TYPES OF RECEPTACLES
system as possible with respect to the location of the
fault.
On the older ships with single 125-volt, 10-ampere,
The attainment of selective tripping requires careful
single-phase ac (or two-wire de), stub-type watertight
coordination of time-current characteristics for the
receptacles are used for all applications except for
different groups of circuit breakers. For example, if the
electric shavers and some electronic applications. For
system shown in figure 2-59 is operating split plant (bus
electric shavers and some electronic applications,
ties open) and if the time-current characteristics of the
double 125-volt, 15-ampere, single-phase ac (or
ACB feeder breaker and the ACB generator breaker
two-wire dc) bladed-type receptacles are used
were interchanged, a fault at B with overcurrent would
trip generator 1SG off the line but would leave the feeder
On new ships, general-purpose grounded
connected to the switchboard. This action would
receptacles are provided as follows:
disconnect power to all equipment supplied by
1. Double 125-volt, 15-ampere, single-phase ac (or
switchboard 1S and also would not isolate the faulty
two-wire dc) bladed-type receptacles are used
section. Therefore, no unauthorized changes should be
for all below-deck applications.
made to circuit breaker trip settings because these
2. Single 125-volt, 15-ampere, single-phase ac (or
changes may completely disrupt the scheme of
protection based on selective tripping.
two-wire de) watertight bladed-type receptacles
are installed on radar platforms and open bridges
System protection by selective tripping of circuit
for use of electronic test equipment.
breakers cannot be provided to all types of naval ships
3. Single 125-volt, 10-ampere, single-phase ac (or
or for all circuits. For example, dc distribution systems
two-wire dc) stub-type submersible receptacles
in older ships and all lighting circuits use fuses to a great
are used topside and for applications where a
extent. Time delay can be incorporated only to the
watertight receptacle is require&except on radar
extent that is permitted by the characteristics of the
platforms and open bridges.
fuses. The use of progressively large fuse sizes from the
load to the generator provide some degree of selectivity
RECEPTACLE LOCATION
for overload or limited fault protection.
Receptacles must be spaced to permit the use of
GROUNDED RECEPTACLES
portable tools at anyplace on the ship without requiring
more than 50 feet of flexible cable between a tool and
Grounded receptacles are installed aboard naval
receptacle. Receptacles installed for specific
vessels to ensure that grounded plugs, portable cables,
applications, such as radiant heaters, are included in the
and portable electrical tools are grounded to the ship's
receptacle spacing to meet the 50-foot limit. They may
structure when they are in use. The ground wire
be considered as available for portable tools.
prevents the occurrence of dangerous potentials
If additional receptacles are required to meet the
between the tool or equipment housing and the ship's
50-foot limit, make sure that added receptacles don't
structure. This protects the user from fatal shock.
result in overloading the circuits. In some ships the
The grounded receptacles most widely used aboard
receptacles are on an isolated circuit as an additional
naval vessels have metal enclosures internally
means of preventing fatal shocks.
connected to the ground terminal of the receptacle.
Grounding the enclosures will ground the grounded
RECEPTACLE TESTING
terminal. Grounded receptacles with plastic enclosures
are also used aboard some vessels. In some types, the
The routine ground continuity test of each installed
grounded terminal is connected to ground through a
receptacle is required by PMS. Before a receptacle is
conductor. In later types, the grounding ferrules are
ground tested, it must be de-energized, safety tagged,
molded within the mounting. The ground wire is also
and checked for voltage. This safety precaution will
molded within the bottom of the box and connects the
protect you and the test equipment.
grounding terminal to the metal insert. The
In one method of testing, you connect one test lead
cross-sectional area of the conductor used to connect the
of an ohmmeter or multimeter to the ground lead of a
grounded terminal to ground must be at least the same
dummy plug of the receptacles to be tested. The power
size or greater than that of the conductors that supply a
prongs of this plug are to be left unconnected. Insert the
receptacle.
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