Vulcan-Hart VC4G Service Manual page 52

VC4G & VC6G SERIES FULL SIZE CONVECTION OVENS - ELECTRICAL OPERATION
occurs: ROAST & HOLD timer is turned OFF; function
switch (S3) is turned back to Normal ROAST (normal
cooking) or Power switch (S1) is turned to the OFF or
COOL DOWN position..
1. With the power switch turned ON, power is
supplied to timer.
2. Set ROAST & HOLD timer to desired time (Roast
& Hold cooking).
NOTE: To Roast then Hold the cooked product at a
fixed temperature, the Roast & Hold timer must be
used and the function switch (S3) must also be set to
Roast & Hold as indicated under step1 conditions for
the Roast & Hold cycle.
A. Contacts 1 & 3 close, timer motor is
energized and timing "down" begins.
3. Time expires on Roast & Hold timer.
A. Contacts 1 & 3 open, timer motor is de-
energize and timing stops.
B. Contacts 1 & 4 close.
1) If the oven was heating, then the gas
burner and heat light go out; If the oven
was not heating, then the gas burner
and heat light remain out.
NOTE: The Temperature control board remains
powered and the internal relay contacts remain closed
as long as oven cavity temperature is below the 175°F
minimum set point temperature of the board and
power is ON.
2) Power is connected through function
switch (S3) --- Hold relay (R2) is then
energized, R2 contacts change state
and the normally open (N.O.) contacts
close.
a. Power to one side of hold
thermostat.
NOTE: When temperature is above 160°F (±12) the
hold thermostat contacts are open.
3) Motor speed relay (R1) de-energized,
(R1) contacts change state and the
normally open (N.O.) contacts OPEN.
a. Convection fan motor stops and
centrifugal switch (N.O.) on motor
OPENS.
a)
NOTE: This is considered second stage cooking in
the ROAST & HOLD cycle where the stored heat in
the oven continues to cook the product.
F24682 Rev. D (1016)
Heat relay (R3) de-energize,
relay (R3) contacts open and
oven heating stops.
4. Oven temperature falls below 160°F (±12) and
hold thermostat contacts close.
A. Heat light comes ON.
B. Motor speed relay (R1) is energized, (R1)
contacts change state and the normally
open (N.O.) contacts CLOSE.
1)
C. Power is also applied to one side of the
centrifugal switch on the convection fan
motor through the temperature control
internal relay (N.O.) contacts.
D. When the convection fan motor reaches
operating speed, the centrifugal switch on
the motor closes.
1)
5. Oven reaches the "fixed" hold temperature and
hold thermostat opens.
A. Heat light goes out.
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Convection fan motor energized (fan
speed low).
Heat relay (R3) is energized.
a. Heat relay (R3) contacts (N.O.)
close and
a) Ignition module is energized.
b) No ignition light (red) comes
ON, module performs a self
diagnostic test for 4 seconds,
2nd valve (main) on the gas
valve is energized. Gas
starts to flow to the burner,
sparking begins, the NO
IGNITION light goes out and
burner lights. Sparking
continues for up to 7 seconds
or until a flame is
established. If a flame is
SENSED, the NO IGNITION
light stays out and burner
remains lit.
If a flame is not SENSED
after 7 seconds of sparking,
the NO IGNITION light
comes back on, 2nd valve
(main) on the gas valve is de-
energized and gas flow to the
burner stops. Ignition trial
cycle repeats after a 15
second purge between
cycles for two additional tries
before locking out. To reset
after a lockout, turn power
switch (S1) OFF then ON.