The classic fire triangle consists of three elements required to make a fire: heat, fuel and oxygen. Insufficient air rich in oxygen is the main cause of incomplete combustion. The secondary cause is contaminated fuel. The byproduct of incomplete combustion is carbon-rich soot. These factors result in carbon buildup inside the combustion chamber and on burner nozzles, and also by reducing the flue’s inside diameter. Reducing the diameter restricts the exhaust process and reduces the amount of fire-sustaining oxygen in the combustion chamber.
A critical part of oil furnace design is minimizing carbon buildup by controlling soot production. This goal is accomplished by providing sufficient oxygen, backed by an efficient combustion air delivery system. Whereas smaller furnaces are fired by a correctly sized pressure-jet burner equipped with an integral blower, larger furnaces require a separate combustion air blower powerful enough to provide sufficient pressure to overcome furnace back-pressure or “resistance.” In some cases a secondary flue-mounted exhaust fan is required to complete the process.
Carbon buildup inside the combustion chamber, on oil burner nozzles and inside exhaust flues is not only caused by insufficient combustion air, but also by fuel oil contaminated with one or more noncombustible substances. Consequently fuel quality control backed by an efficient fuel-oil filtering system, are both vital aspects when it comes to controlling carbon build-up in your home's oil-fired furnace.
- Jupiterimages/Comstock/Getty Images