Service Manual
3Troubleshooting (continued)
Table 3F (continued from previous page) Troubleshooting Chart - Fault Messages Displayed on Boiler Interface
FAULT | DESCRIPTION | CORRECTIVE ACTION |
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| The main control board has received a call | • The control board will release the call for heat after a | ||||
| for heat too quickly after the previous call for | set time period. |
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heat has ended. |
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| • The control board will release the call for heat if the | |||||
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| outlet temperature drops too quickly. |
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| The unit has failed to prove main burner | • Inspect spark electrode and associated wiring for | ||||
| ignition after four (4) attempts on the 399 | damage and connection. Reference page 26 of this | ||||
| model or one (1) attempt on the 500 - 800 | manual for removal and cleaning procedures. | ||||
| models. It will require a manual reset before | Replace if necessary. |
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| attempting to fire again. | • Check for proper electrical grounding of the unit. | ||||
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| • Check incoming supply gas pressure. Natural gas | ||||
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| pressures should be between 4 - 14 inches w.c. | ||||
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| (1.0 - 3.5 kPa) and LP gas pressures should be | ||||
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| between 8 - 14 inches w.c. (2.0 - 3.2 kPa). | Refer | |||
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| to Section 7 - Gas Connections of the Knight XL | ||||
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| Installation and Operation Manual for detailed | ||||
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| information concerning the gas supply. |
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| • Verify that the plastic hose from the gas valve to the air | ||||
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| inlet is connected and is not damaged. |
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| • Verify that the vent/air intake pipes are correctly | ||||
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| installed and that there are no obstructions. |
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No Flame Ign |
| • Check for 24 VAC to the gas valve at the | ||||
| connection on the side of the main control board during | |||||
(will require a manual |
| the ignition attempt. If no voltage is present, replace | ||||
reset once the condition |
| the main control board. |
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has been corrected. |
| • If 24 VAC is present at the main control board, check | ||||
Press the RESET button |
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| the wiring between the main control board and the gas | |||||
on the SMART SYSTEM |
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| valve. Replace the wiring if necessary. | Do not | ||||
display to reset.) |
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| disconnect the wiring from the gas valve and attempt to | |||||
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| measure voltage at that point. The main control board | ||||
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| can detect if the gas valve is not connected and will | ||||
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| display the Gas Valve Fail fault. |
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| • If 24 VAC is present, check the outlet of the valve to | ||||
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| ensure the valve is flowing gas. With a manometer | ||||
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| connected to the outlet tap of the gas valve, when the | ||||
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| unit is in the prepurge period, there should be a | ||||
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| negative pressure present. When the valve is | ||||
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| energized a change in pressure should occur. If the | ||||
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| pressure change does not occur, the gas valve is not | ||||
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| opening. Replace the gas valve. |
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| • Inspect flame sensor and associated wiring. | ||||
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| Reference page 26 of this manual for removal and | ||||
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| cleaning procedures. Replace if necessary. |
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| • Inspect the burner. Reference page 26 of this manual | ||||
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| for removal and cleaning procedures. Replace if | ||||
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| necessary. |
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| • Replace the main control board. |
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