Service Manual
3Troubleshooting
Table 3A Troubleshooting Chart - No Display
FAULT | CAUSE |
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| - No 120 VAC supplied to unit. | • | Check external line switch, fuse, or breaker. |
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| • | Check position of ON/OFF switch. Turn switch to the | |||||
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| ON position. |
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| • Check 120 VAC through the ON/OFF switch. |
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| • Check | wiring | harness | connection | between | display | |
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| board | and | main | control board. | Connect | |
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| harness at both points. |
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No Display |
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- No voltage through the switch. | • | Replace switch. |
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| - Bad display board. | • | Replace board. |
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| - Bad main control board. | • | Replace the main control board. |
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| - Blown fuse. | • | Replace fuse F3 on the main control board, see | |||||
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| page 21 of this manual. |
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| - Main control board temperature set point | • | Review temperature setting. |
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| satisfied. |
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No Burner |
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- Remote thermostat satisfied. | • | Review remote thermostat setting. |
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Operation |
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| - Unit locked out on fault. | • | Consult display for specific fault. | Refer | to fault | |||
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| descriptions on page 25 of this manual for corrective | |||||
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| - Water heater controlled by BMS. | • | Check BMS parameter settings. Optional PC software | |||||
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Unit Does Not |
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- Flue sensor open. | • | Verify that the flue sensor is located in the flue outlet. | ||||||
Modulate Above |
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50% |
| • | Check wiring connections at the flue sensor. |
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| • Check the resistance of the flue sensor and compare | ||||||
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| to Table 3C on page 23 of this manual. |
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22 
