Service manual

FULL SIZE GAS CONVECTION OVENS - ELECTRICAL OPERATION
F24682 (Rev. B, October 2007)Page 31 of 68
Computer Control
(VC4GC/6GC) ................. Monitors temperature sensor and regulates the oven cavity temperature by
controlling the heat relay (R1) through the blower motor centrifugal switch
contacts. Also, counts the ROAST time (normal cooking) of the product and
signals the electronic alarm at the end of the cycle. If ROAST & HOLD
mode is selected, when the ROAST (then hold) time expires, the oven
heating stops and the oven enters HOLD mode. Once the oven cavity
temperature drops to 150°F, the heat comes back on and the oven cycles
at this temperature to hold the cooked product. Roast & Hold is standard on
computer models.
SSR1 & SSR2 (VC4GC/6GC) ..... When SSR1 is energized by computer control, connects power to blower
motor for Hi fan speed operation in normal ROAST mode. In ROAST &
HOLD Mode only, SSR1 is de-energized and SSR2 is energized by
computer control and connects power to blower motor for Low fan speed
operation.
Ignition Control Module ......... Controls the gas ignition cycle - Energizes the 2
nd
valve (main) on the dual
solenoid gas valve, generates spark for burner ignition, monitors the
presence of a flame and controls the No Ignition light. The ignition times
are: 4 second self diagnostic test (initial power ON); 7 second ignition trial;
3 ignition trials with a 15 second purge between each trial.
Igniter/Flame Sense ............ Ignites the gas and senses the presence of a flame. The flame presence
generates a micro-amp FLAME SENSE current that is monitored by the
ignition control module. A flame sense current of 0.7 micro amp (minimum)
is required to maintain burner ignition.
Power On Light................ Lit whenever the power switch (S1) is turned to ON or Cool Down mode.
Heat Light .................... Lit whenever temperature control is calling for heat.
No Ignition Light............... Lit when power is turned ON, during ignition trial & gas purge time and
when no flame is detected by flame sensor. If the oven fails to ignite after 3
attempts, it will remain lit until power is reset.
Temperature Probe ............ Senses the oven temperature for the solid state temperature control or the
computer control. On VC4GD/6D models, converts the temperature into a
resistance valve which is monitored by the temperature control board. The
probe is an RTD (resistance temperature detector) of the Thermistor type.
As temperature increases the resistance value decreases.
On VC4GC/6C models, the probe is a J type thermocouple.
Gas Valve (Dual Solenoid)....... Allows gas flow to the burner when the 1
st
valve (safety) and 2
nd
valve
(main) solenoid coils are both energized.
Cooling Fan................... Circulates cooler air from rear of oven forward to cool components in the
control area.
Mechanical Temperature Control
KX Thermostat (VC4GS/6GS) .... Regulates the oven cavity temperature by controlling the heat relay (R3)
through the blower motor centrifugal switch contacts. On ROAST & HOLD
models only, power is first connected through one set of (R4) normally
closed contacts (N.C.) then through the centrifugal switch contacts on the
motor.
Hold Thermostat (KX) .......... Holds the oven cavity temperature at 160°F after ROAST (then hold) time
expires. For the oven to operate on the Hold thermostat, the ROAST &
HOLD timer must be used and the Function Switch (S3) must be set to.
Available on models with Roast & Hold option only.