Control apparatus and method for electric heater with external heat source

In combination:

• a water heater including a water storage tank, an electrically resistive heating element located in the tank, and a tank-mounted thermostat which closes in response to a demand for water heating to allow electric current to flow to the heating element and which opens when the demand for water heating has been satisfied to interrupt the electric current flow to the heating element;
• an external heat source including means for circulating water between the tank and the external heat source, whereby water is heated by the external heat source and returned to the tank;
• and
• apparatus for controlling the water heater and external heat source, said apparatus comprising:
• electric current sensing means for sensing electric current flow to the heating element and for providing a first electrical signal indicative thereof;
• temperature sensing means external to the tank for sensing temperature of the water at a selected location external to the tank and for providing a second electrical signal indicative thereof;
• and
• control means for coordinately controlling the heating element and the external heat source, said control means being adapted to interrupt the electric current flow to the heating element to deactivate the heating element and to activate the external heat source to heat water circulated between the tank and the external heat source in response to said first electrical signal, said control means being adapted to deactivate the external heat source in response to said second electrical signal indicating that the water temperature at said selected location has exceeded a predetermined temperature.

A method of controlling a water heater and an external heat source operatively connected with the water heater, the water heater including a water storage tank, an electrically resistive heating element located in the tank, and a tank-mounted thermostat which closes in response to a demand for water heating to allow electric current to flow to a heating element and which opens when the demand for water heating has been satisfied to interrupt the electric current flow to the heating element, the external heat source including means for circulating water between the tank and the external heat source, whereby water is heated by the external heat source and returned to the tank, said method comprising the steps of:

• sensing the electric current flow to the heating element and providing a first electrical signal indicative thereof;
• sensing the temperature of the water at a selected location external to the tank and providing a second electrical signal indicative thereof;
• interrupting the electric current flow to the heating element to deactivate the heating element and activating the external heat source in response to said first electrical signal, water circulated between the tank and external heat source being heated by external heat source;
• and
• deactivating the external heat source in response to said second electrical signal indicating that the water temperature has exceeded a predetermined temperature.

A method of heating water, comprising the steps of:

• providing a water storage tank, an electrically resistive heating element located in the tank, and a tank-mounted thermostat which closes in response to a demand for water heating to allow electric current to flow to the heating element and which opens when the demand for water heating has been satisfied to interrupt the electric current flow to the heating element;
• providing an external heat source;
• sensing the electric current flow to the heating element in response to the closure of the thermostat and providing a first electrical signal indicative thereof;
• interrupting the electric current flow to the heating element in response to said first electrical signal to deactivate the heating element;
• activating the external heat source in response to said first electrical signal;
• circulating water between the tank and the external heat source, whereby water is heated by the external heat source and returned to the tank;
• sensing the temperature of the water at a selected location external to the tank and providing a second electrical signal indicative thereof;
• and
• deactivating the external heat source in response to said second electrical signal indicating that the water temperature has exceeded a predetermined temperature.