Are fully premixed wall-mounted boilers really efficient and energy-saving?

As living standards improve, people are placing increasing emphasis on the comfort of their home environments. Wall-mounted boilers meet both household heating and domestic hot water needs, and their dual-purpose feature—serving two functions with a single unit—is highly popular.
When choosing a wall-mounted boiler, “energy efficiency” is an important factor to consider. So, let’s take a closer look at whether fully premixed wall-mounted boilers are truly efficient and energy-saving! Fully premixed wall-mounted boilers mainly incorporate two key technologies: full-mix combustion technology and condensation technology. What’s the difference between conventional combustion and fully premixed wall-mounted boiler combustion? In conventional combustion, the load is adjusted by regulating the opening of a gas proportioning valve. In this process, while the amount of gas can be adjusted, the intake air volume cannot be modified. Since the gas-to-air ratio doesn’t reach the optimal mixing ratio for complete combustion, this combustion technology has very low thermal efficiency. In contrast, fully premixed wall-mounted boiler combustion involves thoroughly mixing air and gas before ignition. Fully premixed wall-mounted boilers feature rapid combustion speed, high flame temperature, complete combustion, a small excess air coefficient, and high thermal efficiency. Why are fully premixed wall-mounted boilers energy-efficient? The fully premixed combustion method ensures that the amount of air required for gas combustion is precisely matched to achieve more complete combustion. If there’s insufficient air, combustion won’t be fully effective. Unlike conventional wall-mounted boilers, fully premixed boilers maintain an optimal air-to-gas ratio under all load conditions, ensuring complete combustion without any excess air. This results in more efficient combustion and greater energy savings. Another key factor contributing to their energy efficiency is condensation. Fully premixed wall-mounted boilers reduce flue gas temperature, causing the water vapor in the exhaust gases to condense. As a result, nearly all the sensible heat and part of the latent heat from the water vapor are effectively utilized, significantly improving the overall efficiency of the system. In contrast, conventional boilers operate at much higher flue gas temperatures, so the latent heat contained in the water vapor remains largely untapped.
Meanwhile, the high flue gas temperature carries away sensible heat, reducing thermal efficiency. Fully mixed furnaces are more energy-efficient than conventional wall-mounted boilers. A mature wall-mounted boiler technology features an adaptive system based on oxygen sensors. However, oxygen sensors can become poisoned over time, leading to a gradual decrease in their detection sensitivity after prolonged use.
Real-time detection and control of the valve opening degree enable closed-loop control. The full operation of the oxygen sensor significantly shortens its service life.
When changing the detection sequence, perform a short-duration smoke detection and adjustment each time ignition occurs. Then, close the smoke passage leading to the oxygen sensor, set an appropriate detection threshold before the smoke level exceeds the reference value, and finally close the sensor’s smoke passage to protect the oxygen sensor and prevent poisoning.
In addition, each time the ignition is triggered, the system adjusts the oxygen sensor’s sensitivity to reduce its sensitivity curve and fine-tunes the detection accuracy based on the adjusted parameters, thereby preventing any degradation. This significantly extends the service life of the oxygen sensor.
However, the intermittent regulating gas valve can only be used for this type of immediate application. Thermal-mode regulation is another adaptive thermal-coupling method that detects flame temperature.
Under the condition of constant gas flow, by adjusting the air flow, each group has three different air-flow settings. The middle air-flow setting results in the highest flame temperature as detected by the thermocouple. At this setting, the opening of the current electrical control valve matches the current air flow. Excess air and insufficient air, on the other hand, will both lower the flame temperature. The fire-resistant furnace we’re introducing is a true wall-mixing furnace that boasts high efficiency and energy savings. If you’d like to learn more, feel free to contact us anytime!