Submittal Sheet

7800 SERIES S7800A2142 KEYBOARD DISPLAY MODULE
11 32-00110—05
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.
Table 3. Keyboard Display Module Sequence and Status Hold Messages .
Sequence Status
INITIATE mm:ss The Keyboard Display Module (KDM) indicates the burner status, INITIATE, a stabilization period
for the relay module to check for any fluctuations in ac line voltage inputs or control inputs on
power up or during normal operation. The timing of the INITIATE period is either two seconds or
ten seconds, depending on the model, before entering STANDBY.
If the relay module is in an INITIATE HOLD status, the following conditions could exist:
INITIATE HOLD:
(AC Frequency/Noise)
The KDM indicates the burner status and that it is waiting for excess line noise to clear up, which
prevents sufficient reading of the line voltage inputs. The burner sequence does not advance
into STANDBY until the excess line noise ceases or a line frequency error occurs; this is caused
by using a 60 Hz device on a 50 Hz line, or vice versa on devices with a date code earlier than
9804, is corrected.
INITIATE HOLD:
(AC Line Dropout)
The KDM indicates the burner status and that ac line power has momentarily dropped out. The
burner sequence does not advance into STANDBY until the ac line voltage has stabilized
throughout the INITIATE sequence.
INITIATE HOLD:
(AC Frequency)
The KDM indicates the burner status and that line frequency is faster than the expected value.
The burner sequence does not advance into STANDBY until the line frequency returns to the
proper value; this is perhaps caused by using a 60 Hz device on a 50 Hz line for devices with a
date code earlier than 9804.
INITIATE HOLD:
(Low Line Voltage)
The KDM indicates the burner status and that low line voltage (10% lower than rated voltage)
has occurred. The burner sequence does not advance into STANDBY until the line voltage is at a
sufficient level for proper operating parameters.
STANDBY The KDM indicates the burner status, STANDBY. The burner can be placed in STANDBY by
opening the burner switch or if the operating controller indicates its setpoint is satisfied. If a
demand is present for burner operation, the burner sequence does not advance from STANDBY
to PURGE until the recycle limits close. If an Expanded Annunciator is connected, the display
messages are enhanced.
If the relay module is in a STANDBY HOLD status, the following conditions could exist:
STANDBY HOLD:
F/G (Flame Detected)
The KDM indicates the burner status and that a flame is detected. A demand is present for
burner operation. The sequence does not advance to PREPURGE until the flame signal clears. If
the flame signal does not clear within 40 seconds, the relay module locks out.
STANDBY HOLD: T20
(Pre-Ignition Interlock)
The KDM indicates the burner status and that the Pre-Ignition Interlock is not closed. A demand
is present for burner operation, but the burner sequence does not advance to PREPURGE until
the Pre-Ignition Interlock proves closed. If this time exceeds a 30 second hold, the relay module
locks out.