Modern Refrigeration and

1
Modern Refrigeration and Air Conditioning
Althouse Turnquist Bracciano
PowerPoint Presentation by Associated
Technical Authors
PublisherThe Goodheart-Willcox Company,
Inc.Tinley Park, Illinois
2
Chapter 11
Domestic Refrigerators and Freezers
3
Learning Objectives

• Discuss the construction of domestic
  refrigerators and freezers.
• Describe the refrigeration mechanical components
  and cabinets for different types of refrigerators
  and freezers.
• Compare standard circuit diagrams and ladder
  diagrams of a system.
• Discuss differences in circuits for manual
  defrost and automatic defrost systems.
• Demonstrate how to repair damaged cabinet
  finishes.

4
Learning Objectives

• Identify the various types of condensing units
  and evaporators used in domestic systems.
• Follow approved safety procedures.

5
Refrigeration System Parts

• A domestic refrigerator or freezer consists of
  three parts
• CabinetContains and supports evaporator and
  condensing unit.
• Refrigeration Mechanical ComponentsCondensing
  unit and evaporator.
• Electrical CircuitAll circuits, relays,
  overcurrent protection, etc.

6
Preserving Foods byRefrigeration and Freezing
11.1

• Foods last longer when kept at a temperature just
  above freezing.
• Lower temperatures
• Slow down oxidation
• Reduce multiplication of bacteria.
• Reduce evaporation in the food.

7
Cold Preserves Food
11.1.1

• Enzymes
• Cause food spoilage.
• Are slowed down by low temperatures.
• Are destroyed by pasteurization.
• Colloids
• Are found in flesh foods.
• Are cell containers if broken, food
  deteriorates.
• Low temperatures can slow colloidal changes.

8
Cold Preserves Food continued
11.1

• Fast freezing produces small ice crystals and is
  less damaging to food.
• Slow freezing allows time for larger crystal
  growth, increasing colloidal damage.

9
Storing Fresh Foodsin the Refrigerator
11.1.2

• Air in the refrigerator should be dry.
• Moisture in the refrigerator collects and
  condenses on the evaporator surfaces.
• Food containers should be covered and airtight.
• Cabinet temperature should be kept at 35ºF to
  41ºF (1.7ºC to 5ºC).
• Food and Drug Administration (FDA) requires a
  41ºF (5C) product temperature.
• At the above temperatures, fresh foods will last
  three days to a week.

10
Storing Frozen Foodsin the Freezer
11.1.3

• Air in a food freezer is very dry.
• Moisture in the air will condense on the
  evaporator surfaces.
• Food packages must be tightly sealed.
• Remove air from packaging prior to freezing.
• Hot foods should be allowed to cool prior to
  freezing.

11
Storing Frozen Foodsin the Freezercontinued
11.1.3

• Freezer burn is indicated by change in color or
  outside appearance of food.
• Frozen foods may be kept for several weeks at 0ºF
  to 10ºF (17.7ºC to 23.3ºC).
• Food to be kept for a year or more should be
  frozen at 20ºF (28.9ºC) or lower.

12
Refrigerator andFreezer Insulation
11.2

• Insulation
• Lines the walls or the refrigerator and freezer
  cabinet.
• Prevents heat from leaking through the walls into
  the cabinet.
• Urethane foam or fiberglass are commonly used
  insulators in household refrigerators and
  freezers.

13
RefrigeratorSingle Door, Manual Defrost
11.3

• A simple system, consisting of an evaporator
  inside the cabinet and a condensing unit.
• Evaporator may be placed across top of cabinet or
  in one of the upper corners of the cabinet.
• Condensing unit is located under or at the back
  of the cabinet.

14
RefrigeratorSingle Door, Manual Defrost
11.3
15
Cabinets
11.3.1

• Made of pressed steel with welded seams.
• Outer shell must be smooth and vaporproof.
• Inner shell provides brackets for mounting
  shelves, lights, etc.
• Insulation is installed between the outer and
  inner shells.
• Light switch is located at hinge side of the
  door turns light on and off as door is opened
  and closed.
• Plastic trim piece (cold ban) is used at the
  door opening to reduce heat flow.

16
Mechanical Components
11.3.2

• Mechanical components of a simple refrigerator
• Hermetic CompressorIn the cabinet base.
• CondenserAt the bottom or back of the cabinet.
• EvaporatorInside the cabinet.

17
Mechanical Components continued
11.3.2

• Liquid refrigerant enters evaporator.
• Refrigerant boils absorbing heat in the
  evaporator.
• Vapor is drawn through the suction line to the
  compressor.
• In the compressor, vapor is compressed to a high
  pressure and temperature.
• Compressed vapor flows through the high-pressure
  vapor line into the condenser.
• In condenser, high-pressure, high-temperature
  vapor gives up heat to surrounding air.

18
Mechanical Components continued
11.3.2

• Vapor is condensed back to a liquid.
• Liquid refrigerant flows through the
  filter-drier.
• It enters the capillary tube.
• Warm refrigerant gives up some of its heat to the
  cold suction line vapor, increasing the superheat
  of the vapor entering the compressor.
• Low-pressure liquid enters the evaporator and the
  cycle is repeated.

19
Mechanical Components
11.3.2
20
Manual DefrostDomestic Refrigerator
11.4

• Turn off refrigerator overnight. Use a drip pan
  to catch the condensation from defrosting.
• Turn refrigerator off and place a pan of hot
  water near the evaporator.

Caution Never use a metal scraper on an
evaporator. There is danger of puncturing it!

• Each time unit is defrosted, use baking soda and
  water to clean evaporator and inner
  refrigerator surfaces.

21
Electrical Circuits
11.4.3

• Electrical supply fed through the grounded
  service cord and plug.
• Two circuits are provided from the panel-mounted
  disconnect.
• One circuit is the cabinet light, controlled by
  cabinet switch.
• Second circuit is to motor compressor.
• Thermostat is in series with the second circuit
  and controls the compressor.

22
Electrical Circuits
11.4.3
23
Refrigeration Electrical Cycle
11.4.3

• Cabinet temperature reaches a predetermined
  point.
• Thermostat completes the circuit through the
  motor.
• Compressor runs and refrigeration cycle begins.
• Temperature inside cabinet reaches desired point.
• Thermostat turns off the current and the motor
  compressor stops.

24
Additional Electrical Devices
11.4.3

• Perimeter Drier
• Electrical resistance (heating) wire located in
  trim of freezer door.
• Operates constantly.
• Provides warming effect to halt condensation on
  the exterior of cabinet and around the freezer
  compartment door.

25
Additional Electrical Devicescontinued
11.4.3

• Ambient Compensator
• Electrical resistance (heating) wire.
• Provides continuous small heat flow into
  refrigerator compartment.
• Causes the refrigerator to cycle if the ambient
  room temperature drops below the normal
  thermostat setting.
• Attached to refrigerator compartment thermostat.
• Energized only on the off cycle.

26
Motor Control Circuit
11.4.3

• Starting relay connects both the starting winding
  and the running winding to the power circuit.
• Disconnects the starting relay and starting
  winding when compressor motor reaches 75 running
  speed.
• Starting relay provides overload protection for
  the motor.
• Overload protector contains resistor in series
  with the running current.
• If current draw is too great, bimetal contactor
  will break the circuit.

27
Motor Control Circuit
11.4.3
28
Automatic DefrostRefrigerator-Freezer
11.5

• Air in contact with evaporator surface below
  freezing temperature will cause moisture to
  condense and form ice on the evaporator.
• Refrigerator and freezer evaporator must be
  defrosted to maintain efficiency.
• Most refrigerators provide a system for automatic
  defrosting.
• Hot gas defrost uses solenoid valves. Heat from
  vapor in compressor discharge line and condenser
  are used for evaporator defrosting.
• Electric heaters may also be used to melt ice on
  evaporator surfaces.

29
Electric HeaterAutomatic Defrost
11.5.1

• Frost-free or no-frost-cycle refrigerators have
  the evaporator located outside the refrigerated
  compartment.
• While running, air is drawn over evaporator.
• This air is forced into the freezer and
  refrigerator compartments by a motor-driven fan.
• During the off cycle, evaporators automatically
  defrost.
• Evaporator condensation is carried to an
  evaporating pan. Heat from the compressor
  evaporates this moisture into the rooms
  atmosphere.
• There is never any visible frost accumulation.

30
Mechanical Components
11.5.1

• May provide multiple temperatures in refrigerator
  with a freezer compartment.
• EvaporatorRefrigerant evaporation provides heat
  absorption (cooling).
• Motor driven fan forces air over evaporator and
  through the ducts, providing all necessary
  refrigerator temperatures for the compartments.
• Motor CompressorSuction line from evaporator
  extends down to the inlet side of hermetic motor
  compressor in cabinet base.

31
Mechanical Components
11.5.1
32
Mechanical Components continued
11.5.1

• CondenserWire and tube type. Forced air
  circulation provided by a motor and fan located
  at back of the compartment containing compressor
  and condenser.
• Capillary TubeRefrigerant is condensed in
  condenser and flows through high-side
  filter-drier into capillary tube.
• Capillary tube is attached to section of suction
  line, providing a heat exchange between the two
  components.
• Refrigerant flows into evaporator, completing the
  cooling cycle.

33
Mechanical Components continued
11.5.1

• Several heating devices are used as driers.
• Electric resistance heater controlled by a timer
  automatically defrosts evaporator.
• Temperatures of cabinet regulated by temperature
  control.
• Electricity fed through grounded service cord and
  plug.
• Machine compartment connector block provides
  electrical connections to many components.

34
Hot Gas Automatic Defrost
11.5.2

• Accomplished through use of solenoid valves.
• Heat from vapor in discharge line and condenser
  used to defrost the evaporator.
• CabinetDefrost timer and solenoid valve housed
  in cabinet base.
• May use perimeter hot tube (drier) to provide
  heat and prevent condensation.

35
Hot Gas Automatic Defrost
11.5.2
36
Mechanical Components
11.5.2

• Two evaporators are used one in freezer
  compartment and one in refrigerator compartment.
  Refrigerant (both liquid and vapor) leaves
  freezer evaporator and flows into refrigerator
  evaporator.
• Motor CompressorVapor is drawn back to
  compressor, compressed and discharged into
  water-evaporating plate and coil assembly.
  Moisture is evaporated, and compressed vapor
  flows through oil cooler line in bottom of
  compressor.
• CondenserVapor then flows to vertical
  wire-and-tube condenser. Heat is given off.
  Compressed vapor returns to liquid state and
  flows through the filter-drier.

37
Mechanical Components continued
11.5.2

• Capillary TubeLiquid flows into capillary tube
  that is soldered to suction line, serving as a
  heat exchanger. Temperature of liquid refrigerant
  is reduced and superheat of vapor in suction line
  is increased. Refrigerant enters freezer
  evaporator at reduced pressure, evaporates,
  absorbs heat from inside of cabinet, and
  completes the cycle.

38
Hot Gas Defrost
11.5.2

• Solenoid valve opens and hot gas defrost cycle
  begins.
• Vapor from evaporators is drawn into compressor.
• It discharges into the water evaporating plate,
  heating the surface.
• Hot compressed vapor flows through the drain sump
  bypass line and flows into the freezer
  evaporator.
• Vapor flows into the refrigerator compartment
  evaporator through the accumulator.
• It flows back into the suction side of the
  compressor.

39
Hot Gas Defrost
11.5.2
40
Defrost Timer
11.5.2

• Controls the solenoid defrost valve.
• Driven by a self-starting electric motor which is
  geared to turn the shaft slowly.
• Completes one revolution every eight hours of
  compressor operation.
• When timer opens solenoid valve, defrost cycle
  continues for 17 minutes.
• Solenoid valve then closes and refrigerating
  cycle resumes.

41
Electrical
11.5.2

• Grounded service cord and plug supply
  electricity.
• Supply then goes to panel-mounted disconnect from
  which various circuits are fed.

42
Electrical
11.5.2
43
Frost FreeRefrigerator-Freezer
11.6.1

• May be fresh food on top and freezer on bottom.
• Evaporator is in upper back part of cabinet.
• Condenser is along lower back section.
• Fan moves cold air from freezer evaporator into
  the refrigerator compartment.
• Second fan circulates room air through cabinet
  bottom and over condenser.
• Doors are held shut by magnets.

44
Frost FreeRefrigerator-Freezer
11.6.1
Fans are used on both the condenser and
evaporator.
45
Electrical Circuits
11.6.3

• Electricity supply fed through grounded service
  cord and plug.
• Two electrical resistance (heating) elements in
  cabinet.
• Evaporator defrost is electrically heated.
• Note resistance of electrical components
  indicated in ohms.

46
Electrical Circuits
11.6.3
47
Frost-Free, Side-by-SideRefrigerator-Freezer
11.7

• Dispensers for water, crushed ice, etc., are
  built into the door.
• May have electronic monitor consoles that control
  all accessories and electrical current.

48
Questions

• Within what temperature range should the
  refrigerated cabinet be kept?

35ºF to 41ºF (1.6ºC to 5ºC)

• Within what temperature range should frozen foods
  be kept?

0ºF to 10ºF (17.8ºC to 23.3ºC)

• Where is the condensing unit located on a
  refrigerator?

Under or at the back of the cabinet.

• What is the state of the refrigerant as it flows
  through the discharge line to the condenser?

High-pressure superheated vapor.
49
Questions

• What happens to the refrigerant as it flows
  through the condenser?

Under high-side pressure, it changes from a gas
to a liquid and gives up heat to the surrounding
air.

• The thermostat is in ________ compressor circuit.

series

• Where is the perimeter drier located? What is its
  purpose?

It is located around the perimeter of the freezer
door and it prevents the formation of
condensation.
50
Questions

• What is the purpose of the start relay that is
  located on the compressor?

It disconnects the starting winding from the
circuit at 75 of motor running speed.

• Name two types of heat sources used to defrost an
  evaporator coil on a domestic refrigerator.

Electric and hot gas.
51
Questions

• Where is the hot gas solenoid placed in the
  refrigeration circuit?

Between the discharge line and the inlet to the
evaporator.

• Why is the capillary tube attached to the suction
  line?

It provides a heat exchanger, keeping the
refrigerant in the liquid state.

• What component controls the operation of the
  electric defrost heater and the hot gas solenoid?

The defrost timer.
52
CabinetsGeneral Electric
11.7.1

• Side-by-side refrigerator-freezer.
• Provides automatic ice and water dispenser
  controlled by electronic monitor.
• Temperature controls for both compartments at top
  or refrigerator compartment.
• Refrigerator compartment defrosts during every
  off cycle.
• Freezer defrosts (25 minutes) after six-hour
  accumulated compressor running time.

53
CabinetsGeneral Electric
11.7.1
54
Mechanical ComponentsGeneral Electric
11.7.2

• Evaporator, compressor, and condenser at back of
  freezer.
• Fan circulates air over condenser.
• Air enters and leaves through bottom grille.
• Dampers control flow of very cold air from
  evaporator in freezer compartment to refrigerator
  compartment.

55
Mechanical ComponentsGeneral Electric
11.7.1
Air flow in a frost-free, side-by-side
refrigerator-freezer.
56
ControlsGeneral Electric
11.7.2

• Refrigerant control is accomplished through use
  of a capillary tube. The tube is attached to
  suction line.

57
ControlsGeneral Electric continued
11.7.2
Electronic control console with touch pads is
located at front of freezer door.
58
ControlsGeneral Electric continued
11.7.2

• Diagnostic code will flash on control console
  when abnormal conditions exist. If more than one
  code function requires service, codes will be
  presented in order of priority.
• Electronic control console is connected to the
  wiring in the system.

59
Electrical CircuitsGeneral Electric
11.7.3

• Grounded service cord and plug supply
  electricity.
• Color-coding locates the wire going to each of
  the electrical circuits.
• Automatic ice maker controls plug into an ice
  maker receptacle for ease of service.
• Contains a wiring harness that allows any circuit
  to be worked on since wiring is not foamed in
  place.

60
Electrical CircuitsGeneral Electric
11.7.3
61
CabinetAmana
11.7.4

• Refrigerator compartment on right and freezer on
  the left.
• Center door on left side contains an external
  automatic dispensing unit for ice cubes and water.

62
Mechanical ComponentsAmana
11.7.5

• Evaporator is behind freezer compartment.
• Compressor and condenser are at bottom of
  compartment.
• Air circulates over condenser by fan and leaves
  through bottom grille.
• Fan on evaporator circulates very cold air in
  freezer.
• Dampers allow some of this very cold air to flow
  into the refrigerator compartment.

63
Mechanical ComponentsAmana
11.7.5
64
Mechanical ComponentsAmana continued
11.7.5

• A capillary tube attached to the suction line is
  the heat exchanger.
• Defrost occurs automatically after every six
  hours of compressor running time. The heater
  circuit then opens and runs for approximately 28
  minutes.

65
Electrical CircuitsAmana
11.7.6

• Wiring is located in foamed-in-place insulation.
• Numerous heaters are used in the system.
• The auxiliary heater is foamed-in-place and may
  be connected to the circuit if needed.
• Power-saver switch may be turned off if operating
  in extremely low-humidity areas.
• Ice maker controls are plugged into an ice maker
  receptacle.

66
Solid-State Ice Maker
11.8

• Solid-state controls may be used for automatic
  ice cube maker.
• These controls are assembled into a single
  printed circuit board.
• Inputs (existing conditions such as ice level,
  temperature, power) are fed into the circuit
  board through an edge connector.
• Outputs (motor power, switch signals) are also
  fed through the edge connector.

67
Solid-State Ice Maker continued
11.8

• Circuitry requires two types of voltages
• Low voltage DC signals operate semiconductor
  devices.
• A 120VAC line voltage operates the drive motor
  and water valve.
• A thermistor located in front of the ice cube
  tray monitors the temperature at that location
  and sends a signal to the solid-state control
  circuit. This triggers a relay that completes the
  circuit to drive the motor.
• A cam gear mechanism provides ice ejection.
• Switches control the motor and water valve and
  control and monitor the ice ejection process.

68
Chest-Type Freezers
11.9

• AdvantageLittle air change when cabinet is
  opened.
• Some manual defrost models may require defrosting
  once or twice per year.

69
Chest-Type Freezers continued
11.9

• To defrost
• Unplug condensing unit and remove stored food.
• Place bucket of hot water inside. With cabinet
  closed, ice will melt and drop away. Most have
  a drain for evacuation of water.
• Wipe remaining moisture with a solution of
  baking soda and water.

• Caution Never leave a freezer open or unlocked!
  When unattended, chest-type freezers should
  remain locked.

70
Cabinet, Mechanical Components, and Electrical
CircuitsFrigidaire
11.9.1

• Outer and inner shells are metal.
• Evaporator surrounds the inner liner and is
  attached to it.
• Condenser is attached to inside of outer shell.
• Hermetic compressor is used.
• Manually defrosted. Condensate (water) flows
  through drain system on bottom or side of cabinet.

71
Cabinet, Mechanical Components, and Electrical
CircuitsFrigidaire
11.9.1
72
Refrigeration Cyclefor Chest-Type Freezer
11.9.1

• Liquid refrigerant flows through capillary tube
  into the evaporator. There refrigerant evaporates
  and cools. Compressor draws vaporized refrigerant
  and pumps it into the pre-cooler condenser on
  back freezer wall. Here it releases part of its
  latent heat of vaporization and sensible heat of
  compression.
• From precooler condenser, refrigerant passes
  through oil cooling coil in compressor dome.
  Additional heat is picked up from the oil.
  Compressed vapor flows back to main condenser.
  Additional heat is released to atmosphere.
  Refrigerant condenses from a high pressure vapor
  to a high-pressure liquid.

73
Refrigeration Cyclefor Chest-Type Freezer
continued
11.9.1

• Condenser tubes are in contact with outer shell.
  Heat from condenser passes into outer shell
  preventing sweating. Liquefied refrigerant
  collects in bottom of condenser tubing. It flows
  into the filter-drier, moves into the capillary
  tube, and into the evaporator. The cycle repeats.

74
Refrigeration Cyclefor Chest-Type Freezer
11.9.1
75
Cabinet, Mechanical Components, and Electrical
CircuitsAmana
11.9.2

• Chest-type freezers are available in capacities
  from7 ft3 to 28 ft3.
• Evaporator surrounds the inner metal lining and
  is attached to it.
• Accumulator holds the liquid refrigerant until it
  is entirely evaporated.
• The accumulator outlet is at the top and leads to
  the suction line.

76
Cabinet, Mechanical Components, and Electrical
CircuitsAmana
11.9.2
77
Cabinet, Mechanical Components, and Electrical
CircuitsAmana
11.9.2

• Condenser attached to inside of the outer shell,
  completely surrounding the cabinet.
• Note the precooler that zigzags across the back
  of the cabinet down to the compressor.

78
Cabinet, Mechanical Components, and Electrical
CircuitsAmana continued
11.9.2

• Electrical power is supplied through a grounded
  three-prong service plug and cord.
• Note the warning light. It indicates whether the
  electrical circuit is hot, not whether cabinet
  temperature is satisfactory.

79
Upright Freezers
11.10

• Makes storage and removal of frozen food
  convenient.
• Similar in construction to a refrigerator-freezer,
  but insulation is heavier and motor control is
  different.

• Caution Never leave a cabinet-type freezer
  unlocked or unattended!

80
Cabinet, Mechanical Components, and Electrical
CircuitsFrigidaire
11.10.1

• Outer and inner shells are enameled steel.
• Evaporator is located at bottom of cabinet.
• Wraparound condenser located inside the outer
  shell on sides, back, and top.

81
Cabinet, Mechanical Components, and Electrical
CircuitsFrigidaire continued
11.10.1

• Automatic defrost cycle activated every 12 hours
  of operation.
• Evaporator (9) is located in upper third of
  cabinet. Capillary tube carries liquid
  refrigerant from the filter-drier (2), to the
  evaporator.
• Capillary tube (8) is soldered to suction line
  (11), forming a heat exchanger (10).

82
Cabinet, Mechanical Components, and Electrical
CircuitsFrigidaire continued
11.10.1

• Liquid refrigerant enters the evaporator and
  absorbs heat.
• A fan draws the cold air from bottom of cabinet
  through the evaporator, forcing air to the top of
  the freezer.
• This air is then discharged at the top of the
  refrigerated space.
• Cold air flows down this space and is drawn back
  up to the evaporator by the fan.

83
Cabinet, Mechanical Components, and Electrical
CircuitsFrigidaire continued
11.10.1

• A precooler condenser (3 and 6) runs from the
  compressor along the back shell or the cabinet
  and returns to the compressor (5).
• Refrigerant flows into the oil-cooling coil in
  the compressor dome (1). Here, the refrigerant
  picks up additional heat from the oil.

84
Cabinet, Mechanical Components, and Electrical
CircuitsFrigidaire continued
11.10.1

• Refrigerant vapor is pumped through the main
  condenser (4), where remaining heat is released
  to the atmosphere. Refrigerant is condensed to a
  liquid and flows by gravity to filter-drier and
  capillary tube. The cycle repeats.
• Condenser is attached to outer shell, warming it
  slightly and preventing sweating of the shell.

85
Cabinet, Mechanical Components, and Electrical
CircuitsFrigidaire continued
11.10.1

• All mechanisms and the cabinet are grounded.

86
Cabinet, Mechanical Components, and Electrical
CircuitsWhirlpool
11.10.2

• Cabinet is similar to single-door refrigerator.
• Evaporator on a manual defrost unit is usually
  part of cabinet shelves.
• No-frost systems use an evaporator located behind
  a baffle.
• Fan circulates air through the evaporator and
  then through the food section.
• Mechanical components include a motor compressor
  designed for low evaporator pressures and a
  forced-convection condenser with supply and
  return grilles.

87
Cabinet, Mechanical Components, and Electrical
CircuitsWhirlpool continued
11.10.2

• Wiring diagram for a manual-defrost upright
  freezer.
• Note stile heater and signal light that indicates
  power is on.
• Condenser and motor compressor should be wiped
  clean at least every six months.

88
Ice Accumulationin Cabinet Insulation
11.12

• Ice build-up will reduce insulating ability of
  the cabinet and cause unit to run more.
• Ice accumulation in freezer indicated by cold
  spot or condensation on outside surface. Shut off
  the freezer and allow it to warm up for a few
  days.
• May be due to air leak in outer casing (shell).
  Allows moisture to enter and condense in the
  insulation.
• If cold spots or condensation continue to appear,
  remove breaker strips and insert lightly packed,
  fine fiberglass to fill air pockets.

89
Cabinet Hardware
11.14

• Cabinet hinges usually use ball or nylon bearings
  requiring little or no lubrication. The hinges
  are usually adjustable.

• For child safety, federal law requires
  refrigerator cabinets be designed to be
  opened from the inside with no more than a 15
  lb. force. Today, most refrigerators use
  magnets to hold the door shut.

90
Cabinet Hardware continued
11.14

• Cabinets should be carefully leveled and adjusted
  so doors weight swings it closed from any
  position.
• Many units are mounted on rollers that usually
  adjust and can also be used to level the unit.

91
Cabinet Hardware continued
11.14

• Breaker strips (usually made of plastic) connect
  the metal outer shell to the metal liner where
  the cabinet contacts the door.
• A wide-blade putty knife wrapped with tape may be
  inserted to remove the outer edge of the breaker
  strip.

92
Questions

• What is used to move the cold freezer air to the
  refrigerated space?

Dampers.

• When must a power saver control be de-energized?

When the humidity is low.

• What type of control triggers a relay to cause
  the drive motor to operate on an ice maker?

A thermistor.

• How often must a manual defrost refrigerator be
  defrosted?

Once or twice per year.
93
Questions

• What is the purpose of the precooler on the
  condenser?

It cools refrigerant oil.

• Where is an accumulator located on a refrigerator?

In the suction line before the compressor.

• What is the purpose of an accumulator?

It prevents liquid floodback to the compressor
during the run cycle.
94
Cabinet Gaskets
11.15

• Door gaskets are usually made of flexible vinyl.
• Air leakage through the gasket will increase wear
  on unit and increase operating costs.

• Check door seals using a .003" thick plastic
  feeler gauge or a thin piece of paper. Insert
  the gauge or paper at several places around
  door opening. It should require a little pull on
  the gauge if gasket is properly fitted.

95
Cabinet Gaskets continued
11.15

• To check door gaskets
• Open refrigerator door halfway, noting effort
  required to open it.
• Leave door open 10 seconds.
• Close door and leave it closed 15 seconds.
• Open door and note effort required.
• It should require more effort to open the door
  the second time.
• On some refrigerators, the hinges may be adjusted
  to correct a poorly fitted gasket.

96
Cabinet Thermometers
11.17

• Recommended temperature range for a refrigerator
  compartment is between 35ºF (1.7ºC) and 45ºF
  (7.2ºC). Recommended temperature range for the
  freezer compartment is 0ºF to 10ºF (17.8ºC
  to23.3ºC).
• Thermometers can be used to monitor cabinet
  temperatures.

97
Safety
11.18

• Carefully handle refrigerators and freezers to
  avoid damage to the cabinet or mechanical
  components or injury.
• Do not place your hands near revolving fans.
• Always disconnect electrical power before working
  on system electrical parts. Open the switch or
  pull the plug to prevent potentially fatal
  shocks.
• Electrical systems must be grounded properly to
  the receptacle if an approved three-wire grounded
  plug is not used.

98
Safety
11.18

• Frost and ice should be removed by heating with
  hot water. Never use pointed or sharp metal tools
  to remove ice. They may puncture the
  refrigerating unit.
• If a refrigerator or freezer is taken out of
  service, the door must be removed immediately! Do
  not allow an out-of-service refrigerator stand
  where children may play in it. Suffocation can
  occur inside the cabinet in only a few minutes!
• Always lock chest and upright freezers!

99
Glossary

• ambient compensator
• Electronic device that provides a small amount of
  heat to the refrigeration compartment, ensuring
  machinery continues to cycle when ambient
  temperatures are low.
• perimeter drier
• Electrical resistance heat wire located in
  freezer door to prevent condensation on the
  exterior of the cabinet and around the freezer
  door.