Is It True That the Thermal Efficiency of Gas-Fired Condensing Boilers Can Exceed 100%?

Many users have doubts about the claim that the efficiency of condensing boilers produced by Jiuxu Boiler can reach over 100%. In their view, the definition of boiler efficiency is the ratio of the useful energy generated during boiler operation to the energy input into the boiler, i.e., Boiler Efficiency = Useful Energy / Total Input Energy. Based on this analysis, if the efficiency exceeds 100%, doesn’t that mean the useful energy of the condensing boiler is now greater than the input energy?

In fact, the heat generated after fuel combustion is divided into higher heating value (HHV) and lower heating value (LHV). The higher heating value is the direct thermal efficiency of the boiler that we usually refer to; however, the lower heating value should not be overlooked. If used properly, the combination of the two makes it possible for the thermal efficiency of the condensing boiler to exceed 100%.

To achieve the ultra-high thermal efficiency of over 100% for gas-fired condensing boilers, the following aspects must be properly implemented:

First, appropriately increase the heating surface area of the boiler, and use corrosion-resistant materials for the tail equipment of the condensing boiler, such as the main heat exchanger and flue gas channels.

Second, change the original combustion method of the combustion system to a proportional adjustment combustion method to ensure stable and efficient combustion.

Finally, add a condensed water discharge system. After these measures are completed, the exhaust gas temperature of the condensing boiler can be reduced to below 80°C. As the exhaust gas temperature decreases, the efficiency of the condensing boiler naturally increases. The reasons for this come from two aspects:

When the exhaust gas temperature decreases, the heat loss through exhaust gas of the boiler also decreases accordingly. Since heat loss through exhaust gas is the main heat loss of gas-fired boilers, reducing this heat loss will naturally increase the efficiency.

When the exhaust gas temperature drops below 100°C, the water vapor in the flue gas will condense into water. The heat released during the condensation of water vapor can be absorbed by the boiler, thereby further improving the overall efficiency of the condensing boiler. Generally, approximately 2500 kilojoules of heat can be released when 1 kilogram of water vapor condenses into liquid water. It is precisely because the boiler absorbs this additional heat and converts it into useful heat for the boiler that the efficiency of the boiler is improved.

From this, it can be seen that it is feasible for the thermal efficiency of gas-fired condensing boilers to exceed 100%.