A BUILDING VENTILATION AIR-TO-AIR HEAT EXCHANGER CONTROL

摘要

In heat exchangers for buildings certain atmospheric conditions cause condensation and freezing of the humidity in the exhaust air, thereby preventing heat exchanging action. Prior art remedies are to switch off or to supply heat from a heat source. Such solutions are not energy- efficient. Other remedies feed back a portion of the outside air that has just passed through the heat exchanger into the cold outside air at a feeding point upstream of the heat exchanger. According to the invention, the beginning of condensation and ice build-up is determined by a change in the pressure drop across the heat exchanger, said change opening a damper to permit a part of the heated outside air to return to the input end of the heat exchanger.