AERCO BMK 3.0 LN Nat. Gas APRIL 2009 - Manual (Page 31)

CONTROL PANEL OPERATING PROCEDURES
5. Upon completion of the purge cycle, the
Control Box initiates an ignition cycle and
the following events occur:
(a) The Air/Fuel Valve rotates to the low-
fire ignition position and closes the
ignition switch. The dial on the Air/Fuel
Valve (Figure 3-6) will read between 25
and 35 to indicate that the valve is in
the low-fire position.
(b) The igniter relay is activated and
provides ignition spark.
(c) The staged ignition solenoid valve is
energized (opened) allowing gas to flow
through the staged ignition assembly.
(d) The gas Safety Shut-Off Valve (SSOV)
is energized (opened) allowing gas to
flow into the Air/Fuel Valve.
25
DIAL
(DETAIL “A”)
STEPPER
MOTOR
DETAIL “A”
Figure 3-6.
Air/Fuel Valve In Ignition Position
6. Up to 7 seconds will be allowed for ignition
to be detected. The igniter relay will be
turned off one second after flame is
detected.
7. After 2 seconds of continuous flame, Flame
Proven will be displayed and the flame
strength will be indicated. After 5 seconds,
the current date and time will be displayed in
place of the flame strength.
8. With the unit firing properly, it will be
controlled by the temperature controller
circuitry. The boiler’s FIRE RATE will be
continuously displayed on the front panel
bargraph.
Once the demand for heat has been satisfied,
the Control Box will turn off the dual SSOV gas
valves. The blower relay will be deactivated and
the Air/Fuel Valve will be closed. Standby will
be displayed.
3.9 START/STOP LEVELS
The start and stop levels are the fire rate
percentages that start and stop the unit, based
on load. These levels are Factory preset as
follows:
Start Level: 20%
Stop Level: 14%
Normally, these settings should not require
adjustment.
Note that the energy input of the boiler is not
linearly related to the fire rate percentage
(Air/Fuel Valve position). Refer to Table 3-6 on
the following page for the relationship between
the energy input and fire rate percentage.
3-9