RESIDENTIAL GAS AND ELECTRIC WATER HEATER
SERVICE HANDBOOK
Residential Electric – continued
Surface Mounted Thermostat (s) and High Limit (s)
The thermostats and high limits are held against the side of the tank. As the tank surface heats or
cools, a metal disc inside of the control expands or contracts to open or close electrical contacts
in the controls.
They will satisfy within 10°F of setting. The tank surface has to cool 8 - 15°F to reactivate these
controls.
Model Circuit Older Models Newer
Models1Location Temperature
Range °F
259T-Style 4100 A-6, A-7 X A-6 Upper Tank 110-170
259T-Style 4000 A-6, A-7,
C-2
X X Lower Tank 110-170
389T33 A-6 X Upper Tank 90-150
389T13 C-2, A-7 X Lower Tank 90-150
259T-Style 4000 A-6 X Lower Tank 90-150
2AW-Style 7135 A-7 X X Upper Tank 110-170
466T-Style 4400 A-6, A-7,
C-2
X X Lower Tank 190°
389T A-6, A-7,
C-2
X 170°
1”Older” = series 916 or older.
“Newer” = series 917 or more current – (Began approximately January, 1996)
2Older 59T controls had a maximum setting of 170°F. Replacement 59T controls will stop at
150°F.
389T controls are combination High Limit/Thermostat, one piece controls.
466T limits may be mounted onto 59T thermostats.
89T33 89T13
Thermostat
59T4100
66T4400
Combination High Limit &
Thermostat
59T4100
A.O. Smith Water Products Company Technical Training Department
©2005 Ashland City, TN
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