3. Operation
A. Functional Description
(1)
Passenger cabin air supply and passenger cabin temperatures may be monitored by the temperature indicator on the forward overhead panel. The temperature is indicated according to the position of the AIR TEMP selector. The temperature indicating system aids in air conditioning operation during manual control and gives an early indication of what is taking place in the air conditioning system. During normal operation with both air cycle systems operating, SUPPLY DUCT temperature is a result of the position of both mix valves. With one air cycle system operating and the mix valve in full COLD, the supply duct temperature indicated is approximately the same as the system outlet temperature. Air from the left system enters the distribution duct a greater distance from the duct temperature bulb than air from the right system. As a result environmental conditions will affect the supply duct temperature reading more during left air cycle system operation than during right system operation.
(2)
The AIR TEMP selector switch permits switching between SUPPLY DUCT and PASS CABIN temperature. As there is no off position, the selector should be left in the SUPPLY DUCT position except when checking other temperatures. A sudden change in supply duct temperature indicates a possible malfunction in one or both air cycle systems.
B. Control
(1)
Provide electrical power.
(2)
Position AIR TEMP selector to area of interest and observe TEMP indicator.
(3)
Remove electrical power if no longer required.
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Jun 20/85 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 21-62-0 Page 1
Temperature Indicating System Component Location 5C8
21-62-0 Figure 1 (Sheet 1) Jun 20/85
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
551 Temperature Indicating System Component Location
May 1/75 Figure 1 (Sheet 2) 21-62-0
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CABIN AIR SUPPLY TEMPERATURE BULB - REMOVAL/INSTALLATION
1. General
A. The cabin supply duct temperature bulb is located on the main distribution manifold. (See figure 401.) Access to the bulb is through the aft bulkhead of the forward cargo compartment.
2. Prepare for Removal of Duct Temperature Bulb
A. Open TEMP IND circuit breaker on P6-2 circuit breaker panel.
B. Remove center portion of forward cargo compartment aft bulkhead to gain access to main distribution manifold.
C. On airplanes with protective shield, remove three screws securing shield to main distribution manifold.
3. Remove Duct Temperature Bulb
A. Disconnect electrical connector from duct temperature bulb. (See figure 401.)
B. Unscrew temperature bulb from duct receptacle and remove temperature bulb and gasket.
4. Install Duct Temperature Bulb
A. Place O-ring gasket on temperature bulb, screw bulb into duct receptacle and tighten. (See figure 401.)
NOTE: When new bulb is installed, remove asbestos type gasket supplied with bulb and replace with O-ring type.
B. Connect electrical connector to duct temperature bulb.
C. Connect external electrical power.
D. Close TEMP IND circuit breaker on load control center circuit breaker panel P6-4.
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Nov 15/68 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 21-62-11 Page 401
Cabin Air Supply Temperature Bulb Installation 511
21-62-11 Figure 401 Nov 15/68
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E. Move air temperature selector to SUPPLY DUCT and check that a positive reading registers on the temperature indicator.
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