Troubleshooting - Honeywell 7800 Series Manual

RM7840E,G,L,M

TROUBLESHOOTING

RM7840 SYSTEM DIAGNOSTICS
Troubleshooting of control system equipment failures is
made easier with the RM7840 self-diagnostics and first-out
annunciation. In addition to an isolated spst alarm relay
(audible annunciation), the RM7840 provides visual annun-
ciation by displaying the ALARM LED.
Self-diagnostics of the RM7840 enable it to detect and
annunciate both external and internal system problems. Ex-
ternal faults such as interlock failures, flame failures and false
flame signals, are annunciated by the RM7840 lockout,
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 RM7840 provides diagnostic information to aid the
service mechanic to obtain information when troubleshoot-
ing the system, see Table 6.
The optional Keyboard Display Module displays se-
quence status messages indicating: STANDBY, PREPURGE,
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 Terminal Status (if
used). With this information, most problems can be diag-
nosed without extensive trial and error testing. Information
available in the Diagnostic Information file 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.
Diagnostic Information Index
The RM7840 with the optional Keyboard Display Mod-
ule 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 Module Specifi-
cations. A complete terminal description and number are
provided. The display will show the actual status of the
Troubleshooting
terminal. If voltage is detected at the terminal, ON is dis-
played; but if no voltage is detected at the terminal, OFF is
displayed.
Historical Information Index
The RM7840 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 S7800A1001 Keyboard Display Module Speci-
fications.
SERVICE NOTE: A Lockout condition or restart of an
RM7840 can be accomplished by pressing the reset
pushbutton on the RM7840, or pressing a remote reset
pushbutton wired through an optional Keyboard Display
Module, DATA CONTROLBUS MODULE™, Exten-
sion cable Assembly, or Remote Reset Module. A power-
up reset will cause an electrical reset of the RM7840 but
will not reset a Lockout condition.
SERVICE NOTE: Remove the access slot covers on the
sides of the Q7800A,B to check voltage.
!
CAUTION
Reinstall access slot covers on the Q7800A,B sub-
base after performing voltage checks.
SERVICE NOTE: Maximum ambient operating tempera-
ture of a C7012E,F Series 1 through 6 will be reduced to
125° F because of the duty cycle operation of the RM7840
Relay Module.
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