Space heating using off-peak electric heat storage

An off-peak, electric, central air heating system for buildings incorporating a heat storage material that is used to store heat generated electrically during off-peak electrical power periods and to deliver heat on demand. The heat storage material is an alkaline metal or alkaline earth metal salt such as Na2SO4, NaCl, CaCl2 and KCl individually or in combination with one another. Generation of heat during the off-peak electrical power periods is automatically controlled by an electronic time clock and time delay circuitry, and by selective variable temperature control. The heating unit is constructed with a casing having an inner jacket and an outer jacket with an air space between the two jackets. The storage material is surrounded by the inner jacket and the air space provides insulation as well as an air passage between the two jackets. The transfer of heat from the heat storage tank into the building at desired temperature is achieved by a proportional air flow control device and a two speed fan. When air is directed only through the space between the two jackets, the fan runs at low speed. When air is directed through the inner jacket containing the heat storage material, the fan runs at high speed. Also disclosed are emergency override as well as other control circuits that operate on timed as well as temperature bases to insure proper heating of the space.