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How Does Domestic Refrigerator Work: A Complete Guide - Part 2

Working of Domestic Refrigerators: Chapter 2


Defrost Systems


In this module, we will learn the defrost system used in refrigerators. Skip to quiz!!


Defrost Systems


Recall that the temperature in a refrigerator's freezer section is close to or lower than 0°C (32°F). Moisture present in the air inside a room freezes when it comes in contact with the evaporator coil of a refrigerator. This will form a frost layer on the evaporator coil.


The thick layer of frost deposited on an evaporator coil restricts the flow of air passing over that coil. This will also reduce heat transfer between the air and evaporator coil. The frost will not allow air to circulate from the freezer to the fresh food section.


Defrosting is the process of removing the ice or frost from an evaporator or freezer. The image to the right shows a defrosted evaporator coil and frosted evaporator coil.


Defrosting is an essential part of our refrigerator maintenance checklist, as frost adversely affects cooling performance. There are several defrosting techniques. These include:

  • Manual defrost,

  • Semi-automatic defrost, and

  • Automatic defrost.

Manual defrosting can be done by turning off a refrigerator. As we turn off a refrigerator, the refrigeration cycle stops. The cooling coil temperature rises to room temperature, thus allowing the frost to melt away.


The manual defrost system is not used in modern refrigerators. This is because it becomes tiresome to defrost a refrigerator manually.


In a semi-automatic defrost system, we need to push a button near the freezer to activate the defrosting function. This will turn off the compressor. A refrigerator will turn on automatically after defrosting is completed.


In the semi-automatic defrost system, the manufacturer sets the defrosting time. It’s brand-specific and can vary for every refrigerator. When we defrost manually, the defrost time is set by us and requires more attention.


We need to defrost the refrigerator manually every three days. An automatic defrost system does not require human intervention. An automatic defrost system prevents the formation of frost by activating an internal heating system.


A heating system directs heat to the cooling coil. This heat will melt the frost on the cooling coil. This defrost procedure is applied periodically by stopping the system. The automatic defrost takes one defrost cycle to complete.


Recall that a solenoid valve controls the flow of refrigerant depending on the electrical signals it gets. During a defrost cycle, a solenoid valve interrupts the refrigerant flow to the evaporator. This will ensure that refrigerant in the evaporator does not get heated.


Then, the electrical heating elements are energized, and the evaporator fan blows hot air over the evaporator coil. This melts the ice accumulated during the refrigeration cycle.


A defrost cycle occurs every eight hours in an automatic defrost system. Most of the time, a refrigerator may not need to go into defrost every eight hours.


The time between two defrost cycles depends on several factors. These include:

  • How many times we have opened the doors, and

  • How long the compressor has run.

Instead of turning on an energy-consuming heater every eight hours in modern refrigerators, we can use adaptive defrost control. Adaptive defrost control (ADC) is what makes refrigerators energy efficient. It varies the length of time it takes a machine to start defrosting.


An adaptive defrost control uses a control board to vary the time interval between defrost cycles. We’ll look into each control component of this defrost system in a later module.


Adaptive defrost control (ADC) will continually adjust the defrost intervals based on the following:

  • Number of door openings,

  • Compressor run time, and

  • Time passed after the last defrost cycle.

Recall that the moisture present in air freezes when it comes in contact with an evaporator coil. Outside humid air enters a fridge every time its door is opened. This increases the frost load. An ADC will adjust the time between defrost cycles to match the change in the frost load.


ADC will function the same way by monitoring the last defrost cycle. For example, if a defrost cycle duration is longer, it indicates a light frost buildup. Then, an adaptive defrost control will increase the time for which a system and compressor run.


Similarly, if the defrost cycle duration is shorter, it indicates a heavier frost buildup. An adaptive defrost control will decrease compressor run time between the defrost cycles by two hours.



Drain Lines


During a defrost cycle, ice melts to form water. This water flows down through the interior walls at the back of a fridge. We use a tube to carry this water called a drain line. The water goes through a drain line to the bottom of the refrigerator cabinet.

A drain pan collects the water that flows out of a fridge. A drain pan is a water tray that collects and stores water. The water then evaporates into the air.


Defrosting is the process of removing ice or frost from an evaporator or freezer. Defrosting techniques are:

  • Manual defrost,

  • Semi-automatic defrost, and

  • Automatic defrost.

Adaptive defrost control (ADC) is what makes refrigerators energy efficient. A drain pan is a water tray that collects and stores water.


 

Additional Systems


In this module, we will learn additional systems used in a refrigerator. Skip to quiz!


Dispensers


When it comes to side-by-side and french door refrigerator models, they are equipped with a dispenser system. This dispenser system consists of:

  • Water dispenser, and

  • Ice maker.

The new and improved models have dispensers built into the door. The commonly offered features of refrigerator dispensers are:

Let’s discuss each of these dispenser systems in detail.


Water Dispensers


A water dispenser is a device for supplying chilled water. It provides us clean filtered drinking water.


The water supplied by a dispenser system is filtered using a water filter. A simple carbon filter treats the drinking water dispensed from a refrigerator. This removes chlorine, fluorine, and other harmful impurities from the water.


Because of the water dispenser, we don’t need to fill water bottles or check their amount. We can press a button to get cold water immediately.


The water for a dispenser system in a refrigerator is supplied by one of the following means:

  • Water supply line connected to the refrigerator, or

  • Manually filling the dispenser water tank.

Recall that a flexible hose can bend as needed. A dispenser is connected to the water supply system using a flexible hose.


A flexible hose connected to a building’s main water supply fills the reservoir automatically. If a connection to the water supply is not possible, then water is poured into the tank manually.


A water dispenser makes cold water the same way a refrigerator makes its compartments cold. Recall that refrigerant boils off in an evaporator by absorbing heat from refrigerator compartments. In the case of a dispenser, heat is absorbed from the water tank to get chilled water.


When we press the water dispenser lever in the front of a refrigerator, it activates a switch in the refrigerator's door. This switch opens a valve in the back of the appliance. This allows water to flow through tubing into a water reservoir where it’s dispensed.



Ice Makers


Recall that we use the freezer section to make ice cubes in older refrigerators. We have to manually keep ice trays filled with water inside a freezer in these old systems. An icemaker automates the process of pouring water and extracting ice cubes from an ice tray.


Mechanical, electrical, and control components make ice-making automated. We’ll look at control and electrical components in a later module.


The mechanical components present inside an ice maker unit are:

  • Ice tray,

  • Ice bucket auger, and

  • Ice crusher blade.

Let’s learn about each of them.


Ice trays are also called ice molds. The water from a supply line fills the mold of an ice tray every cycle. Once the water freezes, a control device turns on a heater to loosen the ice from the mold.


An auger is a metal shaft with a blade that scrapes or cuts hard material. As an auger motor rotates, the ice bucket auger turns and lifts loose ice from an ice tray. Ice cubes are then released and dumped into a storage container in the freezer.


Ice crusher blades are blades for chopping ice. We use a rotating blade and a stationary blade for chopping ice.


Ice crusher blades are located inside ice crusher housing. They are mounted on an auger shaft. As an auger motor begins to rotate, ice gets trapped between these blades to crush it.


We can see how the mechanical components work to automate this process. At the beginning of a cycle, an electrical signal is sent to a water valve to fill the ice mold with water. Then, the freezer starts freezing the water.


After ice cubes have been created, a heating coil is activated to loosen them from their trays. The ice bucket auger then pushes them out of the trays. When we press the lever or button of a built-in ice maker, we get ice cubes.


We also need crushed ice to make mojitos on a hot summer day. When we press the crushed ice button on our refrigerator door, ice cubes are trapped between two sets of blades. These blades chop the ice cubes to be crushed in seconds.


The video shows how to operate a dispenser to get chilled water and ice. The operation of this system is brand-specific, so it differs for each model.



Twin Cooling Systems


Some modern refrigerators have two separate evaporator systems. It makes use of one closed system to cool the refrigerator, and another system to cool the freezer. Such a system is known as a twin cooling or dual evaporator system.


Twin cooling systems use a single compressor that connects to two separate evaporator systems. Twin cooling lets a compressor cool only the section that needs cooling. If we rarely use the freezer, then it allows us to stop cooling our freezer. This makes a refrigerator more efficient.


Cool air does not travel through the same duct to reach the two compartments. This prevents odor from transferring from one compartment to another.


When it comes to side-by-side and french door refrigerator models, they are equipped with a dispenser system. The dispenser system consists of:

  • Water dispenser, and

  • Ice maker.

Twin cooling systems make a refrigerator more efficient.



 

Electrical Systems


In this module, we will take a look at the electrical systems in a refrigerator. Skip to quiz!

Electrical


A refrigerator is an electrically powered home appliance. We generally use a single-phase power supply for domestic refrigerators.

Electrical components work together to run a refrigerator system efficiently. They’re also used to make the process of defrosting and ice-making automated.


Some of the electrical components used in a refrigerator are:

  • Electric motors,

  • Heaters, and

  • Interior lighting.

Let’s learn about each of them in detail.


Motors


Recall that an electric motor is the part of a compressor that provides rotation by consuming electricity.


Apart from the compressor, motors used in refrigerators are:

Let’s learn about each of them in detail.

Recall that we use a fan to force air over condenser coils. The motor used for running this fan is a condenser fan motor.


Recall that an evaporator fan forces air over cool evaporator coils inside a refrigerator. Much like a condenser fan motor, we use a motor to run an evaporator fan.


An auger motor spins the ice bucket auger and pushes ice through a dispenser tray. If an auger motor is burned out or defective, ice won’t move forward and fall through to the tray.


A dispenser door motor opens and closes the dispenser door to prevent cold air from escaping a freezer. If a dispenser door motor is defective, the dispenser door won’t open. As a result, a dispenser will not dispense ice.


Heaters


Refrigerators mainly use two heaters for their defrost system and ice maker. These include:

  • Defrost heater, and

  • Ice mold heater.

Let’s discuss each of them.

A defrost heater is used to melt accumulated frost off evaporator coil surfaces. Defrost heaters are commonly located beneath a refrigerator's evaporator coils.


Ice mold heaters are used to heat the ice made by an ice maker. When an ice maker freezes water in the mold, the thermostat signals a heater. A heater then activates to loosen ice cubes from their mold.


Interior Lighting


We must have noticed lights illuminating as we open a refrigerator door. This light helps to locate things inside a refrigerator when we open the door.

Refrigerator lights are controlled by a door sensor that detects the closing and opening of a door. We’ll learn about controls in a later module.


Electrical components work together to run a refrigerator system efficiently. Some of the electrical components used in refrigerators are:

  • Electric motors,

  • Heaters, and

  • Interior lighting.


 

Control Systems


In this module, we will take a look at the control systems of a refrigerator. Skip to quiz!


Controls


Along with electrical systems, we also use control systems in a refrigerator. Control systems automatically adjust the operation of a refrigerator.

In a refrigerator, control systems can be divided into:

  • Process controls,

  • Safety controls,

  • Defrost controls, and

  • Flow controls.

Let’s learn more about each type of control in detail.


Process Controls


The purpose of process control devices is to automate refrigerator operations. These include the following control devices:

  • Switches,

  • Thermostat, and

  • Sensors.

When we press a lever on our refrigerator door, it activates a small switch. This micro switch is a water dispenser switch.


Recall that a water valve is a type of solenoid valve. It remains shut and opens once it receives an electric signal.


When a water dispenser switch is pressed, it operates a water valve in the back of the appliance. This allows water to flow through the tubing into a water reservoir. That’s why when we press this lever, water is dispensed through the refrigerator door.


Ice makers have an ON/OFF switch similar to that of a light or power switch. This power switch is used to control the operation of an ice maker. If the unit is powered off, an ice maker stops making ice.


A refrigerator thermostat is essentially the primary component of a refrigerator cooling system. It tells us the inside temperature of a refrigerator. We can adjust the temperature inside a fridge using its thermostat.


Refrigerator thermostats are located inside a refrigerator. They have a knob that looks like a dial or, in more modern appliances, a digital display.

Once a user sets their desired temperature, a thermostat maintains that temperature by sensing internal fluctuations. It senses these fluctuations using a temperature sensor. Recall that a temperature sensor is placed inside or near a thermostat to detect the temperature.


When a refrigerator is adjusted to the designated temperature, a temperature sensor sends a signal to the thermostat.


The thermostat then stops the flow of electricity to the compressor, effectively stopping it from cooling the appliance.


Ice makers have a thermostat located in the ice maker mold. Once the ice maker has reached a cold enough temperature of approximately 15℉, the temperature sensor sends signal to the thermostat.


The thermostat then send electrical signals to the heating coil. This will start the heater, and ice cubes are detached from the mold.


Recall that freezer is cooler than refrigerator. This is why we use different temperature sensor to monitor temperature in each section. We use temperature sensor to monitor temperature in the: Freezer,

  • Defrost system, and

  • Refrigerator

The temperature sensor located on the evaporator coil is known as defrost sensor. This sensor does two functions:

  • Starting the defrost cycle, and

  • Stopping the defrost heater

Recall that we use defrost heater to melt accumulated ice over the evaporator coil. The defrost sensor senses evaporator temperature and sends signal to the electronic control board. If the defrost sensor senses wrong temperature, the electronic control board wont turn on the heater.


Defrost sensor shuts off the defrost heater when the heat near the evaporator has reached a temperature required to melt the ice. If the defrost sensor fails, the heating element doesn't turn on, and there will be no defrosting.


We use a temperature sensor in the freezer to monitor the freezer temperature. Similarly, the refrigerator temperature is also monitored by using a temperature sensor.


Recall that we use lights to illuminate the inside compartments of a refrigerator. These lights are turned on or off automatically when we open or close a refrigerator door. We use a door sensor to detect if an appliance door is open or closed.


A Hall effect sensor can be used to detect a door’s position. A Hall effect sensor is a type of sensor which detects the presence and magnitude of a magnetic field. This sensor is mounted to the frame of an appliance.


A permanent magnet actuator is mounted to a fridge door. A sensor and magnet actuator are positioned in such a way that the sensor is activated when the door is closed, and the light will turn off. When the door is open, the magnet on the door is outside of the sensor’s activation range, so the sensor is deactivated and the light turns on.


Ice bucket level sensors are used to detect if ice is filled to the top. They use a mechanical arm over an ice bucket, which rises and falls with the level of ice in the bucket. Once the ice reaches a certain level, a magnetic reed switch is activated.


The switch activates a level sensor, and the sensor converts the perceived data into an electric signal. When an ice bucket is filled, the sensor turns off the ice maker.


Defrost Controls

Recall that a defrost cycle occurs after every eight hours in an automatic defrost system. The frequency of defrost cycles and their duration are controlled by using a defrost timer. A defrost timer also limits the maximum amount of time that a defrost heater can be energized.


Recall that adaptive defrost control (ADC) is what makes refrigerators energy efficient. This control system is operated using a control board.


Safety Controls


Safety controls prevent a hazard from occurring. Recall that safety control circuits are always in closed condition. If any abnormality happens, these will open and turn off a refrigerator system.

Some of the safety controls present in a refrigerator are:

  • Starting relay, and

  • Overload relay.

Let’s learn more about these safety controls in detail.


The starting relay in a refrigerator is usually mounted on the compressor. They apply electricity to a secondary winding of the compressor motor to give it extra starting torque. If a refrigerator start relay is burned out, the compressor may not work, and the interior space will not refrigerate.


Overload relays are also called overload switches. In a refrigerator, overload relays are found in the compressor. They protect the motor from overheating and winding damage.


Recall that overloading is a condition when a motor draws more current than the specified range. An overload relay detects the overloading of a motor and stops the electric supply to the compressor.


Flow Controls


Flow controls regulate the flow of water needed for a refrigerator dispenser. They are installed on the backside of a refrigerator.

Some of the flow controls present in a refrigerator are:

  • Solenoid valve,

  • Water valve, and

  • Flowmeter.

Let’s learn more about these flow controls in detail.


Recall that a solenoid is a type of valve that works on control signals. A solenoid valve opens or closes whenever it receives control signals. A dispenser solenoid opens a door flap to release ice, and then closes the door flap.


A water inlet valve is located at the back of a refrigerator and connects to the water supply. The function of a water inlet valve is to supply water from the supply line to the dispenser system.


A flowmeter is located beside the water valve. A refrigerator flow meter measures the flow rate of dispensed water.


The control systems used in a refrigerator are process controls, safety controls, defrost controls, and flow controls. These control systems automatically adjust the operation of a refrigerator.


 

Complete Systems


In this module, we will take a look at the complete systems of a refrigerator. Skip to quiz!


Sequence of Operations


The complete system of a refrigerator consists of:

  • Primary and secondary components,

  • Dispenser system,

  • Defrost system,

  • Electrical system, and

  • Control system.

These systems work together to automate refrigerator operations.


The heat removal from a closed space inside a refrigerator is done by following a sequence of operations. Let’s take a look at this sequence of operations.


When we press a refrigerator switch, it turns on our refrigerator. We then set our preferred temperature on the thermostat. The thermostat senses the ambient temperature of the air in our refrigerator’s fresh-food compartment and freezer.


If the temperature inside our refrigerator is above the set point, the thermostat sends a signal to the control board. Then, the control board sends a control signal to the compressor motor starter. Recall that the starting relay controls the compressor motor in a system.


As the compressor starting relay receives the control signal, it permits electricity to flow to the compressor and fan motors. So the starting relay receives control signals from the control board and turns the compressor ON or OFF.

Starting the compressor begins the refrigeration cycle. Then refrigerant is circulated through components of the refrigeration cycle. Refrigerant absorbs heat from the food items kept inside our refrigerator.


The compressor compresses the refrigerant vapor to a high pressure and temperature. In the condenser, the high-pressure, high-temperature vapor gives up its heat to the surrounding air. The refrigerant then enters the metering device.


The refrigerant leaves the metering device as a low-pressure liquid which now enters the evaporator. When the liquid refrigerant reaches the evaporator, it absorbs heat and changes back into a gaseous state. This transformation from liquid to gas absorbs the heat in our refrigerator, and results in a cooling effect.


When the compressor starts, the control board sends a control signal to the fan relay by default. The fan relay then starts the fan motor. The fan motor is connected to the condenser, and evaporator fans start the circulation of air.


Recall that condenser fans force air over condenser coils. The evaporator fan will pull the air over the evaporator coils, which cools the air.


The cool air is circulated in the refrigerator compartment with the help of a damper. The control board sends a signal to the damper motor to open the damper. Dampers are then opened to circulate cool air in our refrigerator.


The thermostat keeps on monitoring the temperature inside the refrigerator. When the temperature reaches the thermostat setting, it sends a signal to the control board. The control board then sends a signal to the relay to turn off the compressor.


The temperature inside our refrigerator can rise again due to frequent opening and closing of the doors. Once the temperature rises above the thermostat setting, a relay receives a signal from the control board to start the compressor.


Defrost Controls


Recall that most modern refrigerators defrost automatically. Defrost controls work together to melt down the frost accumulated inside a refrigerator automatically.

When frost is formed, the temperature of an evaporator reduces considerably. A defrost sensor detects the change in temperature, and sends a signal to the thermostat. The thermostat sends a signal to the electronic control board.


The defrost timer attached to the thermostat shuts off our refrigerator. The electronic control board then starts the heater to begin the defrost cycle. As the heater gets warm, any ice or frost accumulated on the cooling coils will melt.


When the heating coil temperature increases beyond the set point, the temperature sensor sends a signal to the thermostat. The thermostat then signals the electronic control board to turn off the heater.


The defrost cycle is repeated after a definite time interval to defrost the ice. During the defrosting cycle, the ice on the evaporator coil is melted into water. The drainage system carries this water to the drainage pan.


Dispenser Controls


How to operate a dispenser to get chilled water and ice. The operation of this system is brand-specific, and it differs for each model.


When the button or lever on a water dispenser is pressed, the dispenser lever switch sends a signal to the rear coil of the water valve. This switch also sends a signal to the main control board to close the relay of the isolation valve. Recall that an isolation valve starts or stops the flow of fluid to a given location.


When both the isolation valve and water valve are open, water flows to the water reservoir inlet. When the water is chilled, the temperature sensor sends a signal to the control board.


The control board then operates the dispenser door motor. The door motor opens the dispenser door. This sends chilled water into a user's glass or container.


When we press the crushed ice or cubed ice button on our refrigerator door, we get crushed or cubed ice. The temperature of an ice maker should be below 0 ℃.


When the appropriate temperature is reached, the ice maker temperature sensor sends a signal to the thermostat. The thermostat then sends a signal to the control board. The control board sends voltage to the water inlet valve. The valve opens and allows water to flow into the ice maker's tray.


When the temperature of the ice maker lowers, the water begins to freeze. Once the ice maker has reached approximately 15℉, the temperature sensor sends a signal to the thermostat.


The thermostat then sends electrical signals to the heating coil. This will start the heater, and ice cubes are detached from their mold.


When the heater is turned on, the temperature inside the ice maker increases above the set point. The temperature sensor sends a signal to the thermostat to stop the heater.


The thermostat sends a signal to the control board to stop the heater and start the auger motor. As the auger motor rotates, the ice bucket auger turns and lifts loosened ice from the ice tray. Ice cubes are then released and dumped into a storage container in the freezer.


When a user presses the ice crusher button, the door switch sends a signal to the control board. The control board sends a signal to dispensing bucket motor. The dispensing bucket motor closes the dispensing bucket. This will not allow the cubed ice to fall into dispensing reservoir.


The cubed ice is diverted to the crushing blade system. The ice gets trapped between a rotating blade and a stationary blade to crush the ice. The crushed ice is then dispensed into a user's glass or container.


The primary and secondary components, electrical, and control systems work together to automate refrigerator operations. Defrost controls work together to melt down the frost accumulated inside a refrigerator automatically.


The isolation valve and water valve open and close to dispense water into the water reservoir. The auger motor, thermostat, temperature sensor, and control board work together to make ice cubes.



 

Question #1: What does ‘defrosting’ a refrigerator mean?

  1. Removing ice from the evaporator coil

  2. Removing ice over the compressor

  3. Removing ice over the condenser coil

  4. Removing ice over the metering device

Scroll down for the answer...















Answer: Removing ice from the evaporator coil

Defrosting is the process of removing the ice or frost from the evaporator coil or freezer.


Question #2: A semi-automatic defrost system does not require human intervention.

  1. True

  2. False

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Answer: False.

We need to push a button near the freezer to activate the defrosting function in a semi-automatic defrost system.


Question #3: What is a defrost cycle?

  1. Process of circulating cold air

  2. Time for circulating air

  3. Time duration for which defrost procedure is applied

  4. Process of making ice

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Answer: Time duration for which defrost procedure is applied

This defrost procedure is applied periodically by stopping the system. The automatic defrost takes one defrost cycle to complete.


Question #4: Which component is used to melt the ice in an automatic defrost system?

  1. Thermostat

  2. Condenser

  3. Fan

  4. Heater

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Answer: Heater

An automatic defrost system melts the ice by using a heater.


Question #5: Which system makes modern refrigerators more energy efficient?

  1. Water cooler

  2. Automatic defrost system

  3. Adaptive Defrost Control

  4. Automatic ice maker

Scroll down for the answer...














Answer: Adaptive Defrost Control

Adaptive defrost control (ADC) is what makes refrigerators energy efficient.


Question #6: How does an automatic defrost system continuously adjust the defrost intervals? (select all that apply)

  1. Monitoring the time passed since the last defrost cycle

  2. Monitoring the air temperature in a room

  3. Monitoring the temperature of the freezer

  4. Monitoring the number of door openings

Scroll down for the answer...









Answer: Monitoring the time passed since the last defrost cycle

Monitoring the number of door openings

Adaptive defrost control (ADC) will continually adjust the defrost intervals based on the following:

  • Number of door openings,

  • Compressor run time, and

  • The time passed after the last defrost cycle.


Question #7: What is the function of a drain pan?

  1. To make ice

  2. To dispense water

  3. To collect water from a defrost system

  4. To filter water

Scroll down for the answer...











Answer: To collect water from a defrost system

A drain pan is a water tray that collects and stores water.


Question #8: What features are offered by a refrigerator's dispenser? (select all that apply)

  1. Chilled water

  2. Crushed ice

  3. Ice-cream

  4. Cubed ice

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Answer: Chilled water, Crushed ice and Cubed ice

The commonly offered features of refrigerator dispensers are:

  • Chilled water,

  • Crushed ice, and

  • Cubed ice


Question #9: What is the water source for a dispenser system in a refrigerator?

  1. Water is not required in a dispenser

  2. Water supply line connected to the refrigerator

  3. Water made by melting ice

  4. Rain water

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Answer: Water supply line connected to the refrigerator

The water for the dispenser system in a refrigerator is supplied by one of the following means:

  • Water supply line connected to the refrigerator, or

  • Manually filling the dispenser water tank.


Question #10: Which of the following is a component used inside a refrigerator ice maker? (select all that apply)

  1. Ice bucket auger

  2. Compressor

  3. Crusher blade

  4. Condenser

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Answer: Ice bucket auger and Crusher blade

The mechanical components present inside an ice maker unit are:

  • Ice tray,

  • Ice bucket auger, and

  • Ice crusher blade.


Question #11: What is the purpose of the heating coil inside an ice maker?

  1. Loosen ice from the tray

  2. Melt ice in its tray

  3. Defrost ice over evaporator coil

  4. Make chilled water

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Answer: Loosen ice from the tray

After the ice cubes have been created, a heating coil is activated to loosen them from their trays.


Question #12: A twin cooling system use two separate compressors to make the refrigerator more efficient.

  1. False

  2. True

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Answer: False.

Twin cooling systems use a single compressor that connects to two separate evaporator systems.This makes the refrigerator more efficient.


Question #13: Which of the following electrical components is not used in a domestic refrigerator?

  1. Electric motors

  2. Heaters

  3. Interior lighting

  4. Economizer

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Answer: Economizer

The electrical components used in a refrigerator are:

  • Electric motors,

  • Heaters, and

  • Interior lighting


Question #14: What is the purpose of a condenser fan?

  1. Make ice

  2. Force air over the condenser

  3. Defrost ice over evaporator coil

  4. Reduce humidity

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Answer: Force air over the condenser

The condenser fan forces air over the condenser coils inside a refrigerator.


Question #15: Which motor do we use inside an ice maker?

  1. Condenser fan motor

  2. Expansion valve motor

  3. Auger motor

  4. Evaporator fan motor

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Answer: Auger motor

We use an auger motor inside an ice maker. An auger motor spins the ice bucket auger and pushes ice through a dispenser tray.


Question #16: What is the function of a defrost heater?

  1. Make ice

  2. Melt accumulated frost off evaporator coils

  3. Heat the water in a refrigerator

  4. Cool the water in a refrigerator

Scroll down for the answer...









Answer: Melt accumulated frost off evaporator coils

We use an auger motor inside an ice maker. An auger motor spins the ice bucket auger and pushes ice through a dispenser tray.


Question #17: What is the function of an ice mold heater?

  1. Crush the ice in the mold

  2. Melt accumulated ice off the evaporator

  3. loosen the ice cubes from their mold

  4. Dispense hot water


Scroll down for the answer...











Answer: loosen the ice cubes from their mold

Ice mold heater is used to loosen the ice cubes from their mold.


Question #18: Refrigerator lights help kill bacteria on our food.

  1. True

  2. False

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Answer: False.

Refrigerator light helps to locate the things inside a refrigerator when we open the door.


Question #19: An ice maker switch operates a water valve present at the back of the appliance.

  1. True

  2. False

Scroll down for the answer...











Answer: False.

An ice maker has an ON/OFF switch similar to that of a light or power switch. This power switch is used to control the operation of an ice maker.


Question #20: What is the function of a thermostat inside a refrigerator?

  1. Reduce humidity

  2. Adjust the temperature

  3. Dispense hot water

  4. Crush the ice in the mold

Scroll down for the answer...









Answer: Adjust the temperature

We can adjust the temperature inside a fridge using a thermostat.


Question #21: Where do we use temperature sensors to monitor refrigerator temperature fluctuations? (Select all that apply)

  1. Freezer

  2. Condenser fan

  3. Refrigerator

  4. Defrost system

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Answer: Freezer, Refrigerator and Defrost system

We use temperature sensor to monitor temperature in the:

  • Freezer,

  • Defrost system, and

  • Refrigerator


Question #22: What is the role of ice bucket level sensor in a refrigerator?

  1. Detect both ice bucket temperature and pressure

  2. Detect ice bucket temperature

  3. Detect ice bucket pressure

  4. Detect ice bucket level

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Answer: Detect ice bucket level

Ice bucket level sensor is used to detect if ice is filled to the top.


Question #23: What does a defrost timer do? (select all that apply)

  1. Control frequency of defrost cycle

  2. Set water filling time in the ice maker

  3. Control duration of defrost cycle

  4. Set time for ice making

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Answer: Control frequency of defrost cycle and Control duration of defrost cycle

The frequency of the defrost cycles and their duration are controlled by using a defrost timer.


Question #24: Which of the following safety devices are used inside a refrigerator? (select all that apply)

  1. Starting relay

  2. Motor winding thermostats

  3. Overload relay

  4. Compressor

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Answer: Starting relay and Overload relay

Safety controls present in a refrigerator are:

  • Starting relay, and

  • Overload relay


Question #25: Which of the following flow controls used inside a refrigerator? (select all that apply)

  1. Back pressure regulating valve

  2. Solenoid valve

  3. Hot gas bypass valve

  4. Water valve


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Answer: Solenoid valve and Water valve

Flow controls present in a refrigerator are:

  • Solenoid valve,

  • Water valve, and

  • Flowmeter

Question #26: Which system is present inside a refrigerator? (select all that apply)

  1. Electrical and control system

  2. Dispenser system

  3. Defrost system

  4. Comfort air cooling

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Answer: Electrical and control system, Dispenser system and Defrost system

The complete system of a refrigerator include:

  • Primary and secondary components

  • Dispenser system,

  • Defrost system,

  • Electrical system, and

  • Control system


Question #27: What is the correct operating sequence of a refrigerator?

  1. Refrigeration cycle starts after the water dispenser unit

  2. Starting the compressor starts the refrigeration cycle.

  3. Refrigeration cycle starts before start of compressor

  4. Refrigeration cycle commences before the refrigerator is turned on

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Answer: Starting the compressor starts the refrigeration cycle.

The contactor receives control signals from the thermostat and turns the compressor ON or OFF. Starting the compressor starts the refrigeration cycle.


Question #28: What controls the operation of a refrigerator compressor?

  1. Thermostat and relay

  2. Door sensor

  3. Condenser fan motor

  4. Evaporator fan motor

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Answer: Thermostat and relay

The thermostat and relay control the operation of the refrigerator compressor. When the temperature reaches the thermostat setting, it sends a signal to the relay to turn off the compressor.


Question #29: Which component is used to defrost the ice in a freezer?

  1. Thermostat and relay

  2. Defrost heater

  3. Vacuum cleaner

  4. Evaporator fan

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Answer: Defrost heater

Defrost heater is used to defrost the ice in a freezer. As the heater gets hot, any ice or frost accumulated on the cooling coils will melt.


Question #30: What is the correct operation of a refrigerator’s water dispenser?

  1. Thermostat and relay open to dispense water

  2. Water valve opens to dispense water through dispenser

  3. Isolation valve and water valve is open to fill the water reservoir

  4. Ice level is checked before dispensing water

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Answer: Isolation valve and water valve is open to fill the water reservoir

When both the isolation valve and water valve are open, water flows to the water reservoir inlet.


Question #31: Which of the following component work together to make ice cubes in a refrigerator? (select all that apply)

  1. Thermostat and temperature sensor

  2. Door sensor

  3. Auger motor and control board

  4. Condenser fan

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Answer: Thermostat and temperature sensor and Auger motor and control board

The Auger motor, thermostat, temperature sensor, and control board work together to make ice cubes.

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