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NORA Oilheat Technicians Manual

Figure 4-21: Delayed oil valve 4-18 Fuel Units and Oil Valves Figure 4-22: Construction detail with valve closed Chapter 4 Fuel Units and Oil Valves Stem Coil Fuel Flow Spring Piston Seat Orifice Body Figure 4-22: Construction detail with valve open Fuel Flow Operation of the delayed action solenoid valve The delayed oil valve may also help in preventing a puff back as a result of poor ignition. During startup, the burner motor requires a substantial starting current. This current requirement may rob voltage from the ignition system, resulting in a weak spark at the electrodes. When the motor reaches operating speed, the current requirement of the motor drops appreciably and the full supply voltage is available to the transformer. This results in maximum ignition voltage at the time the delayed oil • Operating problems with the burner can signify a leak, and any air in the oil pump call, poor pump cut-off, noisy operation, and erratic fire calls, loss of flame retention (flame pulsates on the end cone), loss of oil prime, rough starts or shut downs, pump whine and pressure fluctuation, and after drip could all indicate a leak. In order to check for leaks in the suction pipe and fittings you must first run an operating vacuum test, covered earlier in the chapter. Valves Solenoid oil valves Not allowing oil to flow until the burner is up to full speed and air flow into the heat exchanger has been established can make for cleaner start up. The use of a solenoid oil valve can delay fuel delivery to the nozzle for anywhere from 4 to 15 seconds after burner startup. Figure 4-21 shows an oil valve. To achieve a longer delay. a primary control with a valve-on delay feature and a non-delay valve should be used. On burner shutdown, the oil valve closes immediately, providing a much more rapid shutdown than is obtainable with the pressure control valve on the fuel unit. Figure 4-22 shows how the valve works. In operation, this valve can solve many problems associated with poor startup and shutdown conditions such as: 1. Pulsating starts 2. Puff back 3. After fire as a result of a malfunctioning pressure regulating valve 4. Long term soot buildup in heat exchanger resulting from incomplete combustion on burner startup and shutdown


NORA Oilheat Technicians Manual
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