3 Troubleshooting (continued)
39
Service Manual
Table 3-4 (continued from previous page) Troubleshooting Chart - Fault Messages Displayed on Boiler Interface
FAULT DESCRIPTION CORRECTIVE ACTION
FlameSequence
(will require a manual
reset once the condition
has been corrected.
Press the RESET button
on the SMART
SYSTEM display to
reset.)
The flame detector circuit is seeing a flame
signal while no flame is present.
• Check supply voltage for proper polarity.
• Check external wiring for voltage feedback.
• Check the flame rod and make sure it is clean.
• Check the internal wiring for bad connections.
• Replace main control board.
Auto Reset High Limit
The outlet water temperature has exceeded
the setting of the automatic reset high limit.
• 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 120 vac to boiler pump motor on a call for
heat. If voltage is not present, check wiring back to
the main control board.
• Replace the main control board if necessary.
• If 120 vac is present on a call for heat and the boiler
pump is not operating, replace the pump.
• If the system pump is a variable speed pump, ensure
that the system flow is not less than the boiler flow.
• If operating on something other than an outlet sensor,
check temperature setting of the main control board.
• If the optional manual reset high limit has tripped,
check setting of the device.
• Check resistance of water sensors and compare to
Table 3-2A on page 35 of this manual. Replace
sensor if necessary.
• Replace high limit.
Fan LowORFan Speed Low
(will require a manual
reset once the condition
has been corrected.
Press the RESET button
on the SMART
SYSTEM display to
reset.)
The actual fan RPM is 30% lower than what
is being called for.
• Vent/air intake lengths exceed the maximum allowed
lengths. Refer to Section 3 - General Venting of the
Knight XL Installation and Operation Manual for
proper lengths.
• Check for obstruction or blockage in the vent/air
intake pipes or at terminations.
• Check the wiring connections at the fan and at the
main control board.
• Replace the fan.
• Replace the main control board.
Blown fuse. • Replace fuse F2 on the control board, see page 33
of this manual.