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34 OVEN SYSTEMS
High Limit Thermostat
The high limit thermostat is a 250 VAC, 3-pole,
manual-reset thermostat with a trip point of 572
º
F
(300
º
C). The thermostat interrupts power to the
main convection heater in the event of an abnormal
condition.
Reset the high-limit thermostat by pressing the
reset button (Figure 31).
Keypad
The keypad is a 7 x 10 matrix membrane switch.
For details on key functions, see page 9.
Magnetron Cooling Fans
The magnetron cooling fans supply air to the
magnetrons, and are actuated by the K7 relay. They
operate at:
- 208/240 VAC (60 Hz installations with voltage
sensing)
- 220 VAC (60 Hz installations with no voltage
sensing)
- 230 VAC (50 Hz installations)
- 200 VAC (Japan installations)
Magnetron Thermostats
The magnetron thermostats are “open-on rise.”
They are designed to open at 212
º
F (100
º
C),
which triggers an F5 fault.
NOTE: The magnetron thermostats are wired in
series. If one opens, the control will switch off both
microwave systems until the open thermostat
closes. The thermostats are self-resetting.
Power Supply
The power supply outputs 24 VDC at 40 watts to
the control board and relays.
Relay - K1 Filament
The K1 relay is a 240 VAC, 30 amp, double-pole,
double-throw, 24 VDC relay coil. It switches power
to the magnetron filament transformers.
Relay - K2 Anode
The K2 relay is a 240 VAC, 30 amp, double-pole,
double-throw, 24 VDC relay coil. It switches power
to the magnetron high-voltage transformers.
Relay - K3 Monitor
The K3 relay is a 240 VAC, 30 amp, double-pole,
double-throw, 24 VDC relay coil. It shorts L1 and
L2 if the monitor switch opens before the primary
or secondary switches.
Relay - K6 Voltage
The K6 relay is a 240 VAC, 30 amp, three-pole,
double-throw, 24 VDC relay coil. Applicable in
North America only, it switches between 208 and
240 VAC on the high-voltage transformer and
filament transformer taps (depending on incoming
voltage).
Figure 31: High-Limit Reset Button
Reset
Button