Applies to electric water heaters intended for electrical operation by direct or alternating current at low or medium voltages, including storage and instantaneous water heaters, wash boilers, instantaneous bath heaters and similar appliances and electric urns having a capacity of 1 gallon or more. The appropriate requirements of this specification apply to water heaters where the electrical heating medium is complementary to another form of energy. It does not apply to electric steam generators, electric sterilisers, electric water heaters specially designed for industrial application, electric washing machines, electric kettles or electric jugs.