TM 1-1520-240-102-4-2 energize the pump. When switch is at OFF, the relaycircuits open and power from the No. 1 and No. 2 AC busis de-energized thus shutting off the pump. Power issupplied for these relay circuits by the No. 1 and No. 2 DCbus through the LH and RH FUEL PUMP CONT - AUXAFT, MAIN AFT, MAIN FWD, and AUX FWD circuitbreakers on the No. 1 and No. 2 PDP. Power is suppliedto the pumps circuits by the No. 1 and No. 2 AC busthrough the LH and RH FUEL PUMPS - MAIN FWD,MAIN AFT, AUX FWD, and AUX AFT circuit breakers onthe No. 1 and No. 2 PDP. b.AUX PRESS Indicating Lights. Each light iselectrically connected to the forward and aft auxiliarytank pressure switches. When this indicating light illumi-nates, it indicates that the fuel pressure in either theforward or aft auxiliary fuel line is below 10 $1 psi. Theauxiliary tank fuel boost pump switches must be at ON toprovide electrical power to the indicating light. The lightintensity can be adjusted by turning the light housing.Power is supplied to operate the indicating light by theNo. 1 and No. 2 DC bus through the LH or RH Fuel PUMPCONT AUX FWD & AUX AFT circuit breakers on the No.1 and No. 2 PDP. c.XFEED Switch. The switch electrically operatestwo fuel valves in the crossfeed line. The switch has anOPEN and CLOSE position. When the switch is atOPEN, power from the No. 1 DC bus opens the fuelvalves through the XFEED CONT circuit breaker on theNo. 1 PDP. When the switch is at CLOSE, electrical pow-er closes the valves.2-4-5. Fuel Valves.There are two engine and two crossfeed fuel valves.a.Engine Fuel Valves. One engine fuel valve (fig.2-4-2) is in the fuel supply line to each engine. The valveis electrically operated by the FIRE PULL handles andmanually by a lever on the valve. They are located at sta.498 and labeled FUEL VALVE # 1 ENGINE and FUELVALVE # 2 ENGINE.b.Crossfeed Fuel Valves. The crossfeed fuelvalves connects the No. 1 and No. 2 engine fuel lines.When the valve is opened, both engine fuel feed lines areinterconnected and fuel can be supplied from both fueltanks to feed either engine or from either tank to feedboth engines. Fuel cannot be transferred between tanks.The valves are electrically operated by the XFEEDswitch on the FUEL CONTR panel or manually by a leveron the valve. They are labeled FUEL VALVE CROSS-FEED and located at station 504.c.FUEL VALVE WARNING LIGHT. There are twoPRESS-TO-TEST FUEL VALVE WARNING LIGHT nextto each FUEL VALVE CROSS FEED Figure 2-4-2. Engine Fuel Valves, Sta. 498and two PRESS-0TO-TEST FUEL VALVE WARNINGLIGHT next to FUEL VALVE # 1 ENGINE and # 2 EN-GINE (fig. 2-4-3). They indicate the operating conditionof the individual valve and associated circuitry. Power issupplied to operate the crossfeed FUEL VALVE WARN-ING LIGHT by the No. 1 DC bus through the XFEEDCONT circuit breaker on the No. 1 PDP. Power is sup-plied to operate the engine FUEL VALVE WARNINGLIGHT by the DC essential bus through the ENGINE NO.1 and NO. 2 FUEL SHUT-OFF circuit breakers on the No.1 and No. 2 PDP.The following description on when the light will illuminateis for the XFEED switch. The same result applies to theengine fuel valves with the FIRE PULL handles.(1)Each time the XFEED switch is moved fromCLOSE to OPEN or OPEN to CLOSE. After this opera-tion, the light should extinguish, indicating the crossfeedvalve is synchronized with the switch position.(2)When a short circuit occurs, causing a signalto be applied opposite to the valve position. However, thevalve will remain at the position last selected by XFEEDswitch.(3)When the crossfeed valve protection relayfails. The crossfeed valve will remain at the last selectedposition and the valve can be operated electrically ormanually, as required.
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