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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 10F of setting. The tank surface has to cool 8 - 15F to reactivate these
controls.
Model Circuit Older Models
Newer
Models
1
Location
Temperature
Range °F
2
59T-Style 4100
A-6, A-7 X A-6 Upper Tank 110-170
2
59T-Style 4000
A-6, A-7,
C-2
X X Lower Tank 110-170
3
89T33
A-6 X Upper Tank 90-150
3
89T13
C-2, A-7 X Lower Tank 90-150
2
59T-Style 4000
A-6 X Lower Tank 90-150
2
AW-Style 7135
A-7 X X Upper Tank 110-170
4
66T-Style 4400
A-6, A-7,
C-2
X X Lower Tank 190°
3
89T
A-6, A-7,
C-2
X 170°
1
”Older” = series 916 or older.
“Newer” = series 917 or more current – (Began approximately January, 1996)
2
Older 59T controls had a maximum setting of 170°F. Replacement 59T controls will stop at
150°F.
3
89T controls are combination High Limit/Thermostat, one piece controls.
4
66T 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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