In optimally insulated buildings (new buildings, low-energy houses, passive houses), air/water heat pumps can mostly compensate for all heat losses throughout the heating season. In such cases, when no extra heating source is required, the heat pump system is said to be in a monovalent configuration.
In case of older buildings with minimum heat insulation, the air/water heat pumps require an extra heating source when outside temperatures hit their lows during the winter. When temperature is considerably below freezing point, e.g. at -15°C, air/water heat pumps cannot deliver an adequate amount of heating power to cover the entire heating needs of such a building. As the environment temperature falls, the air/water heat pump power drops, while heating requirements of the building increase at the same time. The poorer the building insulation, the higher the heat losses. Therefore, an extra heating source must be provided for extra heating during the coldest times of the winter. To provide the extra heat required, an existing boiler, circular electrical heater, or a fireplace can be used.
Electronic controls of the AEROGOR heat pump allow regulating the bivalent system with an extra heating source. At a certain environment temperature, e.g. -10°C, the control mechanism activates the extra source to work with the heat pump in heating the building to the desired room temperature. Another option is to let only the extra source operate, without the heat pump, once the bivalent point (the point or temperature when heating with the heat pump alone is no longer sufficient) is reached. The heat pump will be reactivated when the temperature rises above the bivalent point. A third alternative is to use an excessively powerful heat pump to attain monovalent operation without an extra heating source.