This is out of Sububans manual
Main Burner: Do not allow the burner to burn with a yellow flame, because
sooting will occur. (See Safety W arnings). If the burner flame is yellow and has an
erratic pattern, shut unit down and contact a qualified service agency. Do not
continue operating unit with improper burner flame. (See Figure 11 for correct and
incorrect burner flame appearance.)
Periodically inspect unit for soot. If soot is present anywhere on water heater,
immediately shut unit down and contact your dealer or a qualified service person.
Soot is a sign of incomplete combustion and m ust be corrected before operating
water heater. Areas to check would include:
Check for an obstruction in burner or the flue box.
Check the screen in the door to see that no foreign material has accumulated
to prevent flow of combustion and ventilating air.
Check to be sure there is no flame present at burner orifice or burner whenever
main gas valve is closed. This can be checked by turning the OFF/ON switch to
the “OFF” position.
Frequent checks should be m ade of the grommet on the gas inlet to assure
tight seal. (See “Making Gas Connections”).