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Are fully premixed wall-mounted boilers really efficient and energy-saving?
Release Date:
2022/05/25 10:14
As living standards continue to rise, people are placing greater emphasis on the comfort of their home environments. Wall-mounted boilers effectively meet both heating and domestic hot-water needs, and their dual-function design is widely appreciated.
When choosing a wall-mounted boiler, “energy efficiency” is a key consideration. So let’s take a closer look: are fully premixed wall-mounted boilers truly highly efficient and energy-saving? Fully premixed wall-mounted boilers primarily incorporate two technologies: fully premixed combustion and condensing technology. What is the difference between conventional combustion and fully premixed combustion in wall-mounted boilers? Conventional Combustion In standard combustion systems, the load is adjusted by modulating the opening of the gas proportioning valve. Under this approach, the gas flow can be regulated, but the air intake cannot. Because the gas–air mixture never achieves the stoichiometric ratio required for complete combustion, the thermal efficiency of this combustion method is quite low. Fully Premixed Combustion In fully premixed wall-mounted boilers, combustion occurs only after the air and gas have been thoroughly mixed. This type of combustion is characterized by rapid flame propagation, high flame temperature, complete combustion, a low excess air coefficient, and high thermal efficiency. Why Are Fully Premixed Wall-Mounted Boilers Energy-Efficient? First, they employ fully premixed combustion. The amount of air supplied for gas combustion is precisely calibrated to ensure complete combustion; if too little air is provided, combustion will be incomplete. Unlike conventional wall-mounted boilers, fully premixed combustion maintains the optimal air–fuel ratio at all load levels, enabling complete combustion with no excess air. This results in more thorough combustion and greater energy savings. Condensing Flue Gases Fully premixed wall-mounted boilers reduce flue gas temperatures to condense the water vapor contained in the exhaust, thereby recovering nearly all of the sensible heat and a portion of the latent heat of vaporization. This significantly enhances overall energy recovery. By contrast, conventional wall-mounted boilers operate at much higher flue gas temperatures, so the latent heat of vaporization in the exhaust cannot be recovered.
Meanwhile, high flue-gas temperatures carry away sensible heat, reducing thermal efficiency; fully mixed combustion boilers are more energy-efficient than conventional wall-mounted boilers. A mature wall-mounted boiler technology is the oxygen-sensor-based adaptive system. However, oxygen sensors can be poisoned, leading to long-term degradation of detection sensitivity.
Real-time detection and control of the valve opening degree are implemented to achieve closed-loop control. Full-operation of the oxygen sensor significantly shortens its service life.
When changing the detection sequence, perform a brief smoke detection and adjustment each time the ignition is engaged, then shut off the smoke supply to the oxygen sensor. Before the smoke level exceeds the reference threshold, set an appropriate detection threshold, subsequently close the smoke supply line to the sensor, and thereby protect the oxygen sensor from poisoning.
In addition, each time the engine is started, the system adjusts the oxygen sensor’s sensitivity to flatten its response curve and recalibrates the detection accuracy based on the reduced sensitivity, thereby preventing any degradation in performance. This significantly extends the service life of the oxygen sensor.
However, the intermittent gas-regulating valve is only suitable for such immediate use. Pattern-based regulation is another adaptive thermal-coupling method for detecting flame temperature.
With the air volume held constant, varying the airflow results in three distinct flow settings per cycle; the middle setting yields the highest flame temperature as measured by the thermocouple, at which point the opening of the electric control valve matches the current airflow. Excess air or insufficient air, however, will lower the flame temperature. Our fully wall-mixed furnace is renowned for its exceptional energy efficiency. If you would like to learn more, please feel free to contact us at any time!
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