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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A

757 MAINTENANCE MANUAL
 (c)  
The vent connection is connected to the high and low-differential-pressure-servo assemblies, the electro-magnetic-control valve, the reference pressure regulator, and to ambient.

 (d)  
Ice in the condensor causes one of the servo assemblies to open when it blocks the air that flows through the condensor. Thus, the pressure upstream of the ice increases and the pressure downstream of the ice decreases. The pressures upstream and downstream of the ice are transmitted to the inlet chambers of the servo assemblies. If the upstream pressure is sufficient, it pushs the actuator rod and open the poppet valve. Thus, air flows from the vent connection, through the poppet valve, to the open chamber of the pneumatic actuator. This causes the low-limit-control valve to open so that hot air can flow to the turbine outlet to melt the ice. 1) The condensor inlet is the upstream pressure and the

 condensor outlet is the downstream pressure for the high-differential-pressure-servo assembly. The turbine outlet is the upstream pressure and the pack outlet is the downstream pressure for the low-differential-pressure-servo assembly. Ice between the upstream and the downstream pressures will cause the applicable servo assembly to open.

 (e)  
The standby-pack-temperature controller or the applicable (left or right) automatic-pack-temperature controller supplies the electrical current to the torque motor of the electro-magnetic-control valve. The electrical current causes the torque motor to move the flapper away from the supply nozzle port. When the supply nozzle port is open, air flows from the vent connection to the open chamber of the pneumatic actuator. Thus, the low-limit-control valve opens to let air flow around the air cycle machine. The smaller amount of air in the air cycle machine causes it to operate more slowly, so that the compressor outlet temperature is decreased.

 K.  Temperature Control Valve (Fig. 10)_________________________
 (1)  The temperature control valve is used to control the temperature of the air-cycle-machine-compressor outlet. To do this, it controls the amount of air that flows through the air cycle machine. If more air flows through the temperature control valve, then less air flows through the air cycle machine. The less air that flows through the air cycle machine, the slower it operates. Thus, the temperature at the compressor outlet decreases.
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A

757
MAINTENANCE MANUAL

VISUAL  ELECTRICAL 
POSITION  MOTOR 
SEE  A  INDICATOR 
ROTARY 
ELECTRO-
MECHANICAL 
ACTUATOR 
MANUAL 
CAPACITOR  OVERIDE 

VALVE 
RESISTOR  BODY 
ADAPTOR 
ASSY 
VISUAL POSITION INDICATOR  ELECTRICAL MOTOR  LINEAR VARIABLE RESISTOR ASSY  RESISTOR COVER 
FULL OPEN 
LIMIT SWITCH 
FULL CLOSE  REDUCTION GEAR 
LIMIT SWITCH  A 
ROTARY 
ELECTROMECHANICAL 
SECONDARY WORM  ACTUATOR 
GEAR SHAFT 
MANUAL  SLIP CLUTCH 
OVERRIDE 
PRIMARY WORM 
SECTOR GEAR  GEAR SHAFT 
BUTTERFLY 
PLATE ASSY 
VALVE BODY 
AIR  ASSY 
FLOW 
SHOULDERED 
LINEAR  SHAFT 
VARIABLE 
RESISTOR  LINEAR VARIABLE 
(10K OHMS) RESISTOR (1K OHMS) 
Temperature Control Valve 
Figure 10 

EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

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