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747-400
MAINTENANCE MANUAL
4. Waste Tank Drain Heaters
________________________
A. Formation of ice on the waste tank drain tubes is prevented by heater blankets which enclose the tubes. The heater blankets are installed on the drain tubes between the waste tanks and the drain valves and a separate blanket is installed on each drain valve. A heater blanket is also installed on the drain tube where it meets the waste tank service panel.
B. Formation of ice in the toilet drain servicing cap is prevented by a gasket-type electrical heating element placed between the drain cap flange and the service panel structure. This is a low wattage heater and has no thermostat. It is on as long as power is available. The four waste tank flush fittings at the service panel are enclosed by heaters with thermostats built into them.
5. Operation (Figs. 2 and 3)
_________
A. Functional Description
WARNING: OPEN DRAIN MAST HEATER CIRCUIT BREAKERS ON P414 PANEL WITH
_______ EXTERNAL POWER IN GROUND SERVICE POSITION TO PREVENT BURNS TO PERSONNEL OR OVERHEATING DRAIN MASTS.
(1) 115 volts ac is supplied to the potable water line heaters, waste water drain heaters, and toilet service panel heaters. The heat system is on whenever airplane ac power is supplied. The drain mast, waste drain, and water supply line heater circuit breakers on the P414 Left Power Distribution Center provide circuit protection. Thermostats turn each heater on when the temperature drops to a threshhold level. When the airplane is on the ground, the drain mast heaters are switched from 115 to 42.5 volts ac.
B. Control
(1) Operation of the water and waste line heaters is automatic. No control functions are exercised.
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747-400
MAINTENANCE MANUAL
FOR LOCATIONS OF DRAIN HEATERS P415 RIGHT POWER DISTRIBUTION CENTER
Drain Heaters Simplified Schematic Figure 2
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747-400
MAINTENANCE MANUAL
NOTE: REFER TO WIRING DIAGRAM MANUAL FOR LOCATIONS OF WATER LINE HEATERS
Water Supply Line Heaters Simplified Schematic Figure 3
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747-400 MAINTENANCE MANUAL
WATER LINE AND WASTE DRAIN HEATERS - ADJUSTMENT/TEST
____________________________________________________
1. General_______
A. This task is an operational test of the water supply and drain heaters.
(1) These tests are included in the operational test and can be done together or independently:
(a)
Drain Mast Heaters Ground Mode Test
(b)
Drain Mast Heaters Air Mode Test
(c)
Ribbon Heaters Test
(d)
Heated Supply Hose Test
(e)
In-Line Heaters Test
(f)
Test of the Blanket Heater for the Waste Tank Drain Line
(g)
Transfer Relay Air Mode Test
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本文鏈接地址：747-400 AMM 飛機維護手冊 防冰和排雨 ICE AND RAIN PROTECTION(81)
