Table 3-1 - Troubleshooting Chart - No Display - Lochinvar KNIGHT 400 Service Manual

3
Troubleshooting
Table 3-1 Troubleshooting Chart - No Display
FAULT
- No 120 vac supplied to unit.
No Display
- No voltage through the switch.
- Bad display board.
- Bad main control board.
- Blown fuse.
- Main control board temperature set point
satisfied.
- Remote thermostat satisfied.
- Outside air temperature above Warm
No Burner
Weather Shutdown (WWSD) set point for
Operation
main control board.
- Unit locked out on fault.
- Unit in Shutdown Mode.
- Ramp delay active.
Unit Does
Not Modulate
- Boiler controlled by BMS.
Above 50%
- Flue sensor open.
34
CAUSE
Service Manual
CORRECTIVE ACTION
• Check external line switch, fuse, 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
harness at both points.
• Replace switch.
• Replace board.
• Replace the main control board.
• Replace fuse F3 on the main control board, see
page 33 of this manual.
• Review temperature setting.
• Review remote thermostat setting.
• Check location of outside air sensor.
resistance of outdoor air sensor and compare to Table
3-2B on page 35 of this manual.
• Consult display for specific fault.
descriptions on page 37 of this manual for corrective
actions.
• Take unit out of Shutdown Mode.
• Check ramp delay parameter settings. Optional PC
software required.
• Turn ramp delay feature off. See page 23 of this
manual for instructions on how to turn this feature off.
• Check BMS parameter settings.
software required.
• Verify that the flue sensor is located in the flue outlet.
• Check wiring connections at the flue sensor.
• Check the resistance of the flue sensor and compare
to Table 3-2D on page 35 of this manual.
board. Connect
Check
Refer to fault
Optional PC