this highly efficient thermic fluid heater is of vertical construction with a large diameter helical coil placed directly on top of the combustion furnace. This ensures that the intense luminous heat of the flame is fully utilized. This is the first, radiative section comprising of the first pass of hot flue gases. these gases from radiant coil are then made to pass through a second, convective heat exchanger. This is made of twin concentric helical coils, placed inside a sturdy m.s. Shell having three distinct passes of hot gases in the convective section where maximum amount of heat is extracted from the flue gases. The gases are then made to pass through the air prehater & mechanical dust collector, on way to the chimney through i.d.fan. A generously designed refractory lined external furnace is provided to ensure high furnace volume and grate area and can ensure rated output on low-grade coal and can easily burn most other fuels such as lignite, paddy husk, fire wood, bagasse, etc, without any modifications. the safety controls and instrumentations provided ensure completely safe operation and provide audio visual alarm and cuts off the combustion in case of abnormal operating conditions.