Water heater having improved temperature control

Abstract

A water heating system for a water heater includes a water tank and a heating element heating the water in the tank. A temperature controller has a temperature sensor and a temperature setting device that controls water temperature responsive to a user set temperature. A demand controller controls the temperature controller to override the set temperature responsive to demand for heated water. Demand is determined by water use measured by water flow. During non-demand periods the heating element can be turned off.

1 . A water heating system, comprising:
 a water tank having a volume;   a heating element adapted to heat the water in the tank and having a heating rate;   a temperature controller having a temperature sensor and a temperature setting device adapted to control water temperature responsive to a user set temperature; and   a demand controller adapted to control the temperature controller responsive to demand for heated water, the demand controller comprising:   a water flow sensor adapted to sense an amount of water flow through the tank;   an intake temperature sensor adapted to measure the intake water temperature;   a current temperature sensor adapted to sense a current water temperature;   a set temperature memory adapted to store the user set temperature;   a intake temperature memory adapted to store the intake water temperature;   a demand table memory adapted to store the water flow information for periods of time over the recurring period comprising periods during a day and days of a week;   a current temperature memory adapted to store the current water temperature;   a processor adapted to store the user set temperature when set by the user, adapted to periodically read and store the water intake temperature; adapted to read water flow sensed by the water flow sensor to store and update water demand information for the water flow over a recurring period of time adapted to periodically read and store the current water temperature, adapted to determine when the current time is within the demand period and to allow the temperature controller to control water temperature to the user set temperature during the demand period, adapted to determine when the current time is within a non-demand period to disable the temperature controller during the non-demand, adapted to determine when water heating is to start during the non-demand period to raise the current water temperature to the user set temperature at the start of a next demand period responsive to the current water temperature, the user set temperature, the volume and the heating rate.   
     
     
         2 . A water heating system, comprising:
 a water tank having a volume;   a heating element adapted to heat the water in the tank and having a heating rate;   a temperature controller having a temperature sensor and a temperature setting device adapted to control water temperature responsive to a user set temperature; and   a demand controller adapted to control the temperature controller responsive to demand for heated water.   
     
     
         3 . A system as recited in  claim 2 , wherein the demand is determined by a user setting of on/off heating periods. 
     
     
         4 . A system as recited in  claim 2 , wherein the demand is determined by water flow. 
     
     
         5 . A system as recited in  claim 4 , wherein demand periods of the demand are periods of a day and days of a week. 
     
     
         6 . A system as recited in  claim 5 , wherein the demand periods comprise periods when flow is above a threshold. 
     
     
         7 . A system as recited in  claim 6 , wherein periods of demand change over time based on changes in water flow. 
     
     
         8 . A system as recited in  claim 2 , wherein demand periods of the demand are determined by water temperature. 
     
     
         9 . As system as recited in  claim 7 , wherein the demand periods comprise periods when water temperature is below a threshold. 
     
     
         10 . As system as recited in  claim 2 , wherein the demand controller starts temperature recovery to the set temperature in a non-demand period before a demand period. 
     
     
         11 . A water temperature control method for a water heater, comprising:
 setting a set temperature for water temperature of water in the water heater;   determining demand periods and non-demand periods for use of hot water; and   overriding the set temperature during non-demand periods.