Watts AERCO Benchmark 2.0LN, Operating & Maintenance Instructions

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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.
154
155
C
NC
A/F VALVE
TO FRAME
HARNESS
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) Simultaneously, the ignition transformer
and the staged ignition solenoid valve
will be activated. The ignition trans-
former provides ignition spark. The
activated (open) solenoid valve allows a
small volume of gas to flow directly to
the burner assembly (Appendix F).
(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.