CB780E/CB784E RELAY MODULES WITH VALVE PROVING
32-00150—03
28
750-234
Run
1.
A ten-second stabilization period occurs at the
beginning of the RUN period.
2.
The firing rate motor releases to modulation.
3.
The CB780E/CB784E is now in RUN and remains in
RUN until the controller input, terminal 6, opens
(terminal 17, on VP applications), indicating that the
demand is satisfied or a limit opened.
Postpurge
The CB780E/CB784E provides a programmable (default
is 15 seconds) POSTPURGE following the completion of
the RUN period. The blower motor output remains
powered to drive all products of combustion and any
unburned fuel from the combustion chamber. It also
supplies combustion air to burn fuel being purged from
the fuel line downstream of the fuel shutoff valve.
1.
The main fuel valve, Terminals 9 and 21 (if Valve
Proving option is used), are de-energized and the
firing rate motor is commanded to the low fire
position to begin the POSTPURGE period.
2.
The Pre-Ignition Interlock closes within the first five
seconds after the demand opens.
3.
If Valve Proving option—if After, Split, or Both have
been selected, then the Valve Proving test will be
conducted concurrent with Postpurge. If Postpurge
timing remains after the Valve Proving test is com-
pleted, the Postpurge timing will complete before
going into standby.
* STANDBY and RUN can be an infinite time period.
** PURGE determined by which purge card is selected.
a
The MFEP is determined by which terminal is used.
b
If DSI is Enabled on a VP application (JR2 intact) then Ignition (terminal 10) and MV
1
(terminal 9), and MV
2
(terminal
21) are energized together. After 4 seconds terminal 10 shuts off, and system goes to Run.
c
If DSI is disabled on a VP application then MFEP is 10 seconds.
d
Default is 15 seconds. Can be programmed as long as 66 minutes.
KEYBOARD DISPLAY MODULE (KDM)
The first line of the Keyboard Display Module provides
current status of the burner sequence (STANDBY, PURGE,
PILOT IGN, MAIN IGN, RUN and POST-PURGE), timing
information (PURGE, PILOT IGN, MAIN IGN and
POSTPURGE) in minutes and seconds, hold information
(PURGE HOLD: T19) and lockout information (Lockout,
Fault Code, Message and Sequence); see Fig. 40. 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 Information,
Hn-Fault History Information, and EA-Expanded
Annunciator). 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 selectable message
supplies information for flame strength, system status
indication, system or self-diagnostics and
troubleshooting. A preemptive message will have
parentheses around the message and supply a detailed
message to support the sequence status information. A
preemptive message 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 CB780E/CB784E LEDs
provide positive visual indication of the program
sequence: POWER, PILOT, FLAME, MAIN and ALARM.
Fig. 40. Keyboard Display Module and
sequence status LEDs (Table 4).
Table 9. Sequence Timing for Normal Operation.
Device
Initiate
Standb
y
Purge
Flame Establishing
Period
Run
Post-
Purge
Timing
d
Interlock
Circuits
Firing
Rate
Circuit
Approval
Code
Bodies
Pilot
Main
a, c
CB780E/C
B784E
10 sec. *
**
4 or 10
sec.
10 or 15 sec.
b
*
15 sec. Pre-Ignition,
Lockout, High
and Low Fire
4-wire
modulatin
g
UL/CSA/F
M/IRI
Modulatin
g
203541 FIVE WIRE CONNECTOR FOR
COMMUNICATIONS, REMOTE
KEYBOARD DISPLAY AND REMOTE RESET
(NOT SUPPLIED)
SEQUENCE
STATUS
SELECTABLE
MESSAGE OR
PREEMPTIVE
MESSAGE
SEQUENCE
STATUS
LEDs
RESET
PUSHBUTTON
FLAME
SIMULATOR INPUT
FLAME CURRENT
TEST JACKS
RUN/TEST SWITCH
DI = DIAGNOSTICS
H1 = HISTORY
EA = EXPANDED
ANNUNCIATOR
CAPTIVE
MOUNTING
SCREW
PLUG-IN
PURGE
CARD
KEYBOARD
DISPLAY
MODULE
RELAY
MODULE
FLAME
AMPLIFIER
M23973B
