750-166 2-1
FIVE WIRE CONNECTOR FOR
COMMUNICATIONS, REMOTE
KEYBOARD DISPLAY AND REMOTE RESET
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
M7395
Table 1 provides the sequence and status hold messages.
Table 6 provides a summary of all CB780/CB784 fault
messages and fault codes. In addition, Diagnostic Informa-
tion and History Data are available to assist in troubleshoot-
ing the CB780/CB784, see Table 2.
The CB780/CB784 provides diagnostic information to
aid the service mechanic in obtaining information when
troubleshooting the system, see Tables 1, 2, 3 and 4. Infor-
mation available in the Diagnostic Information includes
Device Type, Device Suffix, Software Revision, Manufac-
turing Code, Purge Time, Flame Amplifier Type, Flame
Failure Response Time, Selectable Jumper Configuration
Status, Run/Test Switch Status and Terminal Status.
Diagnostic Information Index
The CB780/CB784 monitors input/output terminals and
can display the status of the terminal at the KDM (example:
Pilot Valve T8 1 (one), see Table 3. A complete terminal
description and terminal number are provided. The display
shows the actual status of the terminal. If voltage is detected
at the terminal, 1 (one) is displayed; but if no voltage is
detected at the terminal, 0 is displayed; see Table 3.
Section 2 - CB780/CB784
System Annunciation
Diagnostics and Troubleshooting
CB780/CB784 SYSTEM DIAGNOSTICS
Troubleshooting control system equipment failures is
made easier with the CB780/CB784 self-diagnostics and
first-out annunciation. In addition to an isolated spst alarm
relay (for audible annunciation), the CB780/CB784 pro-
vides visual annunciation by displaying a fault code and fault
or hold message at the Keyboard Display Module (standard
on CB780, optional on CB784) 2 row by 20 column Vacuum
Fluorescent Display (VFD). The CB780/CB784 provides
127 different diagnostic messages for troubleshooting the
system.
Self-diagnostics of the CB780/CB784 enables it to detect
and annunciate both external and internal system problems.
Internal faults and external faults (e.g., interlock failures,
flame failures, and false flame signals) are annunciated by
the CB780/CB784, through the Device ALARM LED Alarm
output, and can be visually displayed at the Keyboard Dis-
play Module (KDM).
The KDM displays a sequence status message indicat-
ing: STANDBY, SAFE START CHECK, PREPURGE,
PILOT IGN, MAIN IGN, RUN and POSTPURGE. The
selectable messages also provide visual indication of current
status and historical status of the equipment such as: Flame
Signal, Total Cycles, Total Hours, Fault History, Diagnostic
Information and Expanded Annunciator terminal status (if
used). With this information, most problems can be diag-
nosed without extensive trial and error testing.
*
*NOTE: Remote Reset must be mounted within sight
of the boiler control panel.
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