Abstract: To solve the problem of excessive water temperature in summer, the segmented combustion technology with a generous load ratio is used to widen the load output range of the wall-hung boilers, improve their ability to adapt to different load requirements and avoid the occurrence of excessive water temperatures in summer. The key parameters of the sectional burner are determined using a combination of theoretical calculations and experimental tests, and the performance tests are completed on the installation stage. The results show that: compared to atmospheric wall-hung boilers, the minimum heat load value of the sectional burner is widened by 60% downwards to 4.0 kW without affecting the maximum heat load output, and the small fire row load output can effectively solve the problem of water temperature being too hot due to excessive load output and improve the user's comfort experience with water.

Key words: Gas-fired heating and hot water combi-boilers, Staged combustion, Load ratio, Excessive water temperature