Service Manual

3Troubleshooting

Table 3-4(continued from previous page) Troubleshooting Chart - Fault Messages Displayed on Boiler Interface

FAULT

DESCRIPTION

CORRECTIVE ACTION

 

 

 

 

The main control board has received a call

• The control board will release the call for heat after a

Anti-cycling

for heat too quickly after the previous call for

set time period.

heat has ended.

 

 

• The control board will release the call for heat if the

 

 

 

 

outlet temperature drops too quickly.

 

 

 

 

The unit has failed to prove main burner

• Inspect spark electrode and associated wiring for

 

ignition after four (4) attempts.

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

Flame Fail Ign

 

connection on the side of the main control board during

 

the ignition attempt. If no voltage is present, replace

(will require a manual

 

the main control board.

reset once the condition

 

• If 24 vac is present at the main control board, check

has been corrected.

 

 

the wiring between the main control board and the gas

Press the RESET button

 

 

valve. Replace the wiring if necessary. Do not

on the SMART SYSTEM

 

 

disconnect the wiring from the gas valve and attempt to

display to reset.)

 

 

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.

 

 

 

38

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Image 38
Lochinvar 400 - 801 service manual Anti-cycling, Flame Fail Ign