It is important to understand that a boiler in a commercial application (can also apply to residential boiler applications) is going to consume a large amount of the energy budget therefore it is important to track efficiencies because a slight drop in the boilers efficiency can cause a sharp increase in the energy costs. Understanding that, we all know it is important to have good HVAC boiler preventive maintenance practices and regular HVAC boiler system tune-ups including maintenance on boilers. When we talk about boiler efficiency we talk about two related types of boiler efficiencies and both can have an impact on the boiler energy budget. There is boiler efficiency and there is combustion efficiency. A decrease in boiler combustion efficiency will decrease boiler efficiency but not necessarily vice versa.

    * Boiler Combustion Efficiency is measured by dividing the usable heat produced in the boiler by the fuel input to the boiler in BTU/h content. This calculation is based on the actual heat available produced by the boiler system after heat loss up the boiler stack and other boiler heat losses which do not provide usable heat. Boiler excess air is partially responsible for the boiler heat loss but it is necessary to complete the boiler combustion process. Therefore it is important that the boiler burner system is tuned and monitored on a regular basis. Using combustion analyzers the O2 and boiler stack temperatures can be monitored for spikes which will alarm the boiler maintenance crew about possible boiler problems. It is important to maintain good boiler combustion efficiency for overall boiler efficiency.
    * Boiler Efficiency is measured by dividing boiler combustion losses, radiant heat losses from the boiler jacket and near boiler piping, and boiler unknown losses (losses from tube scaling, soot build-up (exchanger thermal efficiencies)) by total fuel input to the boiler in BTU/h. Much of boiler efficiency is determined by combustion efficiency and a lot of boiler maintenance departments focus on boiler combustion efficiencies and ignore the other boiler heat losses.
    * Boiler Thermal Efficiency is related to how efficient the boiler heat exchanger is working. Things like boiler soot build-up or boiler water scaling can reduce the efficiency of a boiler.
    * Boiler Steady-State Efficiency is the efficiency of the boiler running full blast under maximum load.
    * Boiler Overall Seasonal Efficiency is important to track to see if there is an annual degradation in boiler efficiency. It gives you the big picture from year to year for comparison of boiler efficiency.

To get the most out of your boiler system it is necessary to implement a complete boiler maintenance/efficiency plan to maintain every aspect of boiler efficiency. Providing that a boiler maintenance/efficiency plan is put into place and qualified boiler technicians perform the boiler tuning with the appropriate tools a cost savings in energy use can be realized.

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