Electrical heater for heating liquid

Claim 1

An electrical heater for heating a liquid, the heater comprising: a pair of conductors for applying electrical energy to the heater; an electrical heating element coupled across said conductors; a temperature-sensitive device coupled between said heating element and one of said conductors for feeding of current to said heating element to control the operating temperature of said element as a function of ambient temperature; a tubular enclosure sealed against ingress of water and formed by a metal tube closed against ingress of water at one end, an electrically insulative plastics tube joined at one of its ends in water-tight manner to the other end of said metal tube, and a sealing plug through which said conductors extend and which seals the other of the ends of said plastics tube, said heating element being within said metal tube and said temperature-sensitive device being within said plastics tube; electrical insulating means electrically insulating said heating element from said metal tube; and a glass tube containing said tubular enclosure and which is closed against ingress of moisture at one end and is sealed against ingress of water at its other end by sealing means through which said conductors pass.