5) The backup-temperature-control card causes the air cooling pack to go to the cool mode (the ram air doors and the temperature control valve open).
(i) A pack overheat condition occurs when the pack discharge temperature is more than 190°F (88°C). At 190°F (88°C), the pack overheat switch closes and sends an overheat signal to the flow control card. The flow control card then latches in the overheat position and causes the following conditions to occur: 1) The backup temperature control card causes the pack to go
the the full cold mode (the ram air doors fully open and
the temperature control valve closes).
2) The AUTO/MANUAL relays are not energized (this prevents control of the air cooling pack by the automatic-pack-temperature controller).
3) The INOP light, on the P5 panel, comes on. 4) The advisory messages L (R) PACK TEMP show on the EICAS display.
(j)
The air cooling packs operate as usual when the temperature switches are open and the RESET switch, on the P5 panel, is pushed.
(4)
The Pack Temperature Control (Fig. 13, 14, 15, 16)
(a)
The air-cooling-pack-outlet temperature is controlled by the automatic-pack-temperature controllers, the standby-pack-temperature controller, or the backup-temperature-control cards (Ref 21-53-00). Each component controls the air cooling packs for a different temperature mode. The temperature mode is controlled by the position of the L and R PACK selectors, on the P5 panel (the L and R PACK selectors can be in different temperature modes at the same time). The temperature modes are AUTO, STBY-N, STBY-W, STBY-C, and OFF.
(b)
The AUTO mode.
1) In the AUTO mode, the automatic-pack-temperature-controllers control the air cooling packs. 115v ac power is always supplied to each controller. When the L or R PACK selector is in AUTO, 28v dc is supplied to energize the left or right AUTO/MANUAL relays (the ground is supplied in the flow control cards when an overheat condition does not occur). The controller sends signals through the AUTO/MANUAL relays to control the position of the ram air doors and the temperature control valve. Also, because the low-limit-control valve relay is not energized, the controller can send signals to the low-limit-control valve.
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L PACK TEMP CONTROLLERLEFT SYSTEM SHOWN, RIGHT SYSTEM EQUIVALENTPack Auto Control OperationFigure 13 (Sheet 1)
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Pack Auto Control OperationFigure 13 (Sheet 2)
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LEFT PACK TEMPERATURE CONTROLLER
TEMPERATURE SENSOR 1
NOTES:
1 INPUT INVERTED - GROUNDED
INPUT = LOGIC "1"
LEFT SYSTEM SHOWN, RIGHT SYSTEM SIMILAR
Pack Auto Control Protection Schematic
Figure 14
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