Lochinvar KNIGHT 400 Service Manual page 40

3
Troubleshooting
Table 3-4 (continued from previous page) Troubleshooting Chart - Fault Messages Displayed on Boiler Interface
FAULT
The outlet water temperature has exceeded
Outlet ARHL
the setting of the automatic reset high limit.
Outlet MRHL
(will require a manual
reset once the condition
has been corrected.
The outlet water temperature has exceeded
Press the RESET the setting of the manual reset high limit.
button on the SMART
SYSTEM display to
reset.)
40
DESCRIPTION
Service Manual
CORRECTIVE ACTION
• Adjust the set point of the auto reset limit to a higher
setting up to a maximum of 200°F. Reference the
Knight XL Installation and Operation Manual for
adjusting procedures.
• 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
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.
sensor if necessary.
• Replace high limit.
• Adjust the set point of the manual reset limit to a higher
setting up to a maximum of 210°F. Reference the
Knight XL Installation and Operation Manual for
adjusting procedures.
• 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
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.
and Operation Manual
Replace
and Operation Manual