Modern refrigeration and air conditioning Ch. 17-20 Flashcards
What happens to the high and low side pressures during the off cycle?
They become equal.
Fast freezing preserves food better than slow freezing because…
Slower oxidation and foods form smaller water crystals (less damaging).
Refrigerator should be set to maintain product temperature of _____ or less
40°F (4.5°C)
What is the main advantage of a chest freezer compared to an upright freezer?
Efficiency! less cold air lost when lid is opened (cold air falls)
The evaporator in most refrigerator-freezers is located…
In the freezer compartment top of cabinet
In a refrigerator-freezer, the percentage of cold air that is delivered to the fresh-food compartment is controlled by the ______
Damper
The outer shell of a refrigerator-freezer is typically made from….
Sheets of steel
When closed, the refrigerator door seals tightly to the cabinet because of ________
small magnets in the gasket
Wine cooler doors are typically made of _____
Double-paned, tempered, safety glass
Is it common for a domestic refrigerator-freezer to contain some liquid refrigerant in the evaporator?
Yes.
What is the common evaporator temperature range in a domestic refrigerator-freezer?
0°F to -25°F (-18°C to -32°C)
most common compressor used in domestic refrigerators?
Split Phase
on start up a motor may draw an overload of up to __%
600%
poor air circulation in a natural draft condenser =
high head pressure, incresed run-time, and insufficient cooling.
hot wall condenser uses
tubing that is in direct contact with the outer wall of the cabinet which serves as a heat sink
forced draft condenser does…
takes air in from the front of the refrigerator and expells the air out of the back
cardboard partitions do what?
direct air flow
most common metering device in domestic refrigerators
capillary tube
what is the purpose of the filter drier
to prevent moisture from entering the metering device where it could freeze and cause clogging
what does the evaporator do
absorbs heat in the cabinet when refrigerant passes through it
what is the purpose of the heat exchanger between the capillary tube and suction line
to prevent liquid refrigerant to the compressor and to provide sub cooling to liquid refrigerant before it enters the evaporator
most common fixed temperature range in domestic refrigerators
37-41°f
semi automatic defrost
button must be pressed to begin defrost cycle and it automatically cycles back to normal run
automatic defrost
electric heating element next to evaporator with a timer operates during the off cycle
demand defrost
active based on number of times refrigerator is opened
continuous defrost
counts down to next defrost cycle no matter if compressor is running
timed defrost
uses a timer to set a predetermined time to defrost
mullion heater
electric heater installed arounf the door openings to prevent condensation from forming
flow of wate in automatic ice makers are regualted by
solenoid water valve
low water pressure can make ____ ice cubes
hollow
3 steps to automatic ice maker
fill, freeze, harvest
best method of cutting capillary tubing is…
making a notch with a file and bending the tubing back and forth
2 methods for crushed ice
auger and reverse auger
refrigerators should only be installed in rooms that are __ square ft or larger
100
there should be serveral large loops in refrigerator water line to?
move the refrigerator with out disconnecting the water connection
an extention cord may cause ?
an un exceptable voltage drop
hot wall condenser refrigerator must have atleast __” of air space
2
if a refrigerator does not start and the inside light does not come on what is most likely the problem
elecrical circuit
a leaky door gasket can cause …
build up of frost on the evaporator
what can prevent a newly installed ice maker from working properly
if the lice maker temp is held at 20 °f
compressor condition, storage space, and temperature outside of the cabinet affects what
freezer cycling time
over charge of refrigerant can result in
frost on the suctionline
a system has symptoms of restriction in the metering device but begins acting normally when heat is applied what is the most likely cause
moisture in the system
condenser and compressor should be cleaned atleast…
every three months
a vacuum with a brush attachment can be used to …
clean the compressor and condensor
in a compressor burn out ___ mixes with refrigerant and oil cause an odor
burnt electrical wiring
a filter drier on the high side should be installed at the
capillary tube inlet
a second filter drier on the low side will prevent what
repeat compressor burnout
indication a system is low on refrigerant
high low side pressure
oil should be replaced when?
in the event of a leak
when discarding a refrigerator you must
remove the doors, reclaim the refigerant, and place a label indicating the refrigerant has been reclaimed
