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NORA Oilheat Technicians Manual

Oil Line Start HelperTM Chapter 5—Nozzles and Combustion Chambers 5-13 hits the back wall, which also increases smoke. The thick stream of oil makes for larger droplets that result in delayed ignition and smoke. Suddenly, the appliance is full of soot. Fortunately, as the oil gets colder, so does the air. This increases draft. The stronger draft draws in more combustion air and helps accommodate the increased volume of combustion gases. This can happen to a lesser degree to underground tanks that are normally at about 50 to 55° F, and even to indoor tanks that are at room temperature. As oil trucks are not heated, it takes several days for a fresh load of cold oil to warm up in an underground or indoor storage tank. Until the oil warms, you can have viscosity problems. See Figure 5-12. The easiest way to cut down on the effects of cold oil is to increase pump pressures. This decreases droplet size and better defines the spray angle, which makes burners less susceptible to high viscosity Fuel Flow (gal./hr.) Figure 5-14 Figure 5-13: Nozzle line pre-heater Fuel Flow During Startup With and Without Pre-Heater Chapter 5 Nozzles and Chambers Electrode Insulator Assembly Nozzle Static Plate Pre-Heater Seconds From Start oil. Remember, it also increases the flow rate, so size the nozzle correctly. Another solution to cold oil is to install a nozzle line pre-heater. This simple, strap-on device increases the temperature of the oil arriving at the nozzle to about 100 to 120° F. See Figures 5-13 and 5-14. The nozzle line heater is wired in parallel with the limit control so it is energized whenever there is power to the heating system. It works on electrical resistance. When the resistance gets too high, it stops heating. As the unit cools, the resistance drops and it heats up again. Preheaters draw about one amp and only heat the fuel to about 80 degrees above the ambient temperature—between 120 and 130°F—during stand-by. When the burner is running, the cold oil brings the temperature well below


NORA Oilheat Technicians Manual
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