Service Manual

3 Troubleshooting (continued)
Service Manual
35
Table 3F (continued from previous page) Troubleshooting Chart - Fault Messages Displayed on Boiler Interface
FAULT DESCRIPTION CORRECTIVE ACTION
Adjustable High
Limit w/Manual
Reset
(will require a manual
reset once the condition
has been corrected. Press
the RESET button on the
SMART SYSTEM display
to reset.)
The outlet water temperature has exceeded
the setting of the 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.
• Check voltage to 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.
• If the system pump is a variable speed pump, ensure
that the system flow is not less than the boiler flow.
• If operating on either an inlet or system supply sensor,
check temperature setting of the main control board.
• If the high limit has tripped, check setting of the
device.
• Check resistance of water sensors and compare to
Table 3B on page 30 of this manual. Replace sensor
if necessary.
• Replace high limit.
Fan Low
OR
Fan 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 F4 on the control board, see page 28 of
this manual.