A method for controlling and adjusting the operation of a pellet and/or biomass combustion apparatus (1; 20) of the type comprising: - a combustion chamber with a fuel charge unit operated by a fuel charge motor; - an exhaust circuit with a fan for the forced extraction of smokes, connected to said combustion chamber and operated by a fan motor; - a motorized by-pass throttle valve for recirculating part of the exhaust smokes; - a CPU, the method comprising the following steps: i) determining the temperature difference (ΔT) between the set temperature and the temperature of the air/water to be heated circulating in said combustion apparatus (1; 20); ii) determining the heating power (P t) of said apparatus (1; 20) according to said temperature difference (ΔT) and through a curve, selected among a bundle of curves, representing the power modulation coefficient (C m) and based on said temperature difference (ΔT) between the set temperature and the temperature of the air/water to be heated circulating in said combustion apparatus; iii) determining the depression (p) inside/at the level of the combustion chamber according to said heating power (P t) and through a curve which is based on the value of the heating power (P t); iv) determining the number of rpm (N f) of said fan motor for the extraction of smokes, according to said depression (p) and through a curve of the optimal depression which is included between two minimum and maximum depression curves; v) determining the value of the smoke temperature (T f) according to the heating power (P t) and through a curve of the smoke temperature (T f) based on the heating power (P t)required by said apparatus (1; 20); vi) determining the number of rpm (N c) of the motor of said fuel charge unit according to said smoke temperature (T f) and through a curve representing the fuel supply curve based on the smoke temperature (T f) inside/at the level of said combustion chamber; vii) determining the oxygen percentage (O 2 %) present in the smokes; viii) regulating the oxygen percentage (O 2 %) determined in the preceding phase, characterized in that said oxygen percentage (O 2 %) regulation phase is made by regulating the voltage value (V dc) of the motor of the by-pass valve for the recirculation in the combustion chamber of at least part of the smokes, said voltage value (V dc) being determined according to the following alternative ways: a) if the oxygen percentage value (O 2 %) in the smokes is not in excess, said voltage value (V dc) is obtained according to a curve of the by-pass valve motor voltage value (V dc) based on the difference of temperature (ΔT f) between the smoke temperature measured and the smoke temperature actually calculated; or b) if the oxygen percentage value (O 2 %) in the smokes is in excess, said voltage value (V dc) is obtained according to a curve of the voltage for the regulation of the valve motor based on the oxygen percentage (O 2 %) present in the exhaust smokes; all said phases of said method being made continuously and automatically through a feedback control made through said CPU. - a combustion chamber with a fuel charge unit operated by a fuel charge motor; - an exhaust circuit with a fan for the forced extraction of smokes, connected to said combustion chamber and operated by a fan motor; - a motorized by-pass throttle valve for recirculating part of the exhaust smokes; - a CPU, i) determining the temperature difference (ΔT) between the set temperature and the temperature of the air/water to be heated circulating in said combustion apparatus (1; 20); ii) determining the heating power (P t) of said apparatus (1; 20) according to said temperature difference (ΔT) and through a curve, selected among a bundle of curves, representing the power modulation coefficient (C m) and based on said temperature difference (ΔT) between the set temperature and the temperature of the air/water to be heated circulating in said combustion apparatus; iii) determining the depression (p) inside/at the level of the combustion chamber according to said heating power (P t) and through a curve which is based on the value of the heating power (P t); iv) determining the number of rpm (N f) of said fan motor for the extraction of smokes, according to said depression (p) and through a curve of the optimal depression which is included between two minimum and maximum depression curves; v) determining the value of the smoke temperature (T f) according to the heating power (P t) and through a curve of the smoke temperature (T f) based on the heating power (P t)required by said apparatus (1; 20); vi) determining the number of rpm (N c) of the motor of said fuel charge unit according to said smoke temperature (T f) and through a curve representing the fuel supply curve based on the smoke temperature (T f) inside/at the level of said combustion chamber; vii) determining the oxygen percentage (O 2 %) present in the smokes; viii) regulating the oxygen percentage (O 2 %) determined in the preceding phase, a) if the oxygen percentage value (O 2 %) in the smokes is not in excess, said voltage value (V dc) is obtained according to a curve of the by-pass valve motor voltage value (V dc) based on the difference of temperature (ΔT f) between the smoke temperature measured and the smoke temperature actually calculated; or b) if the oxygen percentage value (O 2 %) in the smokes is in excess, said voltage value (V dc) is obtained according to a curve of the voltage for the regulation of the valve motor based on the oxygen percentage (O 2 %) present in the exhaust smokes;