Hot water heater systems and methods for controlling electronic mixing valves

1. A method for controlling an electronic mixing valve for a hot water heater, the electronic mixing valve providing a flow of water in a mixed output line, the method comprising:

determining a temperature value inside a hot water tank of the hot water heater;

comparing the hot water tank temperature value to a setpoint temperature value; and

comparing a temperature value for water in the mixed output line to a lower setpoint threshold value when the hot water tank temperature value is greater than the setpoint temperature value, wherein the lower setpoint threshold value is less than the setpoint temperature; and

setting the electronic mixing valve to a safe position wherein the electronic mixing valve is less than fully open when the temperature value for water in the mixed output line is less than the lower setpoint threshold value.

2. The method of claim 1 , wherein the safe position is a first safe position, and further comprising:

comparing the temperature value for water in the mixed output line to an upper setpoint threshold value when the hot water tank temperature value is greater than the setpoint temperature value, wherein the upper setpoint threshold value is greater than the setpoint temperature; and

setting the electronic mixing valve to a second safe position wherein the electronic mixing valve is less than fully open when the temperature value for water in the mixed output line is greater than the upper setpoint threshold value.

3. The method of claim 2 , wherein comparing the temperature value for water in the mixed output line to the upper setpoint threshold value occurs when the temperature value for water in the mixed output line is greater than the lower setpoint threshold value.

4. The method of claim 2 , wherein the second safe position is less open than the first safe position.

5. The method of claim 1 , further comprising determining whether a temperature of the water in the mixed output line requires adjustment, and

wherein determining the temperature value inside the hot water tank occurs when the temperature of the water in the mixed output line requires adjustment.

6. The method of claim 5 , wherein determining whether the temperature of the water in the mixed output line requires adjustment comprises comparing a temperature error value to a temperature tolerance, and wherein the temperature of the water in the mixed output line requires adjustment when the temperature error value is greater than the temperature tolerance.

7. The method of claim 6 , further comprising:

determining the temperature value for water in the mixed output line; and

comparing the temperature value for water in the mixed output line to the setpoint temperature to determine the temperature error value.

8. A method for controlling an electronic mixing valve for a hot water heater, the electronic mixing valve providing a flow of water in a mixed output line, the method comprising:

determining a temperature value inside a hot water tank of the hot water heater;

comparing the hot water tank temperature value to a setpoint temperature value; and

comparing a temperature value for water in the mixed output line to an upper setpoint threshold value when the hot water tank temperature value is greater than the setpoint temperature value, wherein the upper setpoint threshold value is greater than the setpoint temperature; and

setting the electronic mixing valve to a safe position wherein the electronic mixing valve is less than fully open when the temperature value for water in the mixed output line is greater than the upper setpoint threshold value.

9. The method of claim 8 , further comprising determining whether a temperature of the water in the mixed output line requires adjustment, and

wherein determining the temperature value inside the tank of the hot water heater occurs when the temperature of the water in the mixed output line requires adjustment.

10. A hot water heater system, comprising:

a hot water tank having a cold water inlet line and a hot water outlet line;

an electronic mixing valve fluid coupled to the cold water inlet line and the hot water outlet line;

a mixed output line fluidly coupled to the electronic mixing valve; and

a controller operatively coupled to the electronically controlled mixing valve and operable to:

determine a temperature value inside the hot water tank;

compare the hot water tank temperature value to a setpoint temperature value; and

compare a temperature value for water in the mixed output line to a lower setpoint threshold value when the hot water tank temperature value is greater than the setpoint temperature value, wherein the lower setpoint threshold value is less than the setpoint temperature; and

set the electronic mixing valve to a safe position wherein the electronic mixing valve is less than fully open when the temperature value for water in the mixed output line is less than the lower setpoint threshold value.

11. The hot water heater system of claim 10 , wherein the safe position is a first safe position, and wherein the controller is further operable to:

compare the temperature value for water in the mixed output line to an upper setpoint threshold value when the hot water tank temperature value is greater than the setpoint temperature value, wherein the upper setpoint threshold value is greater than the setpoint temperature; and

set the electronic mixing valve to a second safe position wherein the electronic mixing valve is less than fully open when the temperature value for water in the mixed output line is greater than the upper setpoint threshold value.

12. The hot water heater system of claim 11 , wherein comparing the temperature value for water in the mixed output line to the upper setpoint threshold value occurs when the temperature value for water in the mixed output line is greater than the lower setpoint threshold value.

13. The hot water heater system of claim 11 , wherein the second safe position is less open than the first safe position.

14. The hot water heater system of claim 10 , wherein the controller is further operable to determine whether a temperature of the water in the mixed output line requires adjustment, and

wherein determining the temperature value inside the hot water tank of the hot water heater occurs when the temperature of the water in the mixed output line requires adjustment.

15. The hot water heater system of claim 14 , wherein determining whether the temperature of the water in the mixed output line requires adjustment comprises comparing a temperature error value to a temperature tolerance, and wherein the temperature of the water in the mixed output line requires adjustment when the temperature error value is greater than the temperature tolerance.

16. The hot water heater system of claim 15 , wherein the controller is further operable to:

determine the temperature value for water in the mixed output line; and

compare the temperature value for water in the mixed output line to the setpoint temperature to determine the temperature error value.

17. The hot water heater system of claim 10 , further comprising a temperature sensor operatively coupled to the mixed output line and the controller, and wherein the temperature value for water in the mixed output line is determined based on signals received from the temperature sensor.

18. The hot water heater system of claim 17 , wherein the temperature sensor is a thermistor.

19. The hot water heater system of claim 10 , further comprising a temperature sensor operatively coupled to the hot water tank and the controller, and wherein the hot water tank temperature value is determined based on signals received from the temperature sensor.

20. The hot water heater system of claim 19 , wherein the temperature sensor is a thermistor.