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Low limit valve (LLV)

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Ram air door actuator.

These components operate in sequence to keep the necessary air temperature from the pack. This temperature is called the integrated mix manifold temperature error (IMMTE) reference. The CTC uses the TBV for primary control of pack output air temperature. The LLV and the ram air door actuator operate if the TBV is full open and the CTC still must increase pack outlet temperature. This keeps the necessary ram air flow to a minimum.
The right CTC is the primary controller of the mix manifold temperature. The left CTC usually follows the right in this condition. This type of operation makes the left and right pack outlet temperatures stay within 10F (5.5C) of each other. If the right pack is off or is in an overtemperature condition, the left CTC takes control of the mix manifold temperature.
The left and right CTCs can also control pack outlet temperatures to different values if it is necessary for the flight deck to have more cooling than the mix manifold.
The CTC usually uses the economy cooling valve (ECV) to help keep the scheduled air flow through the pack when the airplane is at high altitudes and low pneumatic duct pressure (economy cooling mode). The valve can be used to bypass the ACM if the ACM fails (STBY COOLING mode).
Compressor Outlet Temperatures Control
The CTC usually uses the ram air part of the system to control air temperature at the compressor outlet. The CTC can adjust pack air flow to limit compressor outlet temperature or stop pack operation to give protection. The CTC controls compressor out temperature in these limits:
COMPRESSOR OUT TEMP F (C)  CTC RESPONSE 
< 25,000FT  > 25,000FT 
< 340 (171)  < 400 (204)  MODULATE RAM AIR DOORS FOR PACK OUT TEMP CTRL
之 340 (171) 之 400 (204)  RAM AIR DOORS FULL OPEN
之 355 (179) *[1] 之 415 (213) *[1]  REQUEST LOWER PRECOOLER OUT TEMP FROM ASCPC (250F, 121C)
之 355 (179) 之 415 (213)  DECREASE PACK FLOW (LOWEST VALUE之 SCHEDULE 4) 

EFFECTIVITY BEJ ALL  21-52-00 
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AIR CONDITIONING -PACK CLG AND MIX MANIFOLD TEMP CTRL -FUNCTIONAL DESCRIPTION -PACKS

COMPRESSOR OUT TEMP F (C)  CTC RESPONSE 
< 25,000FT  > 25,000FT
之 450(232) > 10 SEC 之 450(232) > 10 SEC  CLOSE FCV & LATCH PACK OFF *[2] 

*[1] SINGLE PACK OPERATION OR PACK FAILURE OR ACM FAILED. *[2] RESET WITH PACK SW OR AIR COND RESET SW
See the pack flow control section for more information about the pack flow schedules and control (SECTION 21-51).
See the air conditioning section for more information about the air conditioning reset switch (SECTION 21-00).
Condenser Inlet Temperatures Control
The CTC usually uses the LLV to prevent the formation of ice in the condenser. The CTC can adjust pack air flow to keep the condenser from freezing. The CTC always controls the condenser inlet temperature so that it does not go to a value less than 34F (1C).
Pack Outlet Temperatures Control
The CTC usually uses the TBV, ECV, and the ram air part of the system to control the pack outlet air temperature. The CTC can adjust pack air flow to limit pack outlet temperature or stop pack operation to give protection. The CTC controls pack outlet temperature within these limits:
EFFECTIVITY
BEJ ALL

PACK OUTLET TEMP F (C)  CTC RESPONSE 
< 160 (71)  MODULATE TBV & RAM AIR DOORS FOR PACK OUT TEMP CTRL
之 160 (71) < 180 (82)  MODULATE PACK TO FULL COLD: * AIR DOORS TOWARDS FULL OPEN * TBV TOWARDS FULL CLOSED
之 180 (82) *[1]  REQUEST LOWER PRECOOLER OUT TEMP FROM ASCPC (250F, 121C)
之 180 (82)  DECREASE PACK FLOW (LOWEST VALUE之 SCHEDULE 4)
之 190 (88) > 10 SEC  CLOSE FCV & LATCH PACK OFF *[2] 

*[1] SINGLE PACK OPERATION OR PACK FAILURE OR ACM FAILED *[2] RESET WITH PACK SW OR AIR COND RESET SW
To prevent ice in the mix manifold, the CTC controls the pack valves and ram air doors to keep the mix manifold outlet temperature to a value more than 35F (2C). If the temperature at the mix manifold outlet decreases to a value less than this level, the CTC increases pack outlet temperature.
See the pack flow control section for more information about the pack flow schedules and control (SECTION 21-51).
See the air conditioning section for more information about the air conditioning reset switch (SECTION 21-00).
Economy Cooling Mode
The CTC selects the economy cooling mode if the all of these conditions occur:
21-52-00

Page 43 D633W101-BEJ Sep 05/2003

AIR CONDITIONING -PACK CLG AND MIX MANIFOLD TEMP CTRL -FUNCTIONAL DESCRIPTION -PACKS

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