Method for controlled operation of a regeneratively heated industrial furnace with a furnace chamber, more particularly with a melting tank, more particularly for glass, having the steps: - injection of fuel into the furnace chamber via at least one fuel injector (20, 20'), which is designed for the injection of fuel, more particularly practically without combustion air, - periodically alternating directing of, on the one hand, combustion air to the furnace chamber in a first period (t 1) and, on the other hand, exhaust gas from the furnace chamber in a second period (t 2) separately from the fuel by means of a left regenerator and right regenerator assigned to the at least one fuel injector (20, 20'), which are designed for regenerative storage of heat from the exhaust gas and transfer of heat to the combustion air, whereby in a first control loop for a temperature control: - by way of a furnace chamber temperature as control variable, - a first controller (R T) for the furnace chamber temperature, and also - by way of an actuator assigned to the first controller (R T) a first adjustable actuating variable is set in the form of a fuel flow and/or of a combustion air flow, characterised in that in a second control loop for a symmetrical control relating to the left and right regenerator (50, 50'): - by way of a significant first characteristic preheat value (Q Li, T) for the heat content of the combustion air of the first regenerator and a significant second characteristic preheat value (Q Re, T) for the heat content of the combustion air of the second regenerator, whereby in each case the characteristic preheat value is given as a measure for the heat content of the combustion air, and the characteristic preheat value is formed as heat from preheated combustion air, whereby the heat from preheated combustion air is obtained from a model calculation of the regenerator (50, 50'), - a second controller (R S) for the difference of the first and second characteristic preheat value, and also - by way of an actuator assigned to the second controller (R S) a second adjustable actuating variable in the form of a heat transfer quantity influencing the heat transfer between the first and second regenerator is set, whereby the second adjustable actuating variable in the form of a heat transfer quantity influencing the heat transfer between the first and second regenerator is set in such a way that the amount of the difference between the first and second characteristic preheat value is kept below a threshold value close to zero; whereby the difference between the first and second characteristic preheat value is used as control result of the second control loop to evaluate the state of the regenerator (50, 50'), and, as heat transfer quantity, a time-span (±Δt) is set, by which the first period is extended for the hotter of the first and second regenerator and/or the first period is shortened for the colder of the first and second regenerator, and/or, as heat transfer quantity, a time-span (±Δt) is set, by which the second period is extended for the colder of the first and second regenerator and/or the second period is shortened for the hotter of the first and second regenerator. - injection of fuel into the furnace chamber via at least one fuel injector (20, 20'), which is designed for the injection of fuel, more particularly practically without combustion air, - periodically alternating directing of, on the one hand, combustion air to the furnace chamber in a first period (t 1) and, on the other hand, exhaust gas from the furnace chamber in a second period (t 2) separately from the fuel by means of a left regenerator and right regenerator assigned to the at least one fuel injector (20, 20'), which are designed for regenerative storage of heat from the exhaust gas and transfer of heat to the combustion air, whereby - by way of a furnace chamber temperature as control variable, - a first controller (R T) for the furnace chamber temperature, and also - by way of an actuator assigned to the first controller (R T) a first adjustable actuating variable is set in the form of a fuel flow and/or of a combustion air flow, characterised in that - by way of a significant first characteristic preheat value (Q Li, T) for the heat content of the combustion air of the first regenerator and a significant second characteristic preheat value (Q Re, T) for the heat content of the combustion air of the second regenerator, whereby in each case the characteristic preheat value is given as a measure for the heat content of the combustion air, and the characteristic preheat value is formed as heat from preheated combustion air, whereby the heat from preheated combustion air is obtained from a model calculation of the regenerator (50, 50'), - a second controller (R S) for the difference of the first and second characteristic preheat value, and also - by way of an actuator assigned to the second controller (R S) a second adjustable actuating variable in the form of a heat transfer quantity influencing the heat transfer between the first and second regenerator is set, whereby the second adjustable actuating variable in the form of a heat transfer quantity influencing the heat transfer between the first and second regenerator is set in such a way that the amount of the difference between the first and second characteristic preheat value is kept below a threshold value close to zero; whereby the difference between the first and second characteristic preheat value is used as control result of the second control loop to evaluate the state of the regenerator (50, 50'), and,