Lochinvar 151 - 801 service manual Operation, Display, A Sequence of operation, 1Service continued

Service Manual

1Service (continued)

Table 1A Sequence of operation

OPERATION DISPLAY

1.The control will turn on the water heater pump (always ON except in Night Setback). The flow switch and/or LWCO must close.

2.The control turns on power to the louver relay. The louver proving switch, air pressure switch, and blocked drain switch must close.

3.The control starts a 15 second prepurge cycle.

4.The control starts a 4 second trial for ignition by firing the spark electrode and opening the gas valve.

5.If flame is not detected within 1 second after the sparking ends, the control will perform a 10 second post-purge, then start another prepurge cycle and try to light the burner again. On the 501 and larger models, the control will lock out if this second attempt also fails. On the 400 and smaller models, the control will perform a total of 4 attempts before locking out.

6.If flame is detected, it holds the firing rate steady for 5 seconds to let the flame stabilize, then it begins to modulate the firing rate based on a set point or some other command (such as a 0-10V BMS signal).

7.Once the call for heat is satisfied, the control will turn off the burner. The blower will continue to run during a 10 second postpurge.

8.The water heater pump will continue to run for its respective pump delay time before turning off. A 60 second anti-cycle period will start, which will delay any new call for heat until it times out.

9.In Standby, ready to start a new cycle.

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