3
Troubleshooting
(continued)
41
Service Manual
Table 3-4 (continued from previous page) Troubleshooting Chart - Fault Messages Displayed on Boiler Interface
FAULT
DESCRIPTION
CORRECTIVE ACTION
Outlet
MRHL
(continued)
(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 manual reset high limit.
• 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.
• Check resistance of water sensors and compare to
Table 3-2A and 3-2C on page 35 of this manual.
Replace sensor if necessary.
• Replace the main control board if necessary.
Louver Proving
Sw
(will require a manual
reset once the condition
has been corrected. Press
the RESET button on the
SMART SYSTEM
display
to reset.)
An optional remote proving switch is not
making.
• Check function of remote devices.
• Check for loose or misplaced jumper if auxiliary
proving switch is not installed on the Low Voltage
Connection Board.
Fan Speed
(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 or higher
than what is being called for.
• Vent/air intake lengths exceed the maximum allowed
lengths. Refer to Section 3 - General Venting of the
Knight Wall Mount 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.
Inlet Sensor
Fault
(will require a manual
reset once the condition
has been corrected. Press
the RESET button on the
SMART SYSTEM
display
to reset.)
The control reads the inlet sensor as open
or shorted.
• Check wiring to sensor. Make sure wiring is
connected and not damaged. Reconnect / repair
wiring if necessary.
• Measure the resistance of the sensor and compare
to the resistance in Table 3-2A on page 35 of this
manual. Replace sensor if necessary.
• Replace control module.
Summary of Contents for WH 399
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