The present invention, in the regenerative boiler having an external pump known in particular, relates to a regenerative boiler having an external pump, connected to the heating supply pipe outlet of the hot heat exchanger to the heat storage tank heating water supply pipe that gongjeop with the inlet of the built-in pump to have a form which is circulated through the hot water mode is selected, the main heat exchanger heated number 3 bangbyeon and heating supply pipe, a thermal storage tank heating water supply pipe and the internal pump of the hot water heat exchanger is discharged from, and respectively connected to the inlet and outlet of the heating pipe the heating supply pipe and heating poems by the end of the restitution tube connected directly to the respective storage tank selected heating mode external pump cycling by supplying a number of heating stored in the storage tank directly into the heating pipe and built-in pump is not heating in the storage tank main heat continue cycling groups and but so as to continuously heated, and install the main heating outlet and heating water supply and heating water-exchange tubes are respectively the hot water temperature sensor and heating supply temperature sensor and heating return temperature sensor of the heat exchanger, corresponds to a result by comparing the temperature difference (ΔT _sET) is set as a temperature difference (T1-T2 = ΔTmea) is measured through the heating supply temperature sensor and the heating return temperature sensor causes the control cross to the flow rate through an external pump and in that automatically controlled.
Therefore, it is possible to prevent energy waste and noise generated when using hot water resulting from the external pump is idle, in particular, to a more economical and effective heating.