Lochinvar 402 - 2072 service manual Sequence of operation, OUT 123.8F129

Copper-fin II/IIE Boiler and Water Heater Service Manual

1 Service (continued)

Sequence of operation

Table 1A_Sequence of Operation - Space Heating and DHW

OPERATION	DISPLAY
1. The manual reset high limit must be closed before any	HTR: Standby
action will take place.	OUT: 123.8F(129)

2.Upon a call for heat the control turns on the appropriate HTR: Standby

pumps (system and boiler pumps for space heating; DHW OUT: 123.8F(129) pump for DHW call). The flow switch and low water cutoff

(if equipped) must close.

3.• The gas pressure switch(es) (if equipped) must close.

• The louver proving input must close.	HTR: Standby
• If the air pressure switch is open, the prepurge cycle then
begins by starting the combustion blower. Once started,	OUT: 123.8F(129)
the air pressure switch must close.

4. After the 15 second prepurge, the blower slows down and			HTR: PREPURGE
	the hot surface igniter (HSI) is energized. The HSI is heated
	for at least 20 seconds.		OUT: 123.9F(129)
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		HTR: POSTPURGE, PREPURGE
	it will lock out.		OUT: 123.9F(129)
7.	If the SMART SYSTEM control senses	flame,	HTR: RUN STG: 1
	it will fire the burner to maintain the setpoint.	The
	stages will fire as required to hold the actual temperature at		OUT: 124.8F(129)
	the setpoint.

8.If the space heating call for heat is active, and the DHW thermostat closes, the control will turn on the DHW pump,

wait 2 seconds, and then turn off the boiler pump. This will HTR: DHW STG 123

divert the hot water away from the heating zone(s) and send OUT: 177.8(180) it to the DHW tank instead. The control will then fire the

stages to maintain the outlet temperature to the DHW boiler setpoint.

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