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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 improve, people are placing increasing emphasis on the comfort of their home environments. Wall-mounted boilers meet both heating and domestic hot‑water needs, and their dual‑purpose design is widely appreciated.
When choosing a wall‑mounted boiler, “energy efficiency” is a key consideration. So let’s explore whether fully premixed wall‑mounted boilers truly deliver high efficiency and energy savings. Fully premixed wall‑mounted boilers rely on two core technologies: full‑mix combustion and condensing technology. What distinguishes conventional combustion from fully premixed combustion? Conventional Combustion In standard combustion systems, the gas flow rate is adjusted via a proportional valve to modulate the load. While this allows control of the gas supply, the intake air volume remains fixed. Because the gas–air mixture never achieves the ideal stoichiometric ratio for complete combustion, thermal efficiency is relatively low. Fully Premixed Combustion In contrast, fully premixed wall‑mounted boilers achieve combustion only after thoroughly mixing air and gas. This approach results in rapid combustion, higher flame temperatures, more complete burning, a lower excess‑air ratio, and superior thermal efficiency. Why Are Fully Premixed Boilers More Energy‑Efficient? They employ full‑premix combustion, where the precise amount of air required for complete combustion is supplied along with the fuel. If too little air is provided, combustion becomes incomplete; if too much air is introduced, it leads to unnecessary heat loss. By maintaining an optimal air‑to‑fuel ratio under all operating conditions, fully premixed boilers ensure thorough combustion, eliminate excess air, and maximize energy recovery. Condensation of Flue Gases Fully premixed wall‑mounted boilers reduce flue gas temperatures, causing water vapor in the exhaust to condense. This process recovers nearly all sensible heat and a portion of the latent heat of vaporization, significantly improving overall efficiency. By contrast, conventional boilers operate at much higher exhaust temperatures, leaving the latent heat of water vapor largely unrecovered.
Meanwhile, high flue gas temperatures carry away sensible heat, reducing thermal efficiency; fully modulating boilers are more energy‑efficient than conventional wall‑mounted units. A mature wall‑mounted technology is the oxygen‑sensor‑based adaptive system. However, oxygen sensors can suffer from poisoning, which degrades their performance over time and may lead to reduced detection sensitivity with prolonged use.
Real-time detection and control of valve opening ensure closed-loop operation. Full‑range operation of the oxygen sensor significantly reduces its service life.
When changing the detection sequence, perform a brief smoke‑based test and adjustment each time the ignition is engaged, then close the smoke‑intake passage to the oxygen sensor. Set an appropriate detection threshold before the smoke level exceeds the reference value, and finally shut off the sensor’s smoke‑intake channel to protect the oxygen sensor and prevent 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 parameters, thereby preventing any degradation. This significantly extends the oxygen sensor’s service life.
However, the intermittent gas‑regulating valve can only be used for such immediate applications. Thermal‑coupling–based flame‑temperature sensing is another adaptive approach.
With the gas flow rate held constant, varying the air flow yields three distinct air‑flow settings per group. The middle setting produces the highest flame temperature, as measured by the thermocouple; at this point, the electrical control valve is fully open, matching the current air‑flow rate. Excess air or insufficient air will lower the flame temperature. The fire‑box described here is a full‑wall‑mixing furnace that delivers exceptional efficiency and energy savings. If you’d like to learn more, please don’t hesitate to contact us!
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