Placing the OFF-SPRAY-BAKE switch
in BAKE provides 120 volt power
through the PLC to the bake timer
located on the remote control panel and
power to the change over damper
solenoid. The timer will begin the timing
sequence. The bake timer should be set
in the “C” mode on the left of the timer
face and the “M” mode on the right. “M”
is for minutes.
The bake delay timer supplies 120 volt
power to the PLC in the main control
panel, which begins the delay cycle. The
bake delay timer should be set for a
minimum of 5 minutes. At the
completion of the delay cycle, 120 volt
power is supplied to the change over
damper solenoid. In turn, the change
over damper is opened pneumatically
releasing the damper air valve. When the
damper valve is released, the
compressed air solenoid is de-energized
and the lighting circuit is removed from
120 v supply. This drops out the lighting
and compressed air source. The PLC
supplies 120 volt power to the gas train
power circuit.
The PLC places the temperature
controller in the second set point or 2SP.
This is the bake mode setting.
At the end of the programmed bake time,
whether 1 or 999 minutes, the PLC
initiates the shut down mode.
Shut Down
The bake timer initiates the timed shut
down mode. The supply to the change
over solenoid is also interrupted. The
change over damper closes. The lights
come back on and the temperature
controller returns to the first set position,
SP. When the burner switch is in the
summer position, the PLC shuts off the
gas train circuit.
At the end of the timed cool down cycle
(1 to 10 minutes), all functions of the
unit will shut down completely. The
PLC interrupts the 120 volt for all
components, including the exhaust fan,
intake fan, and burner circuit and holds
the unit in an “off” status until the
OFF/SPRAY/BAKE switch is set to the
OFF position. The shut down mode can
be interrupted at any time by switching
the unit to Spray.
GAS TRAIN POWER CIRCUIT
( Models 99270 )
With the OFF switch on and the SPRAY
switch in the SPRAY position and the
burner is in the WINTER position, or if
the BAKE switch is in the BAKE
position the PLC provides 120 volt
power through the Manual High Limit.
This allows 120 volt power to be
provided to the Flame Guard Device.
The Flame Guard Device starts a 7
second delay before ignition. When this
time delay is finished, both the ignition
transformer and the pilot solenoid are
energized. If the flame rod in the burner
provides proof of flame to the Flame
Guard Device, the ignition transformer is
shut down and the normally open vent
valve is closed and the main gas valves
open. After the main gas valves have
opened, the PLC closes the circuit
between the temperature control and the
gas manifold modulating valve.
If the Flame Guard Device does not
receive proof of flame in the burner
within 10 seconds, the pilot solenoid and
the ignition transformer will be de-
energized. The Flame Guard Device will
shut down the gas train.
9
Summary of Contents for 99270
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