Abstract: A system and method are provided for controlling water temperature in a body of water. The temperature control system includes a processor, a user interface for receiving a desired temperature and a desired time for reaching the desired temperature, a sensor interface for receiving sensor information from one or more sensors, and an actuator interface for controlling a plurality of heat sources. The processor determines one or more optimal heat sources for heating the body of water to the desired temperature by the desired time. The processor controls the one or more optimal heat sources through the actuator interface and periodically polls the sensor interface to determine whether changes in the operating environment require additional or alternate heat sources to be activated to ensure that the body of water is heated to the desired temperature by the desired time.

Abstract: A thermally responsive electrical control device is operable for producing a control signal having first and second voltage levels for controlling the operation of a system actuating device for first and second modes of operation. One embodiment of the device includes a multiple bridge circuit for sensing two temperatures and for making multiple control decisions in response to the two temperatures. Another embodiment of the device includes a thermistor and a nonlinear variable resistance element which is matched in a substantially linear relation with the thermistor for compensating for the inherent substantially nonlinear character of the thermistor. Still another embodiment of the device includes a monitoring circuit which is interconnected to a bridge circuit of the device for providing visual indications of sensed temperatures without significantly interrupting the control function of the device.