Robertshaw ST12-80 ST1205113 Surface Mounted Hot Water Thermostat also known as ST12-80K replaces W1M2/80

60C-80C Thermostat Surface Mounted for controlling a single hot water element


Also known as ST1205113. Sometimes this thermostat will have a yellow knob instead of pink. The green knob version controls 50C-70C. Used in many of the popular electric hot water services such as Rheem, Dux, Rinnai just to name a few.


  • Controls element to heat water between 60C to 80C
  • 4-terminals to save wiring confusion – 2 terminals to element and one each for active and neutral – wiring diagram included
  • Has safety over temperature cut out at 84C so that water doesn’t boil in the event the thermostat fails
  • Rated to 30 Amps so can control up to 6KW on a 240Volt electrical line
  • Can be used with 5-terminal thermostats to control a second element in the tank
  • Surface mounted means it senses the heat on the side of the tank so no need for an internal probe