Commercial Refrigeration
Certification Questions and
Answers 100% Verified
"Pump down" means to capture system refrigerant in the:
A. recovery cylinder.
B. compressor.
C. condenser and/or liquid receiver.
D. suction accumulator. - ANSWER - C. condenser and/or liquid receiver.
A _____ is usually required for ultra-low temperature applications.
A. cooler
B. comfort cooling system
C. freezer
D. cascade system - ANSWER - D. cascade system
A _____ type metering device is best suited in applications where freeze protection is
required.
A. thermostatic expansion valve (TEV)
B. automatic expansion valve (AEV)
C. float
D. capillary tube - ANSWER - B. automatic expansion valve (AEV)
A customer calls and indicates that a walk-in freezer is running gradually higher box
temperature. The technician finds the box at 15°F, the thermostat is set properly for
a freezer application, and the condensing unit is operating, but not cycling after
adequate pull down time. An inspection of the evaporator reveals heavy ice
accumulated across the top two rows, and the entire body of the thermostatic
expansion valve and power element frozen in a bell of Ice. The technician decides to
advance the electromechanical defrost timer to the next defrost period and observe
the defrost function. In doing so, the evaporator defrosts to the level of the ice
,build-up, but no further. All power to both the freezer and condensing unit is
removed, locking and tagging each disconnect. The technician then defrosts the
remainder of the ice from the evaporator and expansion valve body. All evaporator
housings are placed back and sec - ANSWER - B. over a period of time, moisture had
gathered under the flare nut on the evaporator side of the expansion valve.
Repeated freezing and thawing had created enough force to damage the flare,
creating a slow refrigerant leak.
A defrost cycle is required whenever the evaporator must operate below:
A. 0°F
B. 32°F
C. 10°F
D. 20°F - ANSWER - B. 32°F
A dirty evaporator and subsequent low evaporator pressures will cause:
A. high compression ratios.
B. low compression ratios.
C. high head pressure
D. high suction pressure. - ANSWER - B. low compression ratios.
A customer calls and indicates that he has a walk-in freezer that is cutting on and
off after a very short run time on a repeated basis. He indicates that he had a higher
than normal power bill the previous month and thinks the unit's erratic behavior
may have contributed to the higher bill. The technician arrives and inspects the
freezer. The freezer box temperature is —10°F, and the condensing unit is off.
However, the technician observes the condensing unit operate and short cycle
several times within a few minutes of the demand being satisfied. The technician
shuts the unit down, locking and tagging the disconnect.
This system is equipped with both low and high pressure switches, a suction line
accumulator, and a liquid line solenoid. The technician notices that there is ice
build-up from the outlet of the liquid line solenoid to the expansion valve.
Manifold gauges are attached to the service ports. Removing t - ANSWER - C. the
liquid line solenoid is leaking during the off cycle, causing the low pressure switch to
cycle the condensing unit.
, A customer complains that their counter top ice machine is making a loud noise and
not producing any ice. Upon arrival, the technician removes the front panel and
determines that the noise is coming from the ice machine auger. Before the
technician can unplug the power supply, the auger drive motor overload opens and
the drive motor stops. The machine's compressor continues to operate.
The technician unplugs the ice machine and attaches gauges to the low and high
side service
ports. In addition, a clamp-on ammeter is placed on the power lead to the
compressor. The technician turns the power switch to the off position and plugs the
ice machine back into the power supply. The technician locates the manual reset
switch located on top of the auger drive motor and attempts to reset the switch.
The switch will not reset and the motor frame is very hot. Using ice from another
machine in a heavy plastic bag, the motor is coo - ANSWER - C. the lack of water
flow reduced evaporator load, which resulted in the auger freezing up and the drive
motor tripping the overload. The low pressure and current are the result of low load
on the evaporator. Water flow must be restored and the machine should operate
properly.
A customer is experiencing low ice production in a cube type ice machine.
Symptoms include long run cycle, thin or smaller cubes, and low production. The
initial visual inspection confirms the owner's complaint of thin ice and low
production. Further inspection reveals that the ice machine Is equipped with a
harvest solenoid and a thermostatic expansion valve. The water pump is operating
and the water reservoir is clean and free of debris. A check of the water
temperature in the reservoir is 32°F. The technician decides to install manifold
gauges and check system pressures. This Indicates slightly elevated suction
pressure with the discharge pressure at or near normal for the application and
refrigerant used. A check of evaporator superheat shows it to be 15°F to 18°F. A
check of temperature difference across the harvest solenoid indicates a
temperature rise of approximately 10°F. A check of condenser sub cooling ind -
ANSWER - D. the harvest solenoid ls leaking. keeping the suction pressure above
normal, and
must be replaced.
A customer reports that their low temperature reach-in freezer had a burned
compressor replaced last week by another service company, and now is not cooling
properly. When you arrive and examine the system, you find that the evaporator
seems to be starving for refrigerant. On inspecting the condensing unit, you notice
that the liquid line is sweating where it leaves the filter drier.
This is most likely the result of:
A. debris from the burned compressor has clogged the filter drier.
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