Hot water heater systems and methods for controlling electronic mixing valves

1. A method of 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:

monitoring an input temperature of water supplied to the valve from a cold water supply;

storing a minimum of the input temperature;

looking up a predefined position limit associated with the stored minimum in a lookup table;

setting a position limit of the valve to the predefined position limit;

and

operating the valve within a range constrained by the position limit of the valve;

wherein the position limit of the valve is greater than a fully closed position of the valve and less than a fully open position of the valve.

2. The method of claim 1 , wherein the stored extremum is a daily extremum.

3. The method of claim 1 , wherein the step of storing an extremum of the input temperature further comprises storing the extremum within a moving seven-day window.

4. The method of claim 1 , wherein the predefined position limit is a minimum open position, and the step of looking up a predefined position limit comprises looking up a predefined minimum open position associated with the stored minimum temperature in a lookup table, and setting the minimum open position of the valve to the predefined minimum open position.

5. A method of 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:

monitoring an input temperature of cold water supplied to the valve;

storing a value of the input temperature;

looking up a predefined position limit associated with the stored value in a lookup table;

setting a position limit of the valve to the predefined position limit;

and

operating the valve within a range constrained by the position limit of the valve.

6. The method of claim 5 , wherein the position limit of the valve is a minimum open position.

7. The method of claim 5 , wherein the stored value is a daily minimum temperature.

8. The method of claim 5 , wherein the stored value is a daily maximum temperature.

9. The method of claim 5 , wherein the stored value is a daily average temperature.

10. A hot water heater, comprising:

a cold water supply;

a hot water tank;

an electronic mixing valve, the valve connected to the cold water supply, the hot water tank, and a mixed output line, the valve operable to receive variable input from each of the cold water supply and the hot water tank and to provide a mixed output flow of water in the mixed output line;

a motor in communication with the valve, the motor operable to move the valve between a fully open position and a fully closed position;

a temperature sensor operable to sense the temperature in one of the cold water supply and the hot water tank; and

a controller in operative communication with the temperature sensor and the motor, the controller operable to monitor the sensed temperature, store an extremum of the sensed temperature, look up a predefined position limit associated with the stored extremum in a lookup table, set a position limit of the valve to the predefined position limit, and operate the motor to move the valve within a range constrained by the position limit of the valve, wherein the position limit of the valve is greater than the fully closed position of the valve and less than the fully open position of the valve.

11. The hot water heater of claim 10 , wherein the temperature sensor is operable to sense the temperature in the cold water supply, and the controller is operable to store a minimum of the sensed temperature and set a position limit of the valve based on the stored minimum by looking up a predefined minimum open position associated with the stored minimum temperature in a lookup table, and setting the minimum open position of the valve to the predefined minimum open position.

12. The hot water heater of claim 10 , wherein the temperature sensor is operable to sense the temperature in the hot water tank, and the controller is operable to store a maximum of the sensed temperature and set a position limit of the valve based on the stored maximum by looking up a predefined maximum open position associated with the stored maximum temperature in a lookup table, and setting the maximum open position of the valve to the predefined maximum open position.