Abstract: A system including temperature measuring devices, a controller, and an actuator, maintains a desired gas temperature range in the secondary combustor by proportionally making adjustments to the primary air orifice or other primary air valve of a cordwood burning appliance. Heat output of the appliance is directly related to the temperature of the gases in the secondary combustor, and sufficient engagement of the second combustor during off-gassing of volatiles from the wood will control emissions from the appliance. The operator can select a desired room temperature via the thermostat and the controller will use different secondary gas temperature target ranges in order to meet the desired room temperature as commanded by the thermostat throughout the burn event. The controller also controls the start-up phase of combustion and charcoal phase of combustion.