Abstract: A fully-enclosed condensed water recovery unit with self-suction and filtering capabilities and controlled by PLC program is developed. When the oil tank begins to be heated, the valve of original condensed water pipe network and the drainage outlet of the condensed water recovery unit are opened, and the drainer at the condensate water drain outlet of oil tank is closed. When there is clean condensed water discharged from the drainage outlet, the inlet of the unit is opened, and the drainage outlet is closed; meanwhile, the unit is adjusted to PLC mode, and then it can run automatically. A filter is installed at the outlet of the unit to ensure the filtered water meet the requirements of boiler water. All circulation cylinder, storage cylinder and condensed water pipes are insulated to preserve the heat of condensed water. The unit is prospective for wide application.