Troubleshooting - Honeywell 7800 Series Product Data

7800 SERIESS7800A2142 4-Line LCD Keyboard Display Module
The lines are scrollable using the up and down arrows. For lines that navigate to another
page the right arrow or OK button is pressed when the line has input focus (highlighted) to
go to the new page.

TROUBLESHOOTING

After the KDM is installed, return the 7800 SERIES to normal operation, restore power
and run the system through at least one complete automatic cycle. For complete
Troubleshooting and System Checkout information, see form 65-0229.
7800 SERIES System Diagnostics
Troubleshooting control system equipment failures is made easier with the 7800 SERIES
self-diagnostics and first-out annunciation. The S7800 provides visual annunciation by
displaying a fault code and fault or hold message on the display.
Self-diagnostics of the 7800 SERIES 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 KDM via the 7800 SERIES
Relay Module.
The KDM displays a sequence status message indicating STANDBY, PREPURGE, PRE-
IGNITION, SAFETY 1, PILOT IGN, PILOT STAB., MAIN IGN, RUN or POSTPURGE, as
appropriate. 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 3 provides the sequence and status hold messages. These messages along with the
fault messages (Table 5) can be viewed on-line in the KDM.
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