I am using this control to control my boilermate hot water maker. This control monitors the hot water temperature in the boilermate. When the water temperature drops to 110 degrees, the control turns on the circulator. The circulator pumps hot boiler water through the boilermate heating loop, which heats the surrounding water in the boilermate. When the high limit is reached, the control turns the circulator off. The cycle repeats when the water temperature drops to the low limit set point.