28
Servicing should only be performed by a Quali
fi
ed Service Technician
5. The water heater is shipped with three (3) spare fuses in a plastic bag attached to the control module
cover.
6. If necessary, replace open fuse (F3 is .80 amps, F2 is 3.15 amps, and F1 is 5 amps).
Note:
Fuses F1, F2 and F3 are all slow blow fuses.
Do not jumper fuse or replace with any fuse except as speci
fi
ed. Failure to comply could result in severe
personal injury, death, or substantial property damage.
7. Install control module cover and top access cover after fuse inspection.
8. Restore power to the water heater at the external line switch and verify water heater operation (Start-up
section in the XP Water Heater Instruction Manual) after completing water heater service.
TROUBLESHOOTING CHART - NOT VISIBLE ON DISPLAY
Table 8. Troubleshooting Chart - Not Visible On Display
FAULT
CAUSE
CORRECTIVE ACTION
No Display
- No 120 VAC supplied to unit.
• Check external line switch, or breaker.
• Check position of ON/OFF switch. Turn
switch to the ON position.
• Check 120 VAC through the ON/OFF
switch.
• Check wiring harness connection
between display board and main control
board. Connect harness at both points.
- No voltage through the switch.
• Replace switch.
- Bad display board.
• Replace board.
- Bad main control board.
• Replace the main control board.
- Blown fuse.
• Replace fuse F3 on the main control
board, see Page 27 of this Service
Handbook.
No Burner Operation
- Main control board temperature
set point satis
fi
ed.
• Review temperature setting.
• Check display for Standby status.
- Remote thermostat satis
fi
ed.
• Review remote thermostat setting.
- Unit locked out on fault.
• Consult display for speci
fi
c fault. Refer
to fault descriptions on Pages 28 - 37
of this Service Handbook for corrective
actions.
• Check Current Fault section in Display
Menu.
Unit Does Not
Modulate Above 50%
- Water heater controlled by BMS. • Check BMS parameter settings.
- Flue sensor open.
• Verify that the
fl
ue sensor is located in
the
fl
ue outlet.
• Check wiring connections at the
fl
ue
sensor.
• Check the resistance of the
fl
ue sensor
and compare to Table 11.2 on Page 38
of this Service Handbook.