The purpose of this work is to establish the operating conditions of the boiler unit to ensure efficient combustion of nondesign Karazhyra coal. The main factors determining the efficiency of the boiler unit are the qualitative composition of the fuel being burned, the behavior of the mineral part of the fuel during combustion, the level of the fuel combustion temperature, the duration of the interaction of high temperatures on the mineral part, the properly organized method of fuel combustion and the design features of the combustion chamber. To achieve this goal, it is necessary to conduct a comprehensive study of the boiler operation using the example of burning non-design coal from the Karazhyra mine in a KV-T-116.3 -150 TEC-1 boiler in Semey. As a result of the conducted research, qualitative parameters of operation in real conditions of the boiler unit during the combustion of non-design Karazhyra coal with variable heat output were obtained. The analysis of the data obtained during the combustion of non-design coals will allow us to further develop a number of practical recommendations for optimizing the operation of cleaning agents installed on the boiler.