System and method for controlling a water heater

A controller for a water heating system having a heater, an outlet conduit for supplying heated water to a plurality of users, and an inlet conduit for introducing unheated water through an inlet orifice to replenish heated water supplied to said users, the controller comprising:

• an outlet sensor for measuring an outlet temperature of said heated water and generating an outlet temperature signal representative thereof;
• an inlet sensor for measuring an inlet temperature of said unheated water and generating an outlet temperature signal representative thereof at a location adjacent the inlet orifice and having a reference temperature value when unheated water has not been introduced for a preselected period of time and a dynamic, reduced temperature value when unheated water has been introduced within said preselected period;
• logic responsive to said inlet temperature signal to derive a control temperature value representative of the difference between said reference temperature value and said reduced temperature over said preselected period;
• and
• control circuitry responsive to said outlet temperature signal for controlling the heater to maintain a preselected relationship between the outlet temperature and said control temperature value.

A method for controlling a water heating system having a heater, an outlet conduit for supplying heated water to a plurality of users, and an inlet conduit for introducing unheated water through an inlet orifice to replenish heated water supplied to said users, the method comprising the steps of:

• measuring an outlet temperature of said heated water and generating an outlet temperature signal representative thereof;
• measuring an inlet temperature of said unheated water and generating an inlet temperature signal representative thereof, said inlet temperature being measured at a location adjacent the inlet orifice such that said inlet temperature drops when unheated water is introduced;
• deriving, in response to said measured inlet temperature signal, a control temperature value representative of the amount by which said inlet temperature drops;
• and
• controlling the heater in response to said outlet temperature signal to maintain a preselected relationship between said outlet temperature and said control temperature value.

A method for controlling a water heating system having a heater, an outlet conduit for supplying heated water to a plurality of users, and an inlet conduit for introducing unheated water through an inlet orifice to replenish heated water supplied to said users, the method comprising the steps of:

• measuring an outlet temperature of said heated water and generating an outlet temperature signal representative thereof;
• measuring an inlet temperature of said unheated water and generating an inlet temperature signal representative thereof, said inlet temperature being measured at a location adjacent the inlet orifice, and having a reference temperature value when unheated water has not been introduced for a preselected period of time and a dynamic, reduced temperature value when unheated water has been introduced within said preselected period;
• deriving, in response to said measured inlet temperature signal, a control temperature value representative of the difference between said reference temperature value and said reduced temperature over said preselected period;
• and
• controlling the heater in response to said outlet temperature signal to maintain a preselected relationship between the outlet temperature and said control temperature value.