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NORA Oilheat Technicians Manual

Chapter 7 Combustion Figure 7-20: Relationship between excess air and CO2 Percent Excess Air Percent CO2 in Flue Gas 7-20 Combustion Measure Percent CO to Determine 2 Percent Excess Air To add air from an adjacent room, two openings between the room could be made 12 inches above the floor and 12 inches below the ceiling. The size of these openings is based on 1 square inch per 1,000 Btu input. To add air directly from the outside of the structure, two openings could be made. The size of these openings is based on 1 square inch per 4,000 Btu input. The above requirements are based on guidelines in NFPA 31 or NFPA 54. Alternately, if operating in a confined space, additional air may be added by a duct to the outside, sized on 1 square inch per 5,000 Btu input. Incomplete air-oil mixing Improper mixing creates fuel rich and fuel lean pockets in the combustion area and prevents complete burning. Some of the causes are: • Mismatch of the fuel droplet spray and the burner air pattern • Inadequate air swirl and turbulence caused by outdated burner design • Improper burner head size • Improper adjustment of air handling parts of the burner • Irregular or unbalanced fuel spray caused by a partially plugged nozzle • Off center installation of the nozzle • Dirt or soot accumulation on burner air forming parts or air fan blades • Defective or damaged burner parts such as the end cone, air tube, fan, and motor coupling • Using a nozzle that is either too small or too large for the burner head and combustion area • Fuel pump pressure set too low or too high • Cold oil producing larger fuel droplets, and increasing the firing rate beyond the air setting


NORA Oilheat Technicians Manual
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