AERCO BMK 3.0 LN Dual-Fuel Series Gas Fired Low NOx Boiler System - Manual (Page 31)

CONTROL PANEL OPERATING PROCEDURES
3-9
2. The unit checks to ensure that the Proof of
Closure (POC) switch in the downstream
Safety Shut-Off Valve (SSOV) is closed.
See Figure 3-3 for SSOV locations.
PROPANE
SSOV
NATURAL
GAS SSOV
PROPANE
INLET
NATURAL
GAS INLET
TO
AIR/FUEL
VALVE
Figure 3-3.
SSOV Locations
3. With all required safety device switches
closed, a purge cycle will be initiated and the
following events will occur:
(a) The Blower relay energizes and turns
on blower.
(b) The Air/Fuel Valve rotates to the full-
open purge position and closes purge
position switch. The dial on the Air/Fuel
Valve (Figure 3-4) will read 100 to
indicate that it is full-open (100%).
(c) The VALVE POSITION bargraph will
show 100%.
4. Next, the blower proof switch on the Air/Fuel
Valve (Figure 3-5) closes. The display will
show Purging and indicate the elapsed time
of the purge cycle in seconds.
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 gas Safety Shut-Off Valve (SSOV)
is energized (opened) allowing gas to
flow into the Air/Fuel Valve.
100
DETAIL “A”
TO
B
LO
W
ER
AI
R
IN
DIAL
(DETAIL “A”)
STEPPER
MOTOR
Figure 3-4.
Air/Fuel Valve In Purge Position
BLOWER
PROOF
SWITCH
AIR/FUEL
VALVE OUTLET
TO BLOWER
Figure 3-5.
Blower Proof Switch