3
Troubleshooting
Service Manual
38
Table 3-4 (continued from previous page) Troubleshooting Chart - Fault Messages Displayed on Boiler Interface
FAULT
DESCRIPTION
CORRECTIVE ACTION
APS / HEX
Temp Sw
Open
(will require a manual
reset once the condition
has been corrected.
Press the RESET button
on the SMART SYSTEM
display to reset.)
Either the air pressure switch contacts are
open, or the O-temp heat exchanger switch
has opened.
APS:
• 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 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.
O-TEMP HEX SWITCH
(Applies to the 286 Model Only):
• Inspect the back of the inner combustion chamber at
burner level for refractory breakdown / missing.
Replace heat exchanger if refractory is broken and unit
has fired.
• Check continuity across two contacts. Wires should be
connected at both poles of the normally closed switch.
• Faulty O-Temp HEX Switch. Replace switch.
Anti-cycling
The main control board has received a call
for heat too quickly after the previous call for
heat has ended.
• The control board will release the call for heat after a
set time period.
• The control board will release the call for heat if the
outlet temperature drops too quickly.
Flame Fail Ign
(will require a manual
reset once the condition
has been corrected.
Press the RESET button
on the SMART SYSTEM
display to reset.)
The unit has failed to prove main burner
ignition after four (4) attempts.
• Inspect spark electrode and associated wiring for
damage and connection. Reference page 31 of this
manual for removal and cleaning procedures.
Replace if necessary.
• Check for proper electrical grounding of the unit.
• Check incoming supply gas pressure. 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
Boiler Installation and Operation Manual for detailed
information concerning the gas supply.
