Useful Heat Delivered to Home of about 28%, with a typical range of 20% to 30% of the total heat content of the fuel. This can be separated into 6.5% from water vapor loss and about 20% from excess air heat loss. The performance of many older systems could be improved significantly by replacing the burner with a flame retention burner. However, the most effective way to reduce excess air losses is with a new boiler or furnace. New oil appliances operate very efficiently with on-cycle heat losses ranging from 9% to 14%. Combustion air normally enters the National Oilheat Research Alliance 11 Figure 1 Heat Loss Flue Heat Loss During Burner Operation (On-cycle Losses) One of the largest heat losses in a building is the heat that goes up the flue while the burner is running. The oil flame produces hot gases that pass through the heat exchanger and up the chimney, Figure 2. Most of the heat contained in these gases is transferred to the heating system water or air that is then transferred to the living space. Combustion efficiency tests measure flue loss. Flue losses that occur when the burner is running are divided into two parts: water vapor heat loss and excess air (sensible) heat loss. This is the heat carried out of the building with the hot exhaust gases. On-cycle heat losses for oilheating units vary depending on heating equipment design and servicing. Studies show average on-cycle losses (as measured by CO2 and net stack temperature) for burners installed before 1980 Figure 2 Flue Heat Loss Flue Heat Loss (On and Off Cycle) Jacket Heat Loss Air Infiltration Induced by the Heating System and Chimney Fuel Energy Boiler or Furnace Water Vapor Loss Fixed Property of Fuel Sensible Heat Loss Depends on Volume of Exhaust Gases Burner Adjustment Affects Sensible Heat Loss
NORA Advanced Efficiency
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