The principle of operation of a condensing oil boiler is very similar to that of a gas-fired boiler. The oil is burned in the combustion chamber where the generated heat is transferred to the heating water exchanger. The design of this heat exchanger cools the exhaust gas until the condensation effect occurs. The heat from the flue gas is collected in the maximum quantity and the temperature of the flue gas is equal to the temperature of the boiler heating water. Condensing oil boilers, unlike conventional ones, are designed to operate at low temperatures, as they achieve higher efficiency. On the other hand, ordinary oil boilers have a lower temperature limit, because condensation of water from flue gases leads to boiler damage. Boilers of this type have a heating efficiency of 109%. Oil condensing boilers reduce the heating costs of the building due to their higher efficiency.