Lochinvar KNIGHT 399 - Manual (Page 37)

3
Troubleshooting
(continued)
Service Manual
37
Table 3F (continued from previous page) Troubleshooting Chart - Fault Messages Displayed on Boiler Interface
FAULT DESCRIPTION CORRECTIVE ACTION
Temp O/Shoot
The stack temperature has exceeded the set
parameters for the boiler.
• Inspect the heat exchanger. Reference page 27 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 3C on page 30 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.
The temperature rise across the heat
exchanger has exceeded the set parameters
for the boiler.
• Verify that the system is full of water and that all air
has been properly purged from the system.
• Verify that the boiler is piped properly into the heating
system. Refer to Section 6 - Hydronic Piping of the
Knight XL Installation and Operation Manual
for the proper piping methods for the Knight XL boiler.
• Check for voltage to the boiler pump motor on a call
for heat. If voltage is not present, check the wiring
back to the pump relay. Replace the pump relay if
necessary.
• If 120 VAC is present on a call for heat and the boiler
pump is not operating, replace the pump.
• Verify that the boiler pump is set to the proper speed
or that the pump is the proper size. Reference
Section 6 - Hydronic Piping of the Knight
Boiler Installation and Operation Manual for boiler
pump specifications.
Outlet water temperature has exceeded the
maximum outlet water temperature. • Verify that the system is full of water and that all air
has been properly purged from the system.
• Verify that the boiler is piped properly into the heating
system. Refer to Section 6 - Hydronic Piping of the
Knight XL Installation and Operation Manual
for the proper piping methods for the Knight XL boiler.
• Check for voltage to the boiler pump motor on a call
for heat. If voltage is not present, check wiring back
to the pump relay. Replace the pump relay if
necessary.
• If 120 VAC is present on a call for heat and the boiler
pump is not operating, replace the pump.