Lochinvar KNIGHT 400 - 801 - Manual (Page 38)

3
Troubleshooting
Service Manual
38
Table 3-4 (continued from previous page) Troubleshooting Chart - Fault Messages Displayed on Boiler Interface
FAULT DESCRIPTION CORRECTIVE ACTION
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
XL Installation and Operation Manual for detailed
information concerning the gas supply.
• Verify that the plastic hose from the gas valve to the air
inlet is connected and is not damaged.
• Verify that the vent/air intake pipes are correctly
installed and that there are no obstructions.
• Check for 24 vac to the gas valve at the 2-pin
connection on the side of the main control board during
the ignition attempt. If no voltage is present, replace
the main control board.
• If 24 vac is present at the main control board, check
the wiring between the main control board and the gas
valve. Replace the wiring if necessary. Do not
disconnect the wiring from the gas valve and attempt to
measure voltage at that point. The main control board
can detect if the gas valve is not connected and will
display the Gas Valve or Gas Valve Fail fault.
• If 24 vac is present, check the outlet of the valve to
ensure the valve is flowing gas. With a manometer
connected to the outlet tap of the gas valve, when the
unit is in the prepurge period, there should be a
negative pressure present. When the valve is
energized a change in pressure should occur. If the
pressure change does not occur, the gas valve is not
opening. Replace the gas valve.
• Inspect flame sensor and associated wiring.
Reference page 31 of this manual for removal and
cleaning procedures. Replace if necessary.
• Inspect the burner. Reference page 31 of this manual
for removal and cleaning procedures. Replace if
necessary.
• Replace the main control board.