Electrolux MCC4060E Service Manual page 17

Door
Oven Cavity
Roller Stay
Figure D-2. Convection Cooking System
FIRE SENSING FEATURE
The oven will stop its operation when there is a fire in the
oven cavity in microwave cooking condition.
LSI measures the voltage across the temperature
measurement circuit intermittently within 32-seconds time
base since the oven is started in microwave cooking
condition. The oven will stop its operation when the
difference of the voltage is more than 0.39 volts in
microwave cooking condition.
1. Within a 32-seconds base, the thermistor is energized
for 2 seconds. At that time, the voltage across the
temperature measurement circuit is measured.
2. The oven carries out the procedure above again. If the
second voltage is 0.39V higher than first voltage, LSI
judges it is a fire in the oven cavity and stop the oven.
3. When LSI judges it is a fire in the oven cavity, LSI will
switch off the relays to high voltage transformer and
fan motor and LSI stops counting down.
OPEN JUDGE BY THERMISTOR
1. If the temperature of the thermistor does not rise to
more than 40°C after 4 minutes and 15 seconds from
when the oven is started in convection, grill or dual
cooking mode, the oven is turned off.
2. When the thermistor or the wire harness to the
thermistor is opened, the oven is turned off after 4
minutes and 15 seconds because this condition is
same as above.
THERMISTOR
SENSING
VOLTAGE
SOI 12.06 FV
FUNCTION OF IMPORTANT COMPONENTS
Grill Heating
Convection
Elements
Passage
Convection
Heating Element
Cooling
Fan
Convection
Turntable
Motor
Convection
Fan
Turntable Motor
DAMPER OPEN-CLOSE MECHANISM
Damper position is set automatically by damper motor
DM, damper switch and motor cam.
These components are operated by a signal that
judges if microwave cooking or convection cooking
operation is selected by the CPU unit.
Microwave Cooking:
Damper is in the open position, because a portion of
cooling air is channelled through the cavity to remove
steam and vapours given off from the heating foods.
It is then exhausted at the top of the oven cavity into a
condensation compartment.
Convection Cooking:
Damper is in the closed position, so that no hot air will
be allowed to leak out the oven cavity.
Damper Operation
1. When power supply cord is plugged in or when
the control unit resumes after energy save mode
finishes:
1-1. When power supply cord is plugged in, a signal
is sensed in the control unit, and operates shut-
off relay (RY8).
1-2. Contacts of shut-off relay (RY8) close, the
damper motor DM is energized, opening the
damper door.
1-3. When the damper is moved to the open position
by the damper cam, damper switch SW4 is
closed (ON position).
1-4. The signal of damper switch SW4 is re-sensed
in the control unit and shut-off relay (RY8) is
turned off.
1-5. The rated voltage to the damper motor DM is
stopped and the motor turns off.
2. When oven is microwave cooking:
Damper is in the open position
3. When oven is convection cooking:
3-1 Damper motor DM is energized right after the
oven is started.
3-2. When damper is in the closed position (damper
switch SW4 is OFF), its signal is sensed by the
control unit, and shut-off relay (RY8) is de-
energized.
3-3. The damper is held in the closed position during
the convection cooking operation.
3-4. At the end of the convection cooking, when the
fan motor FM stops, shut-off relay (RY8) is
energized, and the damper is returned to the
open position.
NOTE: If the damper door is not in the proper
position, closed during convection, grill or
dual, or open during microwave, the control
unit will stop oven operation after 1 minute.
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