AIR CONDITIONING -PACK FLOW CONTROL -FUNCTIONAL DESCRIPTION -ASCPC FLOW CONTROL

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777 AIRCRAFT MAINTENANCE MANUAL

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21-52-00

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BOEING PROPRIETARY -Copyright # -Unpublished Work -See title page for details.

AIR CONDITIONING -PACK CLG AND MIX MANIFOLD TEMP CONTROL -INTRODUCTION

Purpose
Pack cooling and mix manifold temperature control operates the pack to control pack discharge air temperature to a value that supplies sufficient cooling air to the flight deck and the mix manifold.
General Description
The air conditioning (A/C) pack has components that give these functions:
*
Ram air and heat exchanger cooling

*
Air cycle machine cooling

*
Water removal.

Air from the flow control system usually flows through the pack in this sequence:
*
Primary heat exchanger (PRI HX)

*
Air cycle machine (ACM) compressor

*
Secondary heat exchanger (SEC HX)

*
Over the reheater and condenser cores

*
Water collector

*
Reheater

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ACM turbine 1

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Condenser

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ACM turbine 2

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Conditioned air check valve

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Mix manifold.

Air from the pack mixes with recirculated air in the mix manifold. This air moves through the distribution system to the passenger cabin zones. The flight deck gets air directly from the left pack.
The ram air part of the pack keeps the compressor outlet temperature in limits. It also gives pack outlet temperature control.
The right pack operates the same as the left pack.
See the functional description page on pack cooling and mix manifold temperature control in this section for more information about pack operation (SECTION 21-52).
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AIR CONDITIONING -PACK CLG AND MIX MANIFOLD TEMP CONTROL -INTRODUCTION

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AIR CONDITIONING -PACK CLG AND MIX MANIFOLD TEMP CTRL -COMPONENT LOCATIONS

Component Locations
Most of the pack cooling and mix manifold temperature control components are in the ECS bay. Four mix manifold temperature sensors are in the aft part of the forward cargo compartment (not shown). The left and right ECS bays have a pack, a conditioned air check valve, and ram air system components (not shown).
The ram air system component locations are described in another part of this section.
Each pack has these components:
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Economy cooling valve

*
Water collector

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Low limit valve

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Water overflow

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Water spray nozzle

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Temperature sensors (10 places)

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Economy cooling check valve

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Dual heat exchanger

*
Fan bypass check valve

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Fan inlet and diffuser housing

*
Air cycle machine (ACM)

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Second stage turbine bypass valve

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Condenser/reheater.

All of the components in the left and right packs are the same except for five of the ducts that connect the pack components together. The orientation of the components in one pack is a mirror image of the other. The airflow is also a mirror image. The difference in the ducts lets the inlets to the dual heat exchangers always be on the top and the outlets on the bottom.
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BOEING PROPRIETARY -Copyright # -Unpublished Work -See title page for details. 

AIR CONDITIONING -PACK CLG AND MIX MANIFOLD TEMP CTRL -COMPONENT LOCATIONS

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AIR CONDITIONING -PACK CLG AND MIX MANIFOLD TEMP CTRL -RAM AIR -COMPONENT LOCATIONS

Component Locations
All of the ram air components of the left and right air conditioning packs are in the underwing fuselage area. Each pack has these ram air components:
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Ram air inlet door (two sections)

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Ram air inlet door actuator (not shown)

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Ram air inlet duct

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Ram air inlet duct clean out panel

*
Fan bypass check valve

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Fan inlet and diffuser housing

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Fan section of the ACM

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Ram air exhaust housing.

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