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33
3 Troubleshooting (continued)
Gas valve adjustment procedure
If adjustment of the gas valve is deemed necessary, use the
following procedures: (Note: The procedures below are
model specific.)
Models 150 - 285
Locate the throttle adjustment screw on the side of the venturi
valve (FIG. 3-2). Using a screwdriver, turn the screw a 1/4
turn clockwise to decrease CO
2
levels or a 1/4 turn
counterclockwise to increase CO
2
levels. After performing
one adjustment on the valve, follow the Combustion Analysis
Procedure on page 32 of this manual to measure the
combustion.
If combustion is still not within the specified range, repeat the
procedure. This procedure SHOULD NOT be performed
more than four (4) times. If after four (4) adjustments and
the combustion is still not within the specified range, revisit
the possible causes in Table 3F on page 32 or replace the gas
valve.
Figure 3-2 Gas Valve Adjustment: Models 150 - 285
Model 500
Locate the throttle adjustment screw on top of the gas valve, see
FIG. 3-4. Using a screwdriver, turn the screw a 1/4 turn
counterclockwise to increase CO
2
levels or a 1/4 turn clockwise
to decrease CO
2
levels. After one adjustment on the valve, follow
the Combustion Analysis Procedure on page 32 of this manual
to measure the combustion.
If combustion is still not within the specified range, repeat the
procedure. This procedure SHOULD NOT be performed more
than four (4) times. If after four (4) adjustments and the
combustion is still not within the specified range, revisit the
possible causes in Table 3F on page 32 or replace the gas valve.
Figure 3-4 Gas Valve Adjustment: Model 500
Model 399
Locate the throttle adjustment screw on the top of the gas
valve, see FIG. 3-3. Using a screwdriver, turn the screw 1/8
turn counterclockwise to increase CO
2
levels or 1/8 turn
clockwise to decrease CO
2
levels. After one adjustment on
the valve, follow the Combustion Analysis Procedure on page
32 of this manual to measure the combustion.
If combustion is still not within the specified range, repeat the
procedure. This procedure SHOULD NOT be performed
more than four (4) times. If after four (4) adjustments and
the combustion is still not within the specified range, revisit
the possible causes in Table 3F on page 32 or replace the gas
valve.
THROTTLE ADJUSTMENT
SCREW
Figure 3-3 Gas Valve Adjustment: Model 399