Electric Water Heater Controls

Snap-Action Bimetal Discs in Both Controls

The 59T and 66T series Bimetal Thermostat Temperature Controls are designed to meet the high electrical capacity requirements of

electric water heaters. Both use a temperature sensitive bimetal disc to deliver snap-action to the

contacts. The speed and force of contact separation provides long-dependable control life at high

electrical loads.

Thermal Response of the 59T and 66T

The bimetal discs of the 59T and 66T are in intimate thermal contact with the backplates of the

controls. Properly mounted, the 59T and 66T series controls provide good thermal response on

storage tank water heaters.

Switch Actions

The 59T is available in two switch actions:

Automatic reset SPST – The switch opens the normally closed contacts on temperature rise. The

contacts automatically return to the closed position when temperatures return to the reset point.

Automatic reset SPDT – This operation is the same as the SPST with the addition of an auxiliary

set of contacts, which make circuit upon opening of the normally closed contacts and breaks this

circuit upon automatic reset.

The 66T is a manual reset DPST – The switch opens two sets of normally closed contacts on temperature rise to provide full power disconnect of both conductors. The contacts will reset to the closed

position when the reset button is depressed before the control has cooled to 90°F. Once opened,

until the reset button is pressed, the contacts will not automatically reset at control temperatures

above 32°F (0°C).

The construction is classified as “M2 Trip Free” by the approval agencies. This patent pending

design holds the contacts open in the event the reset button is held in the depressed position in

an attempt to defeat the manual reset function of the thermostat.