CB780/CB784 RELAY MODULES
32-00207—01
34
1.
Opening a Preignition Interlock during STANDBY or
PREPURGE period.
a. *Preignition ILK* fault will be displayed on the
VFD. Fault code 10 or 33 will be displayed to
denote the fault.
b. Safety shutdown will occur.
2.
Opening a Lockout Interlock during PREPURGE,
PILOT IGN, MAIN IGN or RUN period.
a. *Lockout ILK* fault will be displayed on the VFD.
Fault code 11 or 12 or 21 or 29 will be displayed
to denote the fault.
b. Safety shutdown will occur.
3.
Detection of flame 40 seconds after entry to STAND-
BY, fault code 9. Detection of flame ten seconds into
Drive to Purge Rate or during measured PREPURGE
time.
a. Simulate a flame to cause the flame signal volt-
age level to be at least 1.25 Vdc for 40 seconds
after entry to STANDBY and also simulate a
flame signal for 10 seconds during PREPURGE.
b. *Flame Detected* fault will be displayed on the
VFD. Fault code 9 or 15 or 18 will be displayed to
denote the fault.
c. Safety shutdown will occur.
4.
Failure to ignite pilot.
a. Close pilot and main fuel manual shutoff
valve(s).
b. Depress the reset button.
c. Start the system.
d. The automatic pilot valve(s) should be energized
but the pilot cannot ignite.
e. *Pilot Flame Fail* fault will be displayed on the
VFD. Fault code 28 will be displayed four or ten
seconds (depending on the jumper configuration
selection for PFEP) after the pilot valve(s) is
energized to denote the fault.
f.
Safety shutdown will occur.
5.
Failure to ignite main.
a. Open the manual pilot valve(s); leave the main
fuel manual shutoff valve(s) closed.
b. Depress the reset button.
c. Start the system.
d. The pilot should ignite and the flame signal
should be at least 1.25 Vdc but the main burner
cannot light.
e. The flame signal should drop below 1.25 Vdc
within 3 seconds after the interrupted pilot goes
out.
f.
*Main Flame Ign.* fault will be displayed on the
VFD. Fault code 19 will be displayed to denote
the fault.
g. Safety shutdown will occur.
6.
Loss of flame during RUN.
a. Open the main fuel manual shutoff valve(s) and
open manual pilot shutoff valve(s).
b. Depress the reset button.
c. Start the system. Start-up should be normal and
the main burner should light normally.
d. After the sequence is in the normal RUN period
for at least ten seconds with the main burner fir-
ing, close the manual main fuel shutoff valve(s)
to extinguish the main burner flame.
e. The flame signal should drop below 1.25 Vdc
within 3 seconds after the main flame goes out.
f.
*Main Flame Fail* fault will be displayed on the
KDM. Fault code 17 will be displayed to denote
the fault.
g. Safety shutdown will occur.
7.
Opening a Preignition Interlock after the first five
seconds of POSTPURGE.
a. *Preignition ILK* fault will be displayed on the
KDM. Fault code 33 will be displayed to denote
the fault.
b. Safety shutdown will occur.
IMPORTANT:
1. If the CB780/CB784 fails to shut down on any of
these tests, take corrective action; refer to
CB780/CB784 Troubleshooting and diagnostics
manual and return to the beginning of all Check-
out tests.
2. When all Checkout tests have been completed,
reset all switches to original status.
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 (audible annunciation), the CB780/CB784
provides visual annunciation by displaying a fault code
and fault or hold message at the Keyboard Display
Module. The CB780/CB784 provides118 diagnostic
messages for troubleshooting the system (see the
CB780/CB784 System Annunciation Diagnostics and
Troubleshooting, Bulletin Number CB-7803.
Self-diagnostics of the CB780/CB784 enables it to detect
and annunciate both external and internal system
problems. Internal faults and external faults such as
interlock failures, flame failures and false flame signals
are annunciated by the CB780/CB784, which energizes
the ALARM LED or visually displayed at the Keyboard
Display Module.
The KDM displays a sequence status message indicating:
STANDBY, 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 diagnosed without
extensive trial and error testing.
Table 4 provides the sequence and status hold messages.
Table 10 provides a summary of all CB780/CB784 fault
messages and fault codes. In addition, Diagnostic
Information and History Data are available to assist in
troubleshooting the CB780/CB784, see Table 6.
The CB780/CB784 provides diagnostic information to aid
the service mechanic in obtaining information when
troubleshooting the system, see Tables 4, 5, 6 and 10.
Information available in the Diagnostic Information
includes Device Type, Device Suffix, Software Revision,
Manufacturing Code, Flame Amplifier Type, Flame Failure
Response Time, Selectable Jumper Configuration Status,
Run/Test Switch Status and Terminal Status.
