Sediment buildup warning device for water heaters

Claim 1

In a water storage tank adapted to contain water to be heated and having a shell closed at the lower end by a bottom head joined to the shell, a gas heating unit located adjacent the bottom head of the tank to heat said water, at least one flue secured to the bottom head above the gas heating unit and extending upwardly within the tank for discharge of flue gases, a first temperature sensor for controlling normal operation of the heating unit a temperature sensing warning device in contact with the wall of the tank located below said first sensor and from one to four inches above the joint between the lower head and shell with said device being disposed to sense the increase in temperature in the tank wall above the normal operating temperature as the result of buildup of insulating sediment on the bottom head of the storage tank preventing the passage of heat from the heating unit through the bottom head to the water contained in the tank, a safety shut down warning means associated with the temperature sensing device, and switching means electrically connected to the temperature sensing device and to the safety shut down warning means to actuate the latter when the switching means is operated by the temperature sensing device when the latter senses temperature in the tank wall which is above normal.