Lower Thermostat — Therm-O-Disc

Electric Water Heater Lower Thermostat

• 40A 120 AC
• Surface Mount
• Fits most brands of water heaters
• Adjustable temperature range: 90° F to 150° F
• Therm-O-Disc Brand

This type of thermostat is for use in 2-element water heaters, in the lower position. These water heaters often have a “non-simultaneous” design, which means that only one heating element is on at any given time. 

— Double Element Thermostat Info Page