Multi-boiler and control method thereof for preventing back flow of exhaust gas

A control method of preventing backflow of exhaust gas of a multiboiler comprising a plurality of boilers arranged in line, each of the plurality of boilers including a fan, a sensor measuring revolutions per minute (RPM) of the fan of each of the plurality of boilers and a controller controlling the RPM of the fan of each of the plurality of boilers on a basis of the RPM measured by the sensor, wherein any one of the controllers of the plurality of boilers is set as a master controller and the other controllers of the plurality of boilers are set as slave controllers, the master controller and the slave controllers being connected by a communication line to communicate with each other, the control method comprising:

• measuring the RPM of the fan of each of the plurality of boilers by the controller of each of the plurality of boilers that are in operation;
• calculating an average RPM of the fans of the plurality of boilers that are in operation based on the measured RPM by using the master controller;
• determining the RPM of the fan of each of the plurality of boilers that are not in operation on a basis of the average RPM by using the master controller;
• and
• operating the fan of each of the plurality of boilers that is not in operation on a basis of the determined RPM by using the master controller.