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

Service Manual

3Troubleshooting

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
			harness at both points.
No Display
	- 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
Operation
	Weather Shutdown (WWSD) set point for		resistance of outdoor air sensor and compare to Table
	main control board.		3-2B on page 35 of this manual.
	- Unit locked out on fault.	•	Consult display for specific fault.					Refer	to fault
			descriptions on page 37 of this manual for corrective
			actions.
	- Ramp delay active.	•	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.
Unit Does Not
	- Boiler controlled by BMS.	• Check BMS parameter settings. Optional PC
Modulate			software required.
Above 50%
	- Flue sensor open.	•	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.

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