The modular design of the Vandelight gas boiler determines the following characteristics: ① Each boiler serves as a backup for the others, significantly improving equipment and investment utilization as well as operational safety. In the event of an unexpected failure of one module, the impact on heating is minimal—only 1/N (where N is the number of boilers). ② Excellent capacity expansion capability. As the heating and domestic hot water load in residential areas fluctuates (increasing or decreasing), the number of boilers can be easily adjusted to meet heating needs with relatively low investment, unlike single large boilers whose capacity is difficult to modify. Flue gas heat loss: The boiler reduces heat loss by 75% compared to traditional single-unit boilers. In conventional single steel-tube boilers, the flue gas temperature is typically maintained above 150°C to reduce low-temperature corrosion and condensation on the tail heating surfaces. In contrast, modular boilers use corrosion-resistant cast iron materials for their heating surfaces, providing strong resistance to corrosion. Through optimized heat transfer design, the flue gas temperature is reduced to below 100°C (60°C–80°C). As a result, modular boilers achieve a 75% reduction in flue gas heat loss compared to traditional single-unit boilers. Additionally, each modular boiler is equipped with a ventilation regulator. When a module is operating, its ventilation regulator opens, and when the module is not in use, the regulator closes, preventing residual heat loss from idle modules. Furthermore, the furnace wall of each modular boiler is insulated to minimize heat loss from the combustion chamber. Actual measurements show that modular boilers save approximately 1% on fuel costs compared to single-unit boilers. Gas modular boilers do not suffer from low annual thermal efficiency, load rate, or comprehensive annual energy utilization. This is because, under the controller’s coordinated operation mode, multiple boilers can be interconnected and controlled. Based on parameters such as the preset heating temperature curve, indoor temperature, and the building’s thermal inertia, the system intelligently determines the number of boilers to start or stop according to outdoor temperatures, achieving a near-unattended operation mode. During operation, the system ensures that each boiler operates at full load and high efficiency (above 91%). This effectively eliminates the common issues of low thermal efficiency, load rate, and comprehensive annual energy utilization widely seen in conventional systems, delivering significant economic and social benefits.