Lochinvar KNIGHT 400 Service Manual page 43

3
Troubleshooting
Table 3-4 (continued from previous page) Troubleshooting Chart - Fault Messages Displayed on Boiler Interface
FAULT
Flue Sensor Fault
(will require a manual reset
once the condition has been
corrected. Press the RESET
button on the SMART
SYSTEM display to reset.)
Flue Temp Diff
(will require a manual reset
once the condition has been
corrected. Press the RESET
button on the SMART
SYSTEM display to reset.)
Flue Temp Limit
(will require a manual reset
once the condition has been
corrected. Press the RESET
button on the SMART
SYSTEM display to reset.)
Fatal Error
Memory Error
(continued)
DESCRIPTION
The control reads the flue sensor as open
or shorted.
The control module reads an excessive
temperature difference between the two
sensors.
The stack temperature has exceeded the
Flue Temp Limit set parameters.
The control module has detected parameter
settings that are out of range.
A lockout occurs at the same time as a
power outage.
Service Manual
CORRECTIVE ACTION
• Check wiring to sensor. Make sure wiring is
connected and not damaged.
wiring if necessary.
• Measure the resistance of the sensor and compare
to the resistance in Table 3-2D on page 35 of this
manual. Replace the sensor if necessary.
• Replace control module.
• Check wiring to sensor.
connected and not damaged.
wiring if necessary.
• Measure the resistance of the sensor and compare to
the resistance in Table 3-2D on page 35 of this
manual. Replace sensor if necessary.
• Restore control parameter defaults from optional PC
software.
• Replace control module.
• Inspect the heat exchanger. Reference page 32 of
this manual for the procedure on how to clean the flue
side of the heat exchanger.
• Inspect the flue sensor and associated wiring.
Measure the resistance of the flue sensor and
compare to Table 3-2D on page 35 of this manual.
Replace the sensor if necessary.
• Verify that the vent/air intake pipes are properly
installed and that there are no obstructions.
• Replace the main control board.
• Restore the parameter defaults from the optional PC
software.
• Replace control module.
• Reset control module.
Reconnect / repair
Make sure wiring is
Reconnect / repair
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