Hot water boiler or hot water system is a heating system that uses water or oil as the heat transfer medium to provide warmth to homes, buildings, or industrial processes. These systems work by heating the water or oil in a tank or reservoir and then circulating it through pipes or ducts to provide heat to various points of use. industrial hot water boiler is a device that uses fuel or electricity to heat water and produce hot water for industrial processes and applications. The working principle of a hot water boiler involves the transfer of heat energy from the fuel or electricity source to the water, which is then circulated through a piping system to the application.