A.O. Smith Water Heater HWB-670 Natural

Turn off the electrical power, main manual gas shutoff, and pilot valves (if applicable).

Allow boiler parts and vent to cool before disassembly.

Remove the boiler draft diverter and vent pipe running to the chimney.

Check parts and chimney for obstructions and clean as necessary.

Remove burner from boiler and other metal parts as required to clean and vacuum the heat exchanger and combustion coils.

Refer to parts list supplied with this manual for disassembly aid.

Ensure a drain line is attached to the valve to direct discharge to an open drain

Lift the lever at the end of the valve several times

Did the valve seat properly and operate freely?

Is the valve discharging periodically or continuously?

Identify possible causes if the valve is discharging

Pilot Burner - Electronic Ignition

Open fused disconnect switch or shut off electrical power to the boiler.

Turn the gas valve control knob counterclockwise to the 'PILOT' position.

Close fused disconnect switch to restore electrical power to the boiler.

Did the pilot ignite with the combination gas valve knob set at 'PILOT' and the system calling for heat?

Adjust pilot flame to cover 3/8" to 1/2" (10-12mm) of the sensing probe tip.

Did the main burner fail to light after pilot ignition?

Check the following if the main burner fails to light

Replace valve if electrical power and gas are present but the valve does not open when system calls for heat.

Ensure the boiler is not connected to a common vent or chimney with solid fuel burning equipment.

Verify that the equipment room is not under negative pressure.

Inspect the venting system for the following issues

Is there sufficient supply and ventilation air in the equipment room?

Confirm that no unsafe conditions were identified during the inspection.

Main Burner Characteristics Check

Verify main burner characteristics

Is there any accumulation of lint or foreign material blocking air openings?

Is there good flow of combustion and ventilating air to the unit?

Maintain a clear area around the boiler

Turn off electrical power and close the main manual gas shutoff valve

Allow boiler parts to cool before disassembly

Remove main burner manifold assembly from boiler