Lochinvar Knight XL 399 - 800 Service Manual page 39

3
Troubleshooting
Table 3F (continued from previous page) Troubleshooting Chart - Fault Messages Displayed on Boiler Interface
FAULT
Service Blk
Low 24 VAC
Watch Dog Error
Write EEProm
CRC Parameters
No Error Stored
(continued)
DESCRIPTION
While the unit is in Service Mode, the outlet
temperature has exceeded 185°F.
120 VAC input to the main control board has
dropped below 80 VAC.
The main control board has detected an
internal fault.
The main control board has detected an
internal fault.
The main control board has detected an
internal fault.
The main control board has detected an
internal fault.
CORRECTIVE ACTION
• Establish a heating load to remove the heat from the
boiler loop.
• 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 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 boiler pump is the proper size. Reference
Section 6 - Hydronic Piping of the Knight
XL Installation and Operation Manual for boiler
pump specifications.
• Check 120 VAC supply to the transformer.
• Check wiring connections at the low voltage terminal
strip.
• Check the wire size/length to remote devices.
• Replace the transformer.
• Replace the main control board.
• Replace the main control board.
• Replace the main control board.
• Press the ENTER/RESET button on the SMART
SYSTEM display panel.
Service Manual
39