Heating and warm water supply unit and method for operating the same

A heat exchanger is disclosed which is built up of a series of segments, which have each a fore-run and a return collector, which are interconnected by tubular or plate-shaped, substantially parallel, heat exchanging elements, in contact with cistern water through which flows the cooling medium of the heat pump. Adjacent heat exchanging segments have flow through in a reversed direction, and the fore-run and return collectors of adjacent segments are directly side by side. An electronic control unit which controls the pump and, optional valves, as a function of signals of temperature sensors on the roof surface, is included in the cistern and/or in conduits, so that during normal operation water is fed from the cistern onto the roof, is heated, and may be returned to the cistern. In times of the risk of icing of the water in the distribution pipes and on the roofing the pump and the valves are controlled in such a manner that feeding water to the roof is interrupted, and the distribution pipes, and optionally their feeding pipes, are drained off, while the pump can take care of a circulation of water in the cistern, so that the heat capacity of the water of the cistern, including at least part of the latent heat thereof, and optionally the geothermal energy fed through the cistern's wall, may be utilized.