Lochinvar 402 - 2072 operation manual Sequence of operation, Operation Display

Installation & Operation Manual

7 Operating information (continued)

Sequence of operation

	OPERATION				DISPLAY
1.	The manual reset high limit must be closed before any action will			HTR:	Standby
	take place.			OUT: 123.8F(129)
2.	Upon a call for heat the control turns on the appropriate pumps			HTR:	Standby
	(system and boiler pumps for space heating; DHW pump for DHW
	call). The flow switch and low water cutoff (if equipped) must			OUT: 123.8F(129)
	close.
3.	• If the unit is equipped with a proof	of closure	valve, the
	proof of closure switch must be closed. The proof of
	closure valve is then energized.	The gas	pressure
	switch(es) (if equipped) must close.

•If the contact for the louvers is closed, the louver proving, HTR: Standby

and auto reset high limit (water heater only) inputs must close. OUT: 123.8F(129)

•If the air pressure switch is open, the prepurge cycle then begins by starting the combustion blower. Once started, the air pressure switch must close.

4.After the 15 second prepurge, the blower slows down and the hot HTR: PREPURGE

surface igniter (HSI) is energized. The HSI is heated for at least OUT: 123.9F(129) 20 seconds.

5.Once the HSI is hot, the trial for ignition begins with the HTR: IGNITION

	opening of the gas valve.	OUT: 123.9F(129)
6.	If the SMART SYSTEM control does not sense flame, then it will	HTR: POSTPURGE, LOCKOUT
	lock out.	OUT: 123.9F(129)
7.	If the SMART SYSTEM control senses flame, it will fire the burner
	to maintain the set point. The firing rate will stage as required to	HTR: RUN STG: 1
	hold the actual temperature at the set point. If the boiler lights due
	to a space heating call for heat, and the ramp delay function is	OUT: 124.8F(129)
	active (default is disabled), the staging will be held to a series of
	increasing limits after the burner has lit.

8.If the space heating call for heat is active, and a DHW call for

heat becomes active, the control will turn on the DHW pump, wait HTR: DHW STG 123

2 seconds, and then turn off the boiler pump. This will divert the OUT: 177.8(180) hot water away from the heating zone(s) and send it to the DHW

tank instead. The control will then modulate to maintain the outlet temperature to the DHW boiler set point.

9.If the DHW call for heat remains active for more than 30 minutes, and the space heating call for heat is also on, then the control will

turn on the boiler pump, turn off the DHW pump after 2 seconds, HTR: RUN STG 12

and resume firing based on the space heating set point. As long OUT: 123.0F(129) as both the space heating and DHW calls for heat remain active,

the control will switch back and forth between the two modes until one of them is satisfied.

10.Once both calls for	heat are satisfied, the control will turn	HTR: POSTPURGE
off the burner. The	blower will remain on for the 30 second
postpurge cycle. Any pumps that are running will continue to run		OUT: 127.4F(129)
for their respective pump delay times, then turn off.
11.Boiler pump off, system pump continues its delay if longer.		HTR: Standby
		OUT: 124.7F(129)
12.System pump off.		HTR: Standby
		OUT: 122.9F(129)

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