Abstract: An embodiment of a spa control system includes a heater, a pump for circulating water through the pump, one or more sensors for monitoring temperature, and an electronic controller coupled to the heater, pump and sensor(s) for controlling the heater and pump based on the rate of change in temperature at the sensor(s). A method of controlling a heater in a spa with a spa control system is also disclosed.

Abstract: A spa control system that measures the flow of water through the heater and accurately reports water temperature in the spa using only one solid-state sensor in the heater. The rate of flow is determined by energizing the pump, with the heater still de-energized, and observing the rate in which the moving water cools the inside of the heater. If there is no circulation of water through the heater, the temperature of the sensor will continue to rise from the energy applied when the heater was briefly energized. This rise will be quite significant and a clear indication of a flow problem. If the flow is found to be adequate, the heater will be energized for a normal period of time. The sensor is now carefully monitored for a sudden increase in temperature, which would indicate loss of a normal flow of water.