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How Oxygen Levels Affect High-Efficiency Boilers

Life on earth requires oxygen in some form or another. The high-efficiency condensing boiler is not a living thing, but it operates in a system that needs oxygen to function optimally. As such, high-efficiency boilers are very much like us.


Let's take a look at how it works.


Condensation occurs when water vapor changes into a liquid. A pound of condensed water vapor contains approximately 1,000 BTUs of latent energy. By condensing the combustion exhaust gas, latent energy is extracted from the gas and used to heat the water, enhancing boiler efficiency.


When starting up a high-efficiency boiler, the combustion gas must be calibrated. The installation process is outlined in detail in the installation manuals of all manufacturers. Manufacturers calibrate the equipment at the factory. Due to changes in local altitude, gas BTU content, gas supply piping, and supply regulators, recalibration is required during initial startup. The unit will never perform at its optimal level if the combustion gas is not recalibrated during installation. This practice has the limitation that the technician can only adjust the air/fuel mix when the operating conditions are exactly right.


In order to maximize efficiency, advanced combustion control systems must maintain precise air-to-fuel ratios. Equipment can often deviate from the ideal air/fuel ratio due to environmental variations such as humidity, atmospheric pressure, gas energy content, etc.


By maintaining optimal oxygen levels, you can maximize efficiency and save money. Increasing oxygen availability decreases the exhaust gas's dew point. The lower dew point means the unit will only be in condensing mode when very low-temperature water is returned to it. There are no high efficiencies or savings when the unit isn’t condensing.


Alternatively, as the level of oxygen decreases the exhaust gas dew point temperature increases, leading to a higher return water temperature requirement. The boiler will operate in condensing mode, at high efficiency, most of the time.


There is a diminishing returns effect in oxygen content and performance for the unit. Too much available oxygen will lead to inefficient combustion. Over time, the unit will require unscheduled maintenance. Too little available oxygen causes unstable combustion and increased emissions. This will lead to flame loss faults and, once again, unscheduled maintenance.


Increasing reliability, improving efficiencies, and reducing emissions sound like the ideal formula for condensing boiler success. Make sure your boilers are getting the oxygen they need.

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