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CONVECTION HEATER
The convection heater is located at the rear of the oven
cavity. It is intended to heat air driven by the convection
fan. The heated air is kept in the oven and force-circulated
and reheated by the convection heater.
THERMAL CUT-OUT 150˚C (OVEN)
The thermal cut-out protects the convection motor against
overheating. If its temperature rises above 150˚C because
the convection fan motor is interrupted, the ventilation
openings are obstructed or the other abnormal matter
occurs, the thermal cut-out opens and switch off the oven.
When the thermal cut-out cools itself down to 130˚C, the
contacts of the thermal cut-out will close again.
THERMAL CUT-OUT 95˚C (FAN MOTOR)
The thermal cut-out protect the fan motor against over-
heating. If its temperature goes up higher than 95˚C
because the fan motor is locked or the ventilation operat-
ing are blocked, the contacts of the thermal cut-out will
open and switch off the oven. When the thermal cut-out
cools itself down to 75˚C, the contacts of the thermal cut-
out will close again.
TEMPERATURE FUSE 150˚C (MG)
This fuse protects the magnetron against overheating. If
the temperature goes up higher than 150˚C because the
fan motor is interrupted, the air inlet duct is blocked or the
ventilation operating are obstructed, the fuse blows and
cuts off the power supplying to the power transformer. The
defective fuse must be replaced with new rated one.
THERMAL CUT-OUT 145˚C (MG)
This thermal cut-out protects the magnetron against over-
heating. If the temperature goes up higher than 145˚C
because the fan motor is interrupted, the air inlet duct is
blocked or the ventilation operating are obstructed, the
fuse blows and cuts off the power supplying to the power
transformer. The defective thermal cut-out must be re-
placed with new rated one.
CONVECTION COOKING SYSTEM
This oven is designed with a hot air heating system where
food is not directly heated by the convection heater, but is
heated by forced circulation of the hot air produced by the
convection heater.
The air heated by the convection heater is circulated
through the convection passage provided on the outer
casing of the oven cavity by means of the convection fan
which is driven by the convection motor. It then enters the
inside of the oven through the vent holes provided on the
left side of the oven. Next, the hot air heats the food on the
turntable and leaves the oven cavity through the vent in the
oven cavity left side wall.
Without leaving the oven, this hot air is reheated by the
convection heater, passes through the convection pas-
sage and enters the inside of the oven cavity again, in a
continuing cycle.
In this way, the hot air circulates inside the oven cavity to
raise its temperature and, at the same time, comes into
contact with the food being cooked.
When the temperature inside the oven cavity reaches the
selected temperature, the convection heater is de-ener-
gized. When the temperature inside the oven cavity drops
below the selected temperature, the convection heater is
energized again. In this way, the inside of the oven cavity
is maintained at approximately the selected temperature.
When the convection time reaches 0, the convection
heater is deenergzed and the convection fan stops oper-
ating and the oven shuts off.
Upon completion of the cooking time, the audible signal
will sound, and oven lamp, turntable motor, cooling fan
motor and convection motor are de-energized. At the end
of the convection cycle, if the cavity air temperature is
above 118˚C, the circuit to RY6 will be maintained (by the
thermistor circuit) to continue operation of the cooling fan
motor until the temperature drops below 118˚C, at which
time the relay will be de-energized, turning off the fan
motor. Relay RY5 will however, open as soon as the
convection cycle has ended, turning off the convection fan
motor. This will now cool and allow the damper door to
open.
DAMPER OPEN-CLOSE MECHANISM
Usually, the damper is in the open position except during
convection cooking.
Damper position is set automatically by damper motor,
damper switch, motor cam and damper shaft.
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:
1-1. When power supply cord is plugged in, a signal is
sensed in the control unit, and operates shut-off relay
(RY4).
1-2. Contacts of shut-off relay (RY4) close, the damper
motor is energized, opening the damper door.
1-3. When the damper is moved to the open position by
the damper cam, damper switch is closed (ON
position).
1-4. The signal of damper switch is re-sensed in the
control unit and shut-off relay (RY4) is turned off.
1-5. The 240 volts A.C. to the damper motor 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 is energized by touching the convection,
temperature and START pads.
3-2. When damper is in the closed position (damper
switch is OFF), its signal is sensed by the control unit,
and shut-off relay (RY4) is de-energized.
3-3. The damper is held in the closed position during the
convection cooking operation
9
R-995J
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