How High Efficiency Condensing Gas Boilers Work?

Whether you use them for home heating or for supplying hot water to your company, condensing gas boilers are the most efficient sources of heating water in a hydronic heating arrangement. The following is a brief description of how high efficiency condensing gas boilers work that includes - meaning of high efficiency of boiler operation, and various types of components in a condensing gas boiler.
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What is Combustion?

Combustion is an exothermic reaction that occurs on mixing the air and fuel rapidly in a proper ratio. When air is mixed with hydrocarbons such as natural gas, oil, and propane, it produces products of combustion such as heat, carbon dioxide, and water vapor. These make up the ‘flue gases' that pass out of the boiler through the flue or chimney.

Why condensing gas boilers are highly efficient?

For hundreds of years, boilers have been used in hydronic heating systems in order to generate and move hot water via pipes and deliver heat. These are different than furnaces, which move water instead of air through them. Until 25 years ago, home heating boilers were efficient about 80-85% with flue gas temperatures typically around 350°F. A high efficiency boiler has the flue gases with temperature usually around 135°F and efficiencies of 95% or greater. This is the reason why high efficiency boilers have higher efficiency, due to extracting more heat from combustion out of the flue gases and putting it into the hydronic system. Not only this, these products are so efficient that they are capable of pulling so much heat out of the flue gases that the water vapor in these gases gets cools and condenses, that changes their state from vapor to liquid. Therefore, the name is condensing gas boiler.


Additionally, the combustion air fan can control its speed better as compared to a single stage, complete on or off device that is found on typical mid-efficiency boilers. This capability of modulation means that the blower can adjust its speed to the variable inputs needed during the fall and spring months. This is yet another reason behind the high- efficiency of the condenser gas boilers.

How a gas condensing boiler functions?

A gas condensing boiler heats up the water through the heat of combustion. The resultant flue gases generally exit through the chimney as a result of which the energy contained in the flue gas gets wasted. But, the condensing technology exploits these gases by extracting the flue gas heat and feeding the energy attained into the heating circuit.

To gain energy, it is important for the water vapor to get condensed. The condensation process takes place at a temperature below 56 °C. This happens when a condenser boiler cools the vapor through a specifically designed heat exchanger. The energy gained is further used to heat the cold water. The hot water flows into the primary heat exchanger where it is further heated to reach the desired temperature. Small amounts of waste water occur during this process which must be disposed of. This waste water does not require any further neutralization as the acidity of the waste water very low and can be conducted into a normal drainage system.

Source by Canaan Portillo


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