A calorifier is basically a heating fan with a coil and functions like a heat exchanger. In a calorifier, air is heated indirectly by circulating over the heating coil. Heat will merely be thermally transferred. The function of a calorifier is to retain thermal energy for later use and supplement primary heat source during peak hours. Calorifiers are commonly seen in hospital and factory application, where excess steam can be used to heat the water but calorifiers can also be used in commercial or even small domestic dwellings applications.