RESIDENTIAL GAS AND ELECTRIC WATER HEATER
SERVICE HANDBOOK
Residential Electric – continued
Since the element (s) are - very nearly - totally immersed in the tank, thermal efficiency is
assumed to be 100%. – all of the Btu (Watts) generated, enter the water.
B. A. C.
• Watt Density = the density of the wattage output of the element compared to the surface
area of the element (i.e. “High Watt Density Element” will have the most wattage per square
inch of element surface. If the above elements generated 4,500 w. each, “B” might be
considered a “high” watt density element, “A” a medium and “C” a low.)
• Voltage Notes:
120 volt AC circuit
240 volt AC circuit
(
Hot
)
L1 L2
(
Hot
)
(
Hot
)
L1 L2
L1 to Ground = 120 Volts
L2 to Ground = 0 Volts
L1 or L2 to Ground = 120 Volts
L1 L2 = 240 Volts
A.O. Smith Water Products Company Technical Training Department
©2005 Ashland City, TN
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