Product Specifications

Combination Control for Electric Water Heaters

The 89T series controls are designed to meet the high electrical loads and long life requirements of electric water heaters. The 89T combines the temperature control and temperature limit thermostats into a single housing with a small footprint and low profile. Both switches use a temperature sensitive bimetal disc to provide high-speed, snap-action contact separation for a long, dependable life.

Features and Benefits

• An automatic reset control which is adjustable over a 60°F (33°C) range. Lowest calibration of the adjustable range may be specified from 90°F to 140°F (32°C to 60°C).

• A manual reset control which operates at a factory calibrated temperature which may be specified between 160°F (71°C) and 220°F (104°C).

• The 89T mounting tabs snap into the customer’s bracket to mount the thermostat to the water tank. The 89T is interchangeable with brackets used on the Therm-O-Disc 59T/66T controls.

Switch Actions

SPST – The switch opens normally closed contacts on temperature rise and automatically recloses the contacts when temperatures fall to the reset point.

SPDT – Switch operation is the same as the SPST with an additional contact which makes circuit when the switch operates and breaks the circuit when temperatures fall to the reset point. The manual reset limit control portion of the 89T is only available as an open on rise DPST switch. The contacts return to the closed position when the reset button is pressed after the control has cooled below the open temperature. This construction is classified as “M1 Trip Free” by UL and CSA. The manual reset control may automatically reclose at temperatures below 32°F (0°C).



When replacing a water heater thermostat, it deserves Thermo-O-Disc. Design engineers around the world have relied on Therm-O-Disc temperature sensors and controls for over 50 years. Therm-O-Disc is a recognized leader in the design and manufacture of temperature sensors and controls for the appliance, HVAC, and automotive industries