
C. +/-10%
D. +10% / -15% Correct Answer B. +/-5%
a compressor with proper voltage and a hard start relay and
capacitor draws lock rotor amps on startup. Which of the following
is most likely the problem?
A. The unit is overcharged.
B. The potential relay is open.
C. The start and run windings are open.
D. The pressure difference on the compressor is too great.
Correct Answer *B
,With the thermostat blower switch set to ON, which of the
following measurements indicates a call for residential indoor
blower operation?
A. 0 volts at the load side of the relay
B. 24 volts at the load side of the relay
C. 0 volts at the relay coil
D. 24 volts at the relay coil Correct Answer *B
A 120V x 24V step down transformer has a rating of 40 VA. This
transformer must not be connected to a load above what current
draw?
A. 0.3 amps
B. 0.6 amps
C. 1.7 amps
D. 3.0 amps Correct Answer C. 1.7 amps
What does a bright red or orange glow from the resistance
elements in a duct heater indicate?
A. Flow of air is insufficient.
B. Line voltage is insufficient.
C. Supply wires are oversized.
D. Duct heaters are operating properly. Correct Answer A. Flow
of air is insufficient.
During an annual service check up, it is discovered that there is a
moderate amount of resistance on a "bellyband" crankcase
heater. What does this condition indicate?
A. The crankcase heater will operate
B. Line voltage is insufficient.
C. Supply wires are oversized.
D. Duct heaters are operating properly. Correct Answer *A
, 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 Correct Answer *B
Will a Capacitor Start-Capacitor Run (CSCR) motor that has an
open run capacitor start?
A. No, it would be unable to start without the run capacitor
B. It may start, but it draws a higher than normal running current
C. Yes, it will start, but it will run backwards
D. It can only start if the voltage is higher Correct Answer *A
Which microfarad value indicates a good start capacitor rated at
145-175 mfd?
A. 130
B. 160
C. 180
D. 190 Correct Answer B. 160
What effect does insufficient voltage have on a solenoid valve?
A. It causes flash gas formation
B. The valve will operate normally
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