RESIDENTIAL GAS AND ELECTRIC WATER HEATER
SERVICE HANDBOOK
A.O. Smith Water Products Company
Training Department
©
2002
Ashland City, Tennessee
20
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
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.
59T4100
Combination High Limit &
Thermostat
89T 33
66T4400
Thermostat
59T4100
