72
106308-05 - 3/23
APEX Installation, Operating, & Service Instructions
Figure 9-4: Burner Flame
e. If low fire O
2
is too low (CO
2
is too high),
increase O
2
(decrease CO
2
) by turning
offset screw counterclockwise in less than
1/8 turn increments and checking the O
2
(or CO
2
) after each adjustment. If boiler is
equipped with 2 gas valves, offset screw
adjustments must be done to both gas
valves equally and simultaneously. Refer to
Figure 9-5 for location of offset screw. Verify
CO air free is less than 200 ppm.
f. If low fire O
2
is too high (CO
2
is too low),
decrease O
2
(increase CO
2
) by turning
offset screw clockwise in less than 1/8 turn
increments and checking the O
2
(or CO
2
)
after each adjustment. If boiler is equipped
with 2 gas valves, offset screw adjustments
must be done to both gas valves equally
and simultaneously. Refer to Figure 9-5 for
location of offset screw. Verify CO air free is
less than 200 ppm.
WARNING
Make sure that all adjustments at high fire are
made with the throttle, not offset screw (see
Figure 9-5). The offset screw has been factory
set using precision instruments and must never
be adjusted in the field unnecessarily.
Attempting to adjust the offset screw
unnecessary could result in damage to the
gas valve and may cause property damage,
personal injury or death.
b. If high fire O
2
is too low (CO
2
is too high),
increase O
2
(decrease CO
2
) by turning
the throttle screw clockwise in 1/4 turn
increments and checking the O
2
(or
CO
2
) after each adjustment. If boiler is
equipped with 2 gas valves, throttle screw
adjustments must be done to both gas
valves equally and simultaneously. Refer
to Figure 9-5 for location of throttle screw.
Verify CO air free is less than 200 ppm.
c. If high fire O
2
is too high (CO
2
is too low),
decrease O
2
(increase CO
2
) by turning
the throttle screw counter-clockwise in
1/4 turn increments and checking the O
2
(or CO
2
) after each adjustment. If boiler is
equipped with 2 gas valves, throttle screw
adjustments must be done to both gas
valves equally and simultaneously. Refer
to Figure 9-5 for location of throttle screw.
Verify CO air free is less than 200 ppm.
d. Lock boiler in low fire and allow fan
speed and combustion analyzer reading
to stabilize before taking combustion
readings. To lock boiler in low fire, select
High Low >> Low.
WARNING
Asphyxiation Hazard.
Offset screw is adjusted at the factory to the
specification. DO NOT touch the offset screw
if measured low fire O
2
(or CO
2
) is within limits
specified in Table 9-2 or 9-3.
Figure 9-5: Gas Valve Detail
3. Remove analyzer probe and replace cap on
boiler vent connector.
4. Return boiler to Automatic Mode. From
Operation screen, select Automatic / Manual
Firing Rate Control >> Automatic Modulation.
Select HOME to return boiler to Home Screen.
P. Test Safety Limits Controls
1. Test the ignition system safety shut-off by
disconnecting the flame sensor connector
(black plug with orange wire) from the flame
ionization electrode. See Figure 8-5. The boiler
must shut down and must not start with the
flame sensor disconnected.
9 System Start-up (continued)
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