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 TM 55-1905-223-10
1-30. Electrical System The electrical system distributes 240 Vac, 120 Vac, and emergency power
.
throughout the ship. 240 Vac, 3-phase, 60 Hz power is received from the power generation system ship's
service diesel generator sets and routed via the main ship's service switchboard and the emergency switch
board via the emergency switchboard bus tie, to selected equipment panels. 240 Vac power is also provided
by the main switchboard to a stepdown isolation transformer providing power to the 120 Vac distribution panel.
This panel distributes 120 Vac power to a quarters heating panel, galley power panel, and lighting panels.
Essential equipment and systems ties into the emergency switchboard normally receive power from the
emergency switchboard via the bus tie. When 240 Vac power is lost, these equipments and systems receive
240 Vac power from the emergency diesel generator set through the emergency switchboard. The emergency
switchboard also provides 120 Vac power through stepdown transformers to a 120 Vac distribution panel. This
panel provides 120 Vac power to the emergency switchboard battery charger, which charges the emergency
switchboard 24 Vdc batteries, providing voltage to the 24 Vdc distribution panel. This panel provides 24 Vdc
power to those systems required to maintain propulsion control, and communication, when tied to shore power
through the shore power box, power distribution is the same as provided for primary power. No components
are grounded to the hull. All electrical leads go from a panel to the equipment energized and back to the panel.
1-31. Fresh Water Piping System The fresh water piping system provides cold and hot potable water
.
throughout the LCU. System control is maintained through a combination of valves as shown in FIGURE 1-39.
The system consists of two reverse osmosis watermakers, two fresh water (FW) pumps and pressure switches,
a pressure tank, hot water heater, and fresh water tank level indicator transmitters. Also included is a hot water
booster pump and hot water booster heater for the Gaylord Hood. The FW tanks are filled and vented through
fill and vent connections on the main weather deck. Each FW tank has a drain to the bilge. In addition to the
potable water system, cold fresh water (CFW) is supplied to the fresh water cooling piping system.
a. Reverse Osmosis Watermaker.s Two reverse osmosis (RO) watermakers take seawater from the sea
chest and, through the reverse osmosis process, separate brine and foreign matter from the seawater and
supply fresh water to the port and starboard fresh water tanks. Brine is discharged overboard from the RO
watermakers. Power is supplied to the fresh watermakers from the AUX MCHRY MCC and can be started and
stopped from the engine room console and at the watermaker units.
b. FW Pumps No. 1 and No. . Two FW pumps draw CFW from the port and starboard FW tanks and
2
route the CFW under pressure to the hydropneumatic pressure tank, which maintains CFW pressure throughout
the system. Power for the pumps is supplied from the main switchboard 240 Vac distribution, and controlled by
start and stop pushbuttons on the engine room console and by pressure switches. One pump (main) is on line
and the other (standby) is in reserve.
c. Pressure Switche. Each FW pump pressure switch automatically turns on its respective FW pump
s
when pressure drops below to the cut-in setpoint (pump 1-35 psi, pump 2-30 psi). Each FW pump pressure
switch automatically turns off its respective FW pump when pressure exceeds 60 psi.
d. Pressure Tank The hydropneumatic tank maintains CFW supply pressure for the system.
.
Pressurized CFW is supplied from the pressure tank to various points throughout the ship and to the hot water
heater.
Change 3
1-108
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