Chapter 4 Efficiency Improvements with New Oilheat Technology Oil Burners The oil burner makes or breaks the efficiency of a heating system. Today’s oil burners convert 99.99% of the energy in the fuel into heat. The challenge is to be sure the heat exchanger of the boiler, furnace, or water heater transfers as much of this energy to the living space or domestic hot water as possible and the venting system safely removes the combustion gases from the heat exchanger and the building. Flame Retention versus Conventional Burners The main difference between conventional (pre-1972) and flame retention (post-1972) burners is the way combustion air and fuel are combined. The flame retention burner has a specially designed combustion head (end cone) and a high-pressure fan that produces more recirculation within the flame for better fuel-air mixing. The swirling air pattern increases the contact between the fuel droplets and the air. In addition, a recirculation zone is formed within the flame. Flame retention burners operate with less excess air than older burners’ designs. Flame retention burners require 20 to 30% excess air; older burners need 50 to 100% excess air to achieve low smoke numbers. Lower flue heat loss for these burners translates into a fuel savings of more than 10%. The static pressure increase with flame retention is dramatic. Static pressure is needed to overcome the restriction in the heat exchanger, and the increase in static pressure allows furnace and boiler manufacturers to make more 24 National Oilheat Research Alliance restricted heat exchangers, which are more efficient. High static pressure burners push against the increased restrictions in the heat exchangers for clean, quiet, and efficient oil combustion. To ensure the new burners produce the necessary static pressure, make sure the air handling parts are clean. It is also important to be sure the air guides, gaskets, and blower wheels are installed properly. Fourth Generation Flame Retention Oil Burners Flame retention burners have continued to improve since their introduction in the early seventies. The result is today’s burners are much better than those manufactured even as recently as the 1990's. Today's flame retention head burners produce more effective fuel-air mixing than outdated designs. This reduces the amount of excess combustion air required for clean burning, produces higher flame temperatures and increases boiler and furnace heat transfer rates. All this results in lower heat losses and improved efficiency. Because they require less excess air, the air intake on the new burners is not as open as on older burners. This dramatically reduces offcycle airflow through the heating system. The result is much lower on-cycle and off-cycle losses and greater efficiency. These burners often burn so clean that almost no combustion residue builds-up over the
NORA Advanced Efficiency
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