Troubleshooting - Honeywell 7800 Series Manual

b. Depress the reset button.
c. Start the system.
d. The automatic pilot valve(s) should be energized but
the pilot cannot ignite.
e. Safety shutdown will occur.
4. 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. Energize the appropriate special function input (ter-
minal 17, 19 or 20) to sequence to RUN. See the
RM7888A Sequence of Operation.
f. The flame signal should drop below 1.25 Vdc within
.three or eight seconds (depending on the FFRT of
the amplifier) after the pilot goes out.
g. Safety shutdown will occur.
5. Loss of flame during RUN.
a. Open the main fuel manual shutoff valve(s) and open
the manual pilot shutoff valve(s).
RM7888A SYSTEM DIAGNOSTICS
Troubleshooting of control system equipment failures is
easier with the RM7888A self-diagnostics and first-out
annunciation. In addition to an isolated spst alarm relay
(audible annunciation), the RM7888A provides visual an-
nunciation by displaying the ALARM LED.
Self-diagnostics of the RM7888A enable it to detect
and annunciate both external and internal system problems.
External faults such as interlock failures, flame failures and
false flame signals, are annunciated by the RM7888A lock-
out, which energizes the ALARM LED, by using the optional
Keyboard Display Module or 7800 SERIES System Annun-
ciation Diagnostics and Troubleshooting, form 65-0118.
The RM7888A provides diagnostic information to aid
the service mechanic to obtain information when trouble-
shooting the system, see Table 5 or Table 7.
The optional Keyboard Display Module displays se-
quence status messages indicating: STANDBY, PRE-
PURGE, PILOT IGN, MAIN IGN, RUN and POSTPURGE.
The selectable messages also provide visual indication,
current status and historical status of the equipment such as:
Flame Signal, Total Cycles, Total Hours, Fault History,
Diagnostic Information and Expanded Annunciator Termi-
nal Status (if used). With this information, most problems
can be diagnosed without extensive trial and error testing.
Data available in the Diagnostic Information file includes:
Device Type, Device Suffix, Software Revision, Manufac-
turing Code, Flame Amplifier Type, Flame Failure Re-
sponse Time, Selectable Jumper Configuration Status, Run/
Test Switch Status and Terminal Status.
CHECKOUT • TROUBLESHOOTING
b. Depress the reset button.
c. Start the system. Start-up should be normal and the
main burner should light normally.
d. Energize the appropriate special function input (ter-
minal 17, 19 or 20) to sequence to RUN. See the
RM7888A Sequence of Operation.
e. After the sequence is in the normal RUN period for at
least ten seconds with the main burner firing, close
the manual main fuel shutoff valve(s) to extinguish
the main burner flame.
f. The flame signal should drop below 1.25 Vdc within
.three or eight seconds after the main flame goes out.
g. Safety shutdown will occur (depending on the FFRT
of the amplifier).
IMPORTANT:
1. If the RM7888A fails to shut down on any of these
tests, take corrective action; refer to the Trouble-
shooting section and the RM7888A diagnostics and
return to the beginning of all Checkout tests.
2. When all Checkout tests are completed, reset all
switches to original states.

Troubleshooting

Diagnostic Information Index
The RM7888A with the optional Keyboard Display
Module can monitor input/output terminals and can display
the status of the terminal at the VFD (for example, Pilot
Valve T8 ON<), see S7800A1001 Keyboard Display Mod-
ule Specifications. A complete terminal description and
number are provided. The display will show the actual
status of the terminal. If voltage is detected at the terminal,
ON is displayed; but if no voltage is detected at the termi-
nal, OFF is displayed.
Historical Information Index
The RM7888A has nonvolatile memory that allows the
Relay Module to retain historical information for the six
most recent lockouts. Each of the six lockout files retains
the cycle when the fault occurred, the hour of operation
when the fault occurred, the fault message and burner status
when the fault occurred. See the S7800A1001 Keyboard
Display Module Specifications.
SERVICE NOTE: A Lockout condition or restart of an
RM7888A can be accomplished by pressing the reset
pushbutton on the RM7888A, or pressing a remote reset
pushbutton wired through an optional Keyboard Dis-
play Module, DATA CONTROLBUS MODULE™,
Extension cable Assembly, or Remote Reset Module. A
powerup reset will cause an electrical reset of the
RM7888A but will not reset a Lockout condition.
SERVICE NOTE: Remove the access slot covers on the
sides of the Q7800A,B to check voltage.
43
RM7888A
65-0175