Patent ID: 7055760

Claim:
A temperature control apparatus for a liquid heater having two fittings for connecting liquid conduits to the heater, one of the fittings being either an inlet or an outlet For liquid, another of the fittings being another of the inlet or the outlet for the liquid, the heater having a first temperature sensor adjacent to said one fitting and a second temperature sensor adjacent to said another fitting, the apparatus including a memory having values for a first temperature value, where the heater stops heating, a second temperature value lower than the first value, and a third temperature value higher than the first value, where the heater is shut off, both sensors being capable of sensing the first temperature value and the second temperature value and at least one of the sensors also sensing the third temperature value, and controls which compare temperature readings from each of the sensors wit each of the first temperature value, the second temperature value and the third temperature value, the heater having an overheat condition when a temperature exceeds the third temperature value, a high condition when a temperature exceeds the first temperature value, a normal condition when a temperature is between the second temperature value and the first temperature value and a low condition when a temperature is less than the second temperature value, the apparatus indicating the overheat condition when one of the sensors indicates a temperature exceeding the third temperature value, the high condition when either sensor indicates a temperature exceeding the first temperature value, but neither sensor indicates a temperature exceeding the third temperature value, a normal condition when either sensor indicates a temperature exceeding the second temperature value, but neither sensor indicates a temperature exceeding the third temperature value, and a low condition when both sensors indicate temperatures less than the second temperature value.