Watts AERCO Benchmark 2.0, User Manual

Page: 28 / 97

CONTROL PANEL OPERATING PROCEDURES
3-8
(a) Blower relay energizes and turns on
blower.
(b) Air/Fuel Valve rotates to 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 FIRE RATE bargraph will show
100%.
STEPPER
MOTOR
DIAL
(DETAIL "A")
BURNER
BLOWER
DETAIL "A"
100
Figure 3-4.
Air/Fuel Valve In Purge Position
4. Next, the blower proof switch (Figure 3-5)
closes. The display will show Purging and
indicate the elapsed time of the purge cycle
in seconds. The normal (default) time for the
purge cycle is 7 seconds.
HARNESS
155
C NO
154
TO FRAME
A/F VALVE
Figure 3-5.
Blower Proof Switch
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.
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.