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 ground of system by pressing in on ground detector
8.
Adjust generator voltage to 120
button (13) and observe the ground lights (4). If an
volts.
accidental ground is present, one of the lights will
9. Move shore power supply switch (37)
increase its brilliance and the other will darken. If the
to OFF.
(-) light is brightest, the ground exists on the negative
10. Deenergize shore power source
leg of the system. If the (+) is light is brightest, the
and disconnect shore power cable.
ground exists on the positive leg of the system. To
isolate a ground indicated on ground lights (4), proceed
NOTE
as follows:
After shifting to or from shore power,
1. Operate the distribution switches (18
check that all electrical equipment
through 37) one at a time to OFF and ON. If the ground
has restarted. Restart equipment as
lights return to normal brilliance when a switch is in the
necessary.
OFF position, yet indicates an accidental ground when
that switch is at the ON position, the ground is in the
(i) To secure one generator from parallel
system supplied by that switch. The ground may be
operation.
isolated further' by placing switch of the grounded circuit
1. Check ammeters (14 and 41) to see
in ON position, then opening switches on branch
that load indications are the same on both generators.
circuits, pulling fuses, or opening line switches.
Adjust the rheostat to obtain this condition if necessary.
2. If the ground is not located by
2. Open the generator equalizer switch
operation of the distribution switches in 1 above, shift
(39).
power source from one generator to the other and
3. Remove the load from the generator
repeat the test. If ground indication disappears, the
to be secured by turning rheostat clockwise slowly until
defect lies in circuit of generator initially in use.
3. If power is being supplied from shore
it is carrying 75 percent of load. Turn the circuit handle
when ground is detected, shift the load to one of the tug
to TRIP position to open the circuit breaker of the
generators and disconnect shore power. Repeat the test.
generator to be secured.
If the ground indication disappears after the shore power
4. Adjust the voltage to 115 volts.
cable has been disconnected, the ground is not in the
5.
Open the generator disconnect
tug' electrical system.
s
switch (16 or 38) for the generator to be secured.
6. Secure the generator set (para. 2-
2-18. Engine Cooling System Operation
a. General. The cooling system for the propulsion
(j) The ground detector system consists of
and auxiliary set engines is divided into two subsystems;
two clear lens lights connected in series across the main
fresh water, and raw water. The fresh water system
distribution bus bars of the control panel. The ground
circulates through each engine block, and transfers heat
detector button (13, fig. 2-5) connected in series
from the engine to its heat exchanger. The raw water
between the ground lights (4) on one end, and
system circulates through all heat exchangers and
connected to ground on the control panel frame, is a
removes the heat from the fresh water. See figure 2-23.
part of the ground detector system. The ground detector
lights (4) burn at half brilliance at all times the tugs
electrical system is energized. Test for accidental
2-46
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