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RESIDENTIAL GAS AND ELECTRIC WATER HEATER
SERVICE HANDBOOK
A.O. Smith Water Products Company Training Department
©2002 Ashland City, Tennessee
7
Residential Gas – continued
Burner:
The burner assembly consists of the main burner, main burner orifice, main burner gas
supply tube, pilot burner, pilot burner orifice, pilot burner gas supply tube and thermocouple.
The pilot burner remains on once it is manually lit. When incoming cold water activates the
thermostat, gas flows to the main burner. The pilot flame ignites this gas. The main flame burns
until the tank reaches set temperature then the thermostat interrupts this main gas flow.
AFTER HAVING CONFIRMED THAT THE WATER HEATER HAS BEEN INSTALLED
PER THE INSTALLATION MANUAL INSTRUCTIONS:
Normal Operation
Electrical:
The Pilot Flame heats the end of a thermocouple. As the
thermocouple gets hotter, it generates a small (cannot be detected without an electrical meter)
electrical current to the bottom of the control valve. This current powers the electromagnet and
holds open the safety valve as long as the pilot flame is heating the thermocouple. DANGER! If
the pilot is extinguished, it can take up to 180 seconds for the thermocouple to cool sufficiently to
close the safety valve.