What “Efficiency Testing” Means in Boilers

• standby losses. You perform a combustion efficiency test when the boiler is operating under a steady load. Therefore, the combustion efficiency test does not reveal standby losses, which occur between firing intervals. You cannot measure standby losses directly. You have to estimate them from the type of boiler and the firing schedule.
• heat loss from the surface of the boiler to the surrounding space. As a practical matter, you cannot measure this loss. Typical estimates state that the loss from surface radiation is about two percent of the boiler’s full load energy consumption.
• blowdown loss. The amount of energy wasted by blowdown varies over a wide range.
• soot blower steam. The amount of steam used by soot blowers is a variable that depends on the type of fuel and the judgement of the staff.
• auxiliary equipment energy consumption. The combustion efficiency test does not account for the energy use by auxiliary equipment, such as burners, fans, and fuel pumps.

While the combustion efficiency test does not give the overall efficiency of the boiler plant, it is by far the easiest method of tracking moment-to-moment, day-to- day, and season-to-season variations of boiler efficiency. Combustion efficiency testing tells you how far boiler efficiency drifts away from the best efficiency that you can achieve when the boiler is fully tuned up.