A.O. Smith Water Heater HWB-520

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

Is electrical power and gas present at the valve but it does not open when system calls for heat?

Inspect boiler mounted gas controls for proper operation

Inspect boiler mounted electrical controls for proper operation

Is further inspection required based on water conditions?

Notes on any detected issues or required repairs

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 to ensure it seats properly and operates freely

Does the relief valve discharge periodically or continuously?

If yes, describe the potential cause (e.g., thermal expansion or faulty valve)

Ensure the boiler is turned off and cooled down before starting the cleaning process.

Verify that all necessary cleaning solutions and tools are available.

Drain the existing water from the system.

Inspect the drained water for contaminants and note any unusual findings.

Calculate the proper percentage of cleaning solution based on the system's water volume.

Add the calculated amount of cleaning solution to the system.

Ensure the protector switch reset button is not depressed

Remove the leads from the switch from the thermocouple function block

Attach the leads from the switch to the leads from a test flashlight

Testing with Model N22T Test Kit

Turn on the flashlight. Does the lamp light up?

Are the protector switch contacts open?

Depress reset button on switch (ensure water temperature in the boiler coils is below 200°F)