Module; Fig. 23-Keyboard Display Module And Sequence - Honeywell 7800 Series Manual

b. Main Flame Establishing Period (MFEP)
Configuration Jumper JR3 intact—RM7838B will wait
for Manual Open Valve Switch input to terminal 17
through a Manual Open Valve switch. With the con-
figuration jumper JR3 clipped and the Pilot Valve
Hold command on terminal 16 open, the RM7838B
will initiate immediate MFEP.
1. Main valve terminal 9 will be energized by RM7838B,
and the RM7838B will be in the RUN period.
2. If the configuration jumper JR2 is clipped, ten sec-
onds after terminal 9 is energized, the pilot valve
terminal 8 is de-energized. If flame is lost during
this ten second MFEP, safety shutdown will occur
and the alarm will sound.
3. If the configuration jumper JR3 is clipped, a Manual
Open Valve switch input must be present at termi-
nal 17 at the end of the ten second MFEP or safety
shutdown will occur and the alarm will sound.
RUN
1. The The RM7838B releases the firing rate motor to
modulation (terminals 13 and 15 are closed).
2. The RM7838B is now in RUN and will remain in
RUN until terminal 6 input opens (burner control opens, stop
switch is pushed, running interlocks open, a limit opens, Run/
Test switched to Test) or Pilot Valve Hold (terminal 16) is
energized.
PILOT VALVE HOLD
Pilot Valve Hold (switched line voltage input to terminal 16)
allows the burner to be cycled back to Pilot from the Run
position without the need to do a complete burner start-up.
This allows for batch loading in process applications.
Pilot Valve Hold could also be used to hold the burner
at the end of PFEP if configuration jumper JR3 has been
clipped.
A switch closure to the RM7838B terminal 16 while in the
Run position initiates the Pilot Valve Hold.
1. The RM7838B commands the firing rate motor to low
fire position.
2. Once low fire position is proven (input to terminal 18
through low fire switch) the pilot valve terminal is energized.
3. Forty five seconds later the main valve terminal is de-
energized and the ignition terminal is energized for 10 sec-
onds, then shut off.
4. Pilot valve terminal 8 remains energized throughout
Pilot Valve Hold.
5. The RM7838B will remain in Hold as long as a Pilot
Valve Hold input is present on terminal 16.
6. Opening the Pilot Valve Hold input to terminal 16 will
put the RM7838B ready to initiate MFEP.
The RM7838B will go into safety shutdown and sound
the alarm if flame is lost any time during this sequence.
NOTE: A Shutter Check Detection System must be in place
to use the Pilot Valve Hold Function. Fault 46 will occur
along with safety shutdown.
KEYBOARD DISPLAY MODULE (FIG. 22)
The first line of the vacuum fluorescent display (VFD)
provides current status of the burner sequence (STANDBY,
PURGE, PILOT IGN, MAIN IGN, and RUN), timing infor-
mation (PURGE, PILOT IGN, and MAIN IGN) in minutes
and seconds, hold information (PURGE HOLD: T19) and
lockout information (Lockout, Fault Code, Message and
Sequence). The extreme right side of the first line will either
be blank or it will show a small arrow pointing to the second
line followed by a two-letter code (DI-Diagnostic Informa-
tion, Hn-Fault History Information, and EA-Expanded An-
nunciator Diagnostic Information). When the arrow and
two-letter code are displayed, it indicates the second line is
showing a selectable message submenu. The second line
will display Selectable or Preemptive messages. A Select-
able message supplies additional information for flame
strength, system status indication, system or self-diagnostics
and troubleshooting. Preemptive messages will have paren-
theses around the message and supply a detailed message to
support the sequence status information. A preemptive mes-
sage can also be a lockout message. A preemptive message
will replace a selectable message to support the sequence
status information. It will also replace a selectable message
after 60 seconds if it or a lockout message is available. The
RM7838B LEDs provide positive visual indication of the
program sequence: POWER, PILOT, FLAME, MAIN and
ALARM.
Fig. 23—Keyboard Display Module and sequence
status LEDs (Table 3).
FIVE WIRE CONNECTOR FOR
COMMUNICATIONS, REMOTE
KEYBOARD DISPLAY AND REMOTE RESET
RUN/TEST SWITCH
SEQUENCE
STATUS
SELECTABLE
MESSAGE OR
PREEMPTIVE
MESSAGE
SEQUENCE
STATUS
LEDs
RESET
PUSHBUTTON
FLAME
SIMULATOR INPUT
27
RM7838B
OPERATION
DI = DIAGNOSTICS
H1 = HISTORY
EA = EXPANDED
ANNUNCIATOR
CAPTIVE
MOUNTING
SCREW
PLUG-IN
PURGE
CARD
KEYBOARD
DISPLAY

MODULE

RELAY
MODULE
FLAME
AMPLIFIER
FLAME CURRENT
TEST JACKS M7359
65-0120—1