Patent ID: 7985943

Claim:
A backup water heater for installation downstream of a water outlet of a thermosiphon solar water heater, comprising: a corrosion resistant tank; a burner, and a gas feed valve system including at least one electrovalve connected to a cast body configured to deliver a gas to said burner; a bimetallic temperature detector disposed to detect water temperature within said tank; a flow detector activated by water flow through said tank; a first spark plug positioned to ignite said burner, and a second spark plug positioned to detect current changes generated by ionization effect caused by the flame after said burner is ignited; an electronic controller in operative communication with said electrovalve, said temperature detector, said flow detector, and said first and second spark plugs to send a current to said first spark plug upon detection of a low setpoint temperature from said temperature detector and a detected setpoint flow from said flow detector, said electronic controller causing gradual opening of said electrovalve to supply gas to said burner to ignite said burner with said first spark plug; said electronic controller configured to detect the change of current from said second spark plug and to generate a visual display of normal operation, or to close said electrovalve and terminate operation of said water heater if the change of current is not detected within a defined time and to generate a visual display of equipment error.