Sharp REFRIGERATOR-FREEZER SJ-58LM-C2W/C2G/C2B_SJ-63LM-C2W/C2G/C2B_
SJ-68LM-C2W/C2G/C2B/C2S _Working principle_Wiring diagram_Fault symptoms
FROST-FREE SYSTEM
The main difference between frost-free refrigerators and those that are not frost-free is the location of the evaporator. Previously we have seen that the evaporator is located inside the refrigerator and it is responsible for the removal of the inside heat With frost-free refrigerators the evaporator is located outside the food storage compartments at the rear.
Warm air is drawn over the evaporator. The evaporator will remove the heat from this airflow and any moisture leaving a cold dry flow of air, which is ducted, around the food compartments
The main difference between frost-free refrigerators and those that are not frost-free is the location of the evaporator. Previously we have seen that the evaporator is located inside the refrigerator and it is responsible for the removal of the inside heat With frost-free refrigerators the evaporator is located outside the food storage compartments at the rear.
Warm air is drawn over the evaporator. The evaporator will remove the heat from this airflow and any moisture leaving a cold dry flow of air, which is ducted, around the food compartments
The above diagram shows the construction of the SJ-51J, it can be
seen that there is a propeller fan situated above the evaporator. As this fan
rotates air will be drawn across the evaporator and forced into the fridge and
freezer compartments. As this air flow’s around these compartments the air temperature
will rise collecting any heat it finds. This warmed air is returned to the
evaporator, where the air is once again cooled, the air is then re-circulated. Although this system is referred to as
frost-free all it means is that the compartments do not become frosted. The
evaporator will still develop ice, which has to be defrosted. This can be
carried out automatically.
To regulate the temperature in the freezer and refrigerator compartments a temperature control is add to each compartment.
To regulate the temperature in the freezer and refrigerator compartments a temperature control is add to each compartment.
Wiring diagram
AUTO DEFROST
The defrosting timer counts the operation time of the compressor,
When the count time reaches between 8 to 11 hours depending on model and
frequency of the supply (UK model SJ-48J operating on 230v @ 50Hz the time counted
is 10hours, 46 minutes) the timer will switch to the defrost cycle.
DEFROST CYCLE
When the timer changes to ‘defrost cycle’, the compressor and timer motors supply is switched to the defrost heater and defrost thermostat (defrost initiated) stopping the timer and compressor. Once the ice in the evaporator has melted. Defrost thermostat (SJ-48J activates at 10ºC) turns off (open circuit) ending the
defrost cycle. The time taken for the defrost cycle to complete will vary depending on the amount of ice in the vicinity of the defrost thermostat typically the defrost cycle will take between 20 to 30 minutes.
When the timer changes to ‘defrost cycle’, the compressor and timer motors supply is switched to the defrost heater and defrost thermostat (defrost initiated) stopping the timer and compressor. Once the ice in the evaporator has melted. Defrost thermostat (SJ-48J activates at 10ºC) turns off (open circuit) ending the
defrost cycle. The time taken for the defrost cycle to complete will vary depending on the amount of ice in the vicinity of the defrost thermostat typically the defrost cycle will take between 20 to 30 minutes.
WATER DISCHARGE
When the defrost thermostat switches to off (open circuit) current will flow from the timer switch via the defrost heaters through the timer and compressor motors During this time the water from the melted ice will flow to the evaporator pan located at the bottom. After 2 minutes, 24 seconds (50Hz models) the timer switch will activate allowing current to flow from the timer switch to the compressor (cooling starts). The heat radiating from the sub-condenser evaporates the water in the evaporator pan.
When the defrost thermostat switches to off (open circuit) current will flow from the timer switch via the defrost heaters through the timer and compressor motors During this time the water from the melted ice will flow to the evaporator pan located at the bottom. After 2 minutes, 24 seconds (50Hz models) the timer switch will activate allowing current to flow from the timer switch to the compressor (cooling starts). The heat radiating from the sub-condenser evaporates the water in the evaporator pan.
COOLING OPERATION
The timer motor will stop operating when the defrost-thermostat turns on (short circuit), this occurs when the temperature falls (SJ-48J = 1ºC). This takes approximately 5 minutes. Once the defrost-thermostat contacts have closed the timer will start to count the compressor operation time. After 8 hours, 46 minutes the defrost-cycle will start again.
The timer motor will stop operating when the defrost-thermostat turns on (short circuit), this occurs when the temperature falls (SJ-48J = 1ºC). This takes approximately 5 minutes. Once the defrost-thermostat contacts have closed the timer will start to count the compressor operation time. After 8 hours, 46 minutes the defrost-cycle will start again.
CHECKING OF DEFROST SYSTEM
1. Operate the refrigerator for 20 to 30 minutes.
2. Turn refrigerator off.
3. Wait 5 minutes then restart the compressor (immediate re-start cause un-smooth operation.
4. Turn the timer shaft clockwise with a screwdriver until the compressor stops (The timer switch contacts can be heard operating).
5. Defrost Cycle will now be activated, wait 5 minutes.
6. Turn the timer shaft clockwise with a screwdriver until the compressor starts.
7. Ensure cooling operation is started again
1. Operate the refrigerator for 20 to 30 minutes.
2. Turn refrigerator off.
3. Wait 5 minutes then restart the compressor (immediate re-start cause un-smooth operation.
4. Turn the timer shaft clockwise with a screwdriver until the compressor stops (The timer switch contacts can be heard operating).
5. Defrost Cycle will now be activated, wait 5 minutes.
6. Turn the timer shaft clockwise with a screwdriver until the compressor starts.
7. Ensure cooling operation is started again
FAULT SYMPTOMS
DEFROST HEATER OR THERMAL FUSE OPEN CIRCUIT
1. Defrost cycle is extremely prolonged
2. The, the freezer temperature rises (food will start to defrost), due to the compressor not functioning.
3. Timer motor will only operate if manually set to the cooling mode.
4. Defrost Thermostat will be always on.
DEFROST THERMOSTAT OPEN CIRCUIT.
1. Timer motor will not run
2. Defrosting will not take place
3. Evaporator becomes frozen
4. Timer motor will only operate if set manually to the Defrost cycle, but stops when switched to cooling cycle.
DEFROST HEATER OR THERMAL FUSE OPEN CIRCUIT
1. Defrost cycle is extremely prolonged
2. The, the freezer temperature rises (food will start to defrost), due to the compressor not functioning.
3. Timer motor will only operate if manually set to the cooling mode.
4. Defrost Thermostat will be always on.
DEFROST THERMOSTAT OPEN CIRCUIT.
1. Timer motor will not run
2. Defrosting will not take place
3. Evaporator becomes frozen
4. Timer motor will only operate if set manually to the Defrost cycle, but stops when switched to cooling cycle.
[Defrost thermostat contains a thermal-fuse, this is safety device
and should never be short-circuited under any circumstances.]
DEW PREVENTION
The hot pipe (D.P-Condenser) is arranged under the cabinet cover and under the ‘C’ Partition Plate (Chilled Case) in a manor, which will prevent any dew occurring.
The hot pipe (D.P-Condenser) is arranged under the cabinet cover and under the ‘C’ Partition Plate (Chilled Case) in a manor, which will prevent any dew occurring.
As the name suggest the hot pipe will be hot while the compressor
is running. This should be explained to the end user that it is normal if there
are any queries about areas of the refrigerator being warm or hot.
Peltier effect: Refrigeration using
electronic means When two dissimilar metals are joined to make a closed
circuit, and one is heated and the other cooled, an electric current flows
through the junction of the two materials. This phenomenon, known as the
Seebeck effect, is widely used in thermocouple thermometers for the indirect
measurement of temperature. Conversely,
when an electric current is passed through the junction one of the materials
cools and the other heats (Peltier effect). Electronic refrigeration is achieved
by making use of the cooled zone Since materials possessing good electrical
conductivity are normally also good conductors of heat, the temperature of the
cooled junction may be increased by heat conducted from the other junction,
which means the selection of appropriate junction materials is of great
importance. Although suitable semiconductor materials have been developed and
are now available, this refrigeration method is little used in practice because
the performance coefficient is very low.
VAPOUR CONDENSATION
When the refrigerant is compressed its temperature will rise resulting in the gas being vaporized. A vapor has the characteristic of increasing in temperature as the pressure is increased. This means that the condensation temperature will also rise. Conversely, if the pressure is lowered, than the condensation temperature will fall. Heat is absorbed from the area surrounding the evaporator (located inside the refrigerator) and transported away by the refrigerant gas. This gas and can be easily made to release heat by increasing the pressure such that the condensation temperature becomes higher than the ambient
temperature. When the refrigerant gas in the condenser condenses and returns to a liquid state, the latent heat of condensation is released and is removed by air or water. Thus, the temperature of the refrigerant itself does not change very much The condenser piping is surrounded by metal fins, this ensures an efficient dispersal of heat from the condenser.
When the refrigerant is compressed its temperature will rise resulting in the gas being vaporized. A vapor has the characteristic of increasing in temperature as the pressure is increased. This means that the condensation temperature will also rise. Conversely, if the pressure is lowered, than the condensation temperature will fall. Heat is absorbed from the area surrounding the evaporator (located inside the refrigerator) and transported away by the refrigerant gas. This gas and can be easily made to release heat by increasing the pressure such that the condensation temperature becomes higher than the ambient
temperature. When the refrigerant gas in the condenser condenses and returns to a liquid state, the latent heat of condensation is released and is removed by air or water. Thus, the temperature of the refrigerant itself does not change very much The condenser piping is surrounded by metal fins, this ensures an efficient dispersal of heat from the condenser.
REFRIGERATION METHODS
Fusion: Refrigeration-using ice
For the solid we call ice to melt and become a liquid 333 5 kJ (79 68 kcal) of heat is required per 1 kg of ice. The air in a hot room will become cooler if a block of ice placed in it. This is because as the melts it is using the heat surroundings it. The melting point of ice is 0ºC only when the ice is in contact with the pure water; if salt is added to the water, the melting is lowered. This is called a cryogen or freezing mixture. If 330g of salt is added to 1 kg of ice or snow, a temperature as low as -21ºC can be obtained
Sublimation: Refrigeration using dry ice Before potable refrigeration, ice cream salesman would prevent their stocks of ice cream from melting, by placing a white block that emitted smoke next to the ice cream. This was a piece of dry ice (solidified carbon dioxide), and the white smoke-like substance is really moisture in the air freezing. Unlike ice, dry ice changes directly from a solid to a gas, so the container always remains dry. It is used for keeping and transporting foods such as butter, cheese, ice cream, fish, etc. Dry ice sublimates at -78ºC and becomes carbon dioxide (CO 2). The heat of sublimation is 573 5 kJ/kg (137 kcal/kg), compared with 333 5 kJ (79 68 kcal) for ice fusion. Hence, the refrigeration ability of dry ice is far greater than that of ice, and a smaller amount is needed to achieve the same refrigerating capability. Dry ice was also used for producing smoke effects during theatrical productions.
Fusion: Refrigeration-using ice
For the solid we call ice to melt and become a liquid 333 5 kJ (79 68 kcal) of heat is required per 1 kg of ice. The air in a hot room will become cooler if a block of ice placed in it. This is because as the melts it is using the heat surroundings it. The melting point of ice is 0ºC only when the ice is in contact with the pure water; if salt is added to the water, the melting is lowered. This is called a cryogen or freezing mixture. If 330g of salt is added to 1 kg of ice or snow, a temperature as low as -21ºC can be obtained
Sublimation: Refrigeration using dry ice Before potable refrigeration, ice cream salesman would prevent their stocks of ice cream from melting, by placing a white block that emitted smoke next to the ice cream. This was a piece of dry ice (solidified carbon dioxide), and the white smoke-like substance is really moisture in the air freezing. Unlike ice, dry ice changes directly from a solid to a gas, so the container always remains dry. It is used for keeping and transporting foods such as butter, cheese, ice cream, fish, etc. Dry ice sublimates at -78ºC and becomes carbon dioxide (CO 2). The heat of sublimation is 573 5 kJ/kg (137 kcal/kg), compared with 333 5 kJ (79 68 kcal) for ice fusion. Hence, the refrigeration ability of dry ice is far greater than that of ice, and a smaller amount is needed to achieve the same refrigerating capability. Dry ice was also used for producing smoke effects during theatrical productions.
Vaporization: Refrigeration using
halogenated hydrocarbons (Freon) or ammonia when we are given an injection, our
skin is sterilized by rubbing it with a piece
of cotton wool soaked in alcohol. The alcohol on the skin surface is heated by body and released into the air as alcohol vapor. Thus, the heat needed to make the alcohol vaporize is taken away from the skin, which, as a result, feels cool.
In a refrigerator, a large quantity of a halogenated-hydrocarbon liquid, which has an extremely strong cooling effect, is vaporized inside an evaporator, which consequently becomes cold That is to say, when the easily vaporized halogenated-hydrocarbon liquid vaporizes, the heat needed for vaporization is extracted from the food to be refrigerated. This is how the refrigeration of food is achieved.
of cotton wool soaked in alcohol. The alcohol on the skin surface is heated by body and released into the air as alcohol vapor. Thus, the heat needed to make the alcohol vaporize is taken away from the skin, which, as a result, feels cool.
In a refrigerator, a large quantity of a halogenated-hydrocarbon liquid, which has an extremely strong cooling effect, is vaporized inside an evaporator, which consequently becomes cold That is to say, when the easily vaporized halogenated-hydrocarbon liquid vaporizes, the heat needed for vaporization is extracted from the food to be refrigerated. This is how the refrigeration of food is achieved.
Electric Accessories Layout
INSPECTION OF INITIAL STARTING
(1) Inspection of cooling unit
1. Set the temperature control knob to "MAX" and check that the compressor starts to operate.
2. Depress the door switch to run the fan and check that cool air is blown out of the cold air outlet of the freezer and the refrigerator.
3. When the compressor does not work, check that the timer is not set to "defrost" position.
4 It takes about an hour and a half or two hours to put food in the refrigerator after starting operation.
NOTE: After return the temperature control knob to "MED" position. When the refrigerator is operated initially after installed, the compressor may vibrate excessively for 1 to 2 min. However, vibration becomes normal if it is continuously operated.
(2) Inspection of defrost device
Operate the refrigerator for 20 to 30 min. and then check the defrost device in the following procedures :
Allow 5 min. to restart the compressor since immediate starting after stopping will cause unsmooth operation.
1. Turn the timer shaft clockwise with a screw driver. At this time, make certain the timer clinks and the compressor stops.
2. After more than 5 min., turn the shaft further to operate. Make certain cooling operation is started again.
(1) Inspection of cooling unit
1. Set the temperature control knob to "MAX" and check that the compressor starts to operate.
2. Depress the door switch to run the fan and check that cool air is blown out of the cold air outlet of the freezer and the refrigerator.
3. When the compressor does not work, check that the timer is not set to "defrost" position.
4 It takes about an hour and a half or two hours to put food in the refrigerator after starting operation.
NOTE: After return the temperature control knob to "MED" position. When the refrigerator is operated initially after installed, the compressor may vibrate excessively for 1 to 2 min. However, vibration becomes normal if it is continuously operated.
(2) Inspection of defrost device
Operate the refrigerator for 20 to 30 min. and then check the defrost device in the following procedures :
Allow 5 min. to restart the compressor since immediate starting after stopping will cause unsmooth operation.
1. Turn the timer shaft clockwise with a screw driver. At this time, make certain the timer clinks and the compressor stops.
2. After more than 5 min., turn the shaft further to operate. Make certain cooling operation is started again.
SYMPTOM After the freezer door is opened and
closed, an abnormal sound is heard from inside the refrigerator.
CAUSE When the freezer door is
opened, warm air gets into the freezer compartment. After the freezer door is
closed, warm air circulates into evaporator and cools. When the warm air cools
it contracts, thus decreasing the pressure inside the refrigerator. As the door
gasket of the refrigerator is sealed tightly, the outside air presses the
refrigerator cabinet inwards, thus deforming the cabinet slightly as shown in
figure 1. This forces the food liner to move a little inside. As a result of
this movement, the refrigerator shelf slides on the food liner. See figure 2.
In a few cases, the bottom of the center partition slides on the food liner.
See figure 2. When the friction between the food liner and the shelf is great,
a loud noise is heard. This friction depends on the food liner surface and the
shelf surface condition and also depends on the weight of stocked foods. If
either the friction is small or the shelf/center partition slides slowly, the
sound is not so loud. When the friction is great, the shelf is difficult to
move, therefore increasing the stress between food liner and shelf so that
finally the shelf moves making a loud noise.
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