CASCADE SYSTEM AND CONTROL METHOD OF THE CASCADE SYSTEM AND A HEATING BOILER COMPRISING THE CASCADE SYSTEM

摘要

An object of the present invention is to provide a cascade system having a simple structure, a method of controlling same, and a heating-dedicated boiler constituting the cascade system. When a portion of boilers constituting a multi boiler is selectively operated according to a heating load, the cascade system sufficiently supplies hot water from the boilers to the heating load. To this end, a cascade system according to the present invention includes: a boiler pump that is selectively operated according to a heating load, and circulates heating water; a plurality of boilers including a heat exchanger that transfers combustion heat from a burner to the heating water circulated by the boiler pump; and a heating load pump circulating the heating water. The boilers include: a three way valve whereby a passage through which the heating water circulated by the boiler pump and the heating load pump is recovered along a heating water recovering pipe is selectively directed toward either an inlet of the heat exchanger or a heating water supply pipe connected to an outlet of the heat exchanger; and a control part controlling a direction of the three way valve according to the heating load.