Lochinvar ARMOR 151 - 801 Service Manual page 9

Table 1A
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.
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.
The louver
Service Manual
9