Combustion device

A combustion system, comprising a plurality of combustion devices, each of which comprises:

• a combustion unit;
• an ignition means;
• a fuel supply unit for supplying fuel to the combustion unit;
• a blower unit for supplying air for combustion;
• an exhaust port that discharges combustion exhaust;
• a control means that, before ignition of fuel supplied to the combustion unit by operation of the ignition means, performs air purge of the combustion unit at a predetermined air blowing amount by driving the blower unit;
• and
• a setting means for setting to indicate that a check valve for preventing back flow of exhaust is connected to the exhaust port;
• wherein, when the setting means is set to indicate that the check valve is connected, the control means controls an operation of the blower unit so that slow-start air purge is performed in which a time interval from a start of air purge until the predetermined air blowing amount is reached becomes longer, than in a case in which no such check valve is connected, and
• respective exhaust ports of the plurality of combustion devices are connected to a common exhaust duct, and respective check valves are disposed between the common exhaust duct and respective exhaust ports.