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NORA Oilheat Technicians Manual

Second Stage Gearset One pipe system Most of today’s Oilheat systems require only a suction line to bring the oil from the tank to the burner. We call these one pipe systems. Older single stage fuel units should be piped only as one pipe where oil can flow to the unit under gravity conditions; that is, the burner is located level with or lower than the bottom of the oil tank. Newer single stage pumps operate at a maximum of 6" of vacuum on a one pipe system. They can create much more, but the oil will begin to give us trouble over 6". If your calculated vacuum is less than 6" and you are using a new fuel unit, it should be installed one pipe. Two pipe system If more than 6" of vacuum is required, a 4-6 Fuel Units and Oil Valves To Strainer Legend single stage fuel unit should be piped with a return line to the tank or fuel de-aerator. This is called a two pipe system. An example of such an installation would be an abnormally long run from the oil tank to the unit. If a single stage fuel unit two pipe system has an operating intake vacuum over 10", unstable flame conditions, carboned-up firing assembly, after fire, and noisy flame may result. High vacuum may also shorten the life of the fuel unit. Two stage fuel unit, two pipe system If more than 10" of vacuum is required, you should install a two stage pump or booster pump. The two-stage fuel unit has two sets of fuel pump gears. The first set purges the pump of air and supplies an Piston Assembly Pressure Gauge Port Optional Return Pressure Adjusting Screw High Speed Models to Strainer Low Speed Models to Seal Chamber Lip Seal Input Shaft Return to Tank By-pass Plug First Stage Gearset Intake From Tank Positive Strainer Cone Valve Nozzle Port Diaphragm Valve Chapter 4 Fuel Units and Oil Valves Figure 4-5: Suntec Industries; cutaway example two-stage fuel unit Suction Gear Set Pressure Return Nozzle Pressure


NORA Oilheat Technicians Manual
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