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3 Troubleshooting (continued)
37
Service Manual
Table 3-4 Troubleshooting Chart - Fault Messages Displayed on Boiler Interface
FAULT DESCRIPTION CORRECTIVE ACTION
Gas Pressure SW
(will require a manual
reset once the condition
has been corrected. Press
the RESET button on the
SMART SYSTEM display
to reset.)
Either the optional manual reset low gas
pressure switch or the optional manual reset
high gas pressure switch tripped.
• Reset the pressure switches.
• Measure the supply gas pressure to determine cause
of failure. Natural gas pressures should be between
4 - 14 inches w.c. and LP gas pressures
should be between 8 - 14 inches w.c.
• Refer to Section 7 - Gas Connections of the Knight
XL Installation and Operation Manual for detailed
information concerning the gas supply.
• Correct the supply gas pressure if necessary.
• Check for a loose or misplaced jumper if pressure
switches are not installed.
Flow
Switch/LWCO
(will require a manual
reset once condition has
been corrected. Press the
RESET button on the
SMART SYSTEM display
to reset.)
Either the optional flow switch or the optional
low water cutoff is not making.
• Check boiler pump operation on a call for heat.
• Check for closed valves or obstructions in the boiler
piping.
• Verify system is full of water and all air has been
purged from the system.
• Check for loose or misplaced jumpers if flow switch or
LWCO is not installed.
Blown fuse.
• Replace fuse F3 on the control board, see page 33
of this manual.
Blocked Drain SW
(will require a manual
reset once condition has
been corrected. Press the
RESET button on the
SMART SYSTEM display
to reset.)
The blocked drain switch has detected
excessive condensate build up inside the
unit.
• Check condensate tube from unit to floor drain for
proper installation and obstructions.
• Inspect condensate trap for blockage. Clean if
necessary.
• Check for loose wiring connection at wire harness
plug.
• Bad blocked drain switch. Replace switch.
APS
Open
(will require a manual
reset once the condition
has been corrected. Press
the RESET button on the
SMART SYSTEM display
to reset.)
Air pressure switch contacts are open.
• Check the wiring connections to switch. Wires should
be connected to the common and normally closed
terminals.
• 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 air
intake pipes or at terminations.
• Check reference hoses connected to the air pressure
switch for blockage or obstruction.
• Inspect the burner. Reference page 31 of this manual
for removal and cleaning procedures. Replace if
necessary.
• Inspect the heat exchanger. Reference page 32 of
this manual for removal and cleaning procedures.
Replace if necessary.
• Faulty air pressure switch. Replace switch.