13
The Bake Timer directs 120v power to then PLC and
shows as 14 on the input display in the Main Control
Panel, beginning the Shutdown mode. The power to
the changeover damper solenoid and RP relay are
interrupted. The changeover damper closes, RA are
energized, the booth lights come back on, and the
Temperature Controller returns to set point, SP, also
known as the Spray Temperature. The output from
the PLC will be de-energized shutting off the burner
if the OFF-SPRAY-BAKE switch is set to summer
position.
The PLC also begins and internal time cycle,
normally 10 minutes, all functions of the booth will
shut down completely at the end of the time cycle.
The logic of the PLC will not allow the booth to
restart until the OFF-SPRAY-BAKE switch is set to
the OFF position. The Operator may interrupt the
Shutdown Mode at any time by placing the OFF-
SPRAY-BAKE switch in the SPRAY position.
GAS TRAIN POWER CIRCUIT:
When the burner switch is set to the winter position
there will be input to terminal 4 of the PLC and will
show number 3 on the input display of the PLC. The
PLC checks to make sure that the input is at 0 on the
input display and outputs to 7 on the output display,
giving power to the low gas pressure switch. The
PLC then makes a scan of the input to 4,5, 6 & 7, on
the input screen, and then gives output to 12 on the
output display, giving power to the Fireye unit and
power to 1 on the output display giving power to the
burner green light. The PLC will have input at 8 on
the input display, showing power to the airflow
switch. When the Fireye has done its’ job there
should be power to 9 on the input screen, showing
that power has been given to the vent and blocking
valves on the gas train. The PLC will also make the
signal connection 0 on the output display, making
the connection between the gas modulating valve
and the temperature control. In the event the Fireye
goes into the alarm state, there will be input to 10 on
the input display and no input to 9 on the PLC input
display. There will also be output to 2 on the output
display, giving power to the burner red light and the
output to 1 on the display, discontinuing the
power to the burner green light.
The Low Gas and High Gas Limit, the Proof
of Closure switch (all three are located on the
gas train), the High Temperature switch
(located on the roof of the cabin) or the Air
Flow switch (Intake Pressure switch). Each of
these items may be checked by proving 110
volts from their respective terminals at the top
of the Main Control Panel. The airflow switch
(intake pressure switch) is powered through
the flame safety module, and has two
terminals.
The flame safety module will give an alarm
state (lighting the red burner light) for one of
three reasons. One, there is no spark in the
burner to ignite the burner pilot. Two, there is
no fuel being delivered to the pilot to create a
flame. Three, the flame guard device is not
sensing that there is flame in the burner.
COMPRESSED AIR FOR SPRAY
APPLICATIONS WITHIN BOOTH:
A solenoid is provided to control compressed
air in the booth. It is located within the Main
Control Panel. 110v power is provided to the
solenoid through the PLC output 5 on the
display. For the PLC to output at 5, the RA air
over electric switch, Door air switch, and
exhaust pressure switch must be closed giving
power to the PLC input 12.
