Bathtub heater control apparatus and method

An apparatus for bathtub heater control configured for two distinct functional operations; i.e., nominal control and safety oversight. The nominal control portion of the apparatus responds to normal operating parameters to heat the bathtub water to the desired temperature and to maintain it there within defined limits of precision. One aspect of this portion of the apparatus is proportionate temperature control. This feature employs heater power at less than full to achieve a fine degree of control at or near the desired temperature. Moreover, once the desired temperature is achieved, proportionate power of the heating element permits the maintenance of the water temperature at a more precise level. The safety oversight portion has the feature of operating only when power is applied to the heating element. This feature avoids unnecessary deactivation of the heater or heating element due to false sensing of an unsafe condition. The safety circuit preferably utilizes an internal fuse or circuit breaker requiring access to the heater itself before power can be restored to the heater. Separate temperature sensors are employed for nominal control and safety. The safety circuit requires that the temperatures sensed by these separate sensors be in agreement within a limited range.