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A 747-400 MAINTENANCE MANUAL
 (2)  S 422-045Put the cartridge in the lavatory basin faucet.
 (3)  S 432-046Put the cartridge cap on the spigot button and tighten.
 (4)  S 862-047Open the shutoff valve for the water supply.
 (5)  S 792-048Do a check to make sure that the cartridge has no leaks.
 (6)  S 862-049Turn the water heater switch to the ON position.
 (7)  S 412-050Install the access panel for the sink cabinet.

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 ú ú 01 Page 208 ú Jun 10/94
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
 WATER HEATING - DESCRIPTION AND OPERATION
_________________________________________
 1.  General_______
 A.  The water heater provides hot water to the washbasin in the lavatory. The heater is installed in the water supply line to the washbasin hot water faucet in the lavatory.
 2.  Water Heater (Fig. 1)____________
 A.  The heater consists of a 3-pint tank with three 140-watt heating elements. The heater is equipped with an ON-OFF switch, an on-off indicator light, pressure relief valve, and two thermal switches. Normal cycling is controlled by a thermal switch which opens the circuit to the heating element when the temperature of approximately 125°F has been reached. The overheat switch opens at approximately 195°F to de-energize the heater circuit in event the heat cycle switch malfunctions. The light on the heater is illuminated when the ON-OFF switch and the overheat switch are both closed. A pressure relief valve will prevent system rupture in event the heating element is not de-energized by the heat cycle or overheat switches.
 B.  WATER HEATERS WITH THE TEMPERATURE SELECT SWITCH; A temperature select switch is on the bottom of the water heater. The temperature select switch adjusts the control thermostat to give water that can be heated to one of three temperature ranges. The ranges are, 101°F to 109°F (LOW), 111°F to 119°F (MED) and 121°F to 129°F (HIGH). If the control thermostat fails in the closed position, the overheat switch will cut power to the heater circuit when the temperature gets to approximately 170°F.
 C.  WATER HEATERS WITHOUT THE TEMPERATURE SELECT SWITCH; The water heater will automatically heat the water to the temperature of approximately 125°F. The control thermostat opens the heater circuit when the temperature goes above 125°F and closes when the temperature goes below 125°F. If the control thermostat does not open at 125°F, the overheat switch will cut power to the heater circuit when the temperature gets to approximately 195°F.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL

HOT WATER OUTPUT
WATER HEATER SEE A
WATER
INPUT

OVERHEAT ON-OFFSWITCH LIGHT
(COVER REMOVED) A-A
PRESSURE
A
RELIEF VALVE
HOT WATER OUTPUT
ELECTRICAL CONNECTOR
HEATER CONTROL SWITCH
A
HEATER CONTROL SWITCH
ON-OFF LIGHT
TEMPERATURE SELECT SWITCH
SEE B
WATER INPUT
WATER HEATER A
HIGH
MED
LOW
TEMPERATURE SELECT SWITCH B1
1WATER HEATERS WITH THE TEMPERATURE SELECT SWITCH Lavatory Water Heater - Component Location Figure 1
H06392
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