Abstract: A heat accumulator (18) arranged in heat exchange relation with a heating system. The accumulator comprises a body of a material having a high heat capacitivity and a high melting point, for instance cast iron, ceramics material. The accumulator is arranged for being heated by electric energy (19) to a temperature considerably higher than the maximum temperature of the heating system. A conduit (22) containing heat transporting fluid in a liquid phase is arranged for communication with the water system for settling the heat accumulator in heat exchange relation with the water system of the heating system. In a preferred embodiment the conduit (22) is an open conduit in direct communication with the water system.

Abstract: A heat accumulator is disposed in heat exchange relationship with a heating system. The accumulator includes a body of a material having a high heat capacity and a high melting point, such as iron or ceramic material. The accumulator is arranged for being heated by electrical energy during non-peak hours, or "night" energy, to a temperature much higher than the maximum temperature of the heating system. A conduit containing a fluid in a liquid phase is arranged for communication with the water system for setting the heat accumulator in heat exchange relation with the water system of the heating system. A pump is used on startup at high speed to expel water vapor from the accumulator quickly, with the pump having a reduced speed for ordinary operation following startup. The higher pump speed and low conduit volume in the heat accumulator prevents flashing of the water into water vapor during startup operation.