Lochinvar 400-801 No Display, No Burner, Operation, Unit Does, Not Modulate, Above 50%

Service Manual

3 Troubleshooting

Table 3-1Troubleshooting Chart - No Display

FAULT	CAUSE		CORRECTIVE ACTION
	- No 120 vac supplied to unit.	•	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		board.		Connect
No Display			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 33 of this manual.
	- Main control board temperature set point	•	Review temperature setting.
	satisfied.
	- Remote thermostat satisfied.	•	Review remote thermostat setting.
No Burner	- Outside air temperature above Warm	•	Check	location of		outside	air	sensor.			Check
	Weather Shutdown (WWSD) set point for		resistance of outdoor air sensor and compare to Table
Operation	main control board.		3-2B on page 35 of this manual.
		•	Consult	display for		specific	fault.		Refer		to fault
	- Unit locked out on fault.		descriptions on page 37 of this manual for corrective
			actions.
	- Unit in Shutdown Mode.	• Take unit out of Shutdown Mode.
		•	Check ramp delay parameter settings. Optional PC
	- Ramp delay active.		software required.
		•	Turn ramp delay feature off.				See page 22 of this
Unit Does			manual for instructions on how to turn this feature off.
		• Check BMS parameter settings. Optional PC
Not Modulate	- Boiler controlled by BMS.
			software required.
Above 50%
		•	Verify that the flue sensor is located in the flue outlet.
	- Flue sensor open.	•	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.

34