Digital Countertop Service Manual 7
SEQUENCE OF OPERATION
Power Supply
Electrical Power is supplied to the oven by a three conductor cord set.
Black conductor is HOT.
White conductor is HOT.
Green conductor is ground.
Line voltage is supplied through the fuses(F1, F2)and line one(L1) through the
manual resettable control box high limit(T1) to the ON/OFF switch, the Cooling
Fan Thermostat(T2), the Cool Down Timer(TD), and to the Main Fan Relay(R2).
Control Box Auto Cool Down
The cooling fan thermostat is connected to the axial fan that cools the control
box. Line two (L2) connects to the other side of the Control Box Cooling Fan
motor bypassing the ON/OFF switch. The thermostat closes at 120°F cycling the
fan keeping the control box below 120°F
Main Fan Circuit
Upon activating the ON/OFF switch, power is supplied to the Cool Down Timer
(TD) through the timer (TD) to the Main Fan Relay (R2) through the relay (R2) to
power the Main Fan (M1).
Heating Circuit
When the heating contactor then closes, supplying line voltage to the SSR for
the heater. Line voltage is then supplied to the element through the SSR as
needed to maintain set point temperature.
Oven Control
Upon closing the ON/OFF switch, the transformer is supplied line voltage and
then supplies 24 VAC to the control board and controls the conveyor motor. The
control reads the thermocouple and cycles the SSR to the heater to maintain set
point temperature. The control board also reads the input from the key pad to
make adjustments for cook time and temperature.
Conveyor Drive
The control board transformer’s (XR) secondary supplies 24 VAC to the control
board (CNTR). The conveyor control converts AC to DC and DC power is
supplied to the conveyor motor (M3). 2-29 VDC is supplied to the motor (M3)
through 4 wires (2 sets A+ A- & B+ B-).
