Gas Valve Adjustment Procedure - A.O. Smith XWH 150 Service Handbook

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 specifi 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
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 specifi 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
specifi 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
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 specifi 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
specifi ed range, revisit the possible causes in Table 13 on Page 39 or replace the gas valve.
40
2
Figure 9. Gas Valve Adjustment: Models 150 - 285
Figure 10. Gas Valve Adjustment: Models 400
Servicing should only be performed by a Qualifi ed Service Technician
levels or a 1/4 turn counterclockwise to increase CO
levels or 1/8 turn clockwise to decrease CO
2
THROTTLE ADJUSTMENT
SCREW
levels.
2
levels.
2