40
Servicing should only be performed by a Quali
fi
ed Service Technician
GAS VALVE ADJUSTMENT PROCEDURE
If adjustment of the gas valve is deemed necessary, use the following procedures: (
Note
: The procedures in
this section are model speci
fi
c.)
Models 150 - 285
Locate the throttle adjustment screw on the side of the venturi valve (See Figure 9). 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 39 of this
Service Handbook to measure the combustion.
If combustion is still not within the speci
fi
ed 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
speci
fi
ed range, revisit the possible causes in Table 13 on Page 39 or replace the gas valve.
Model 400
Locate the throttle adjustment screw on the top of the gas valve, see Figure 10. 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 39 of this Service
Handbook to measure the combustion.
If combustion is still not within the speci
fi
ed 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
speci
fi
ed range, revisit the possible causes in Table 13 on Page 39 or replace the gas valve.
Figure 9. Gas Valve Adjustment: Models 150 - 285
THROTTLE ADJUSTMENT
SCREW
Figure 10. Gas Valve Adjustment: Models 400
