Turn off the Rinnai water heater. Disconnect the power cable. Allow the water heater to cool for at least one hour.
Remove the four screws holding the front panel in place. Remove the front panel.
Spray pressurized air around the main burner until all dust has been removed.
Wipe the interior of the cabinet with a soft dry cloth.
Replace the front panel and the screws that hold the panel in place.
Wipe the exterior of the cabinet with a soft dry cloth to remove all dust.