table 6-1. Neutral polarity, where it exists, is
identified by the white conductor.
Isometric Wiring Diagram
An isometric wiring diagram is supplied for each
shipboard electrical system. If the system is not too
large, the diagram will be on one blueprint while larger
systems may require several prints. An isometric wiring
diagram shows the ship’s decks arranged in tiers. It
shows bulkheads and compartments, a marked center-
line, frame numbers usually every five frames, and the
outer edge of each deck in the general outline of the ship.
It shows all athwartship lines at an angle of 30 degrees
to the centerline. Cables running from one deck to
another are drawn as lines at right angles to the center-
line. A single line represents a cable regardless of the
number of conductors. The various electrical fixtures
are identified by a symbol number and their general
location is shown. Therefore, the isometric wiring dia-
gram shows a rough picture of the entire circuit layout.
"Figure 6-2 (four pages at the end of this
chapter) shows an isometric diagram of a
s e c t i o n o f t h e s h i p ' s s e r v i c e a n d
emergency lighting system for a DLG." This
figure shows the forward quarter of the decks con-
cerned, whereas the actual blueprint will show the entire
decks. Note the reference to another isometric diagram
at the top of the figure. It shows that the diagram of the
complete lighting system for this ship required two
blueprints. All electrical fittings and fixtures shown on
the isometric wiring diagram are identified by a symbol
number as stated previously. The symbol number is
taken from the Standard Electrical Symbol List,
NAVSHIPS 0960-000-4000. This publication contains
a complete list of standard symbol numbers for the
various standard electrical fixtures and fittings for ship-
board applications. For example, look at the distribution
box symbol 615 located on the second platform star-
board at frame 19 (fig. 6-2). It is identified in
NAVSHIPS 0960-000-4000 as a type D-62A four-
circuit distribution box with switches and midget fuses.
Its federal stock number is 6110-152-0262.
Cables shown on the isometric wiring diagram are
identified by the cable marking system described earlier
in this chapter. In addition, cable sizes are shown in
circular mils and number of conductors. Letters show
the number of conductors in a cable; S for one-, D for
Table 6-1.—Color Code for Power and Lighting Cable Conductors
System
3-phase ac
No. of
Conductors
in Cable
3
2
2
2
Phase
of
Polarity
A
B
C
AB
BC
AC
Color
Code
Black
White
Red
A, black
B, white
B, white
C, black
A, black
C, white
3-wire dc
3
2
2
2
+
+/-
+ and +/-
+/- and -
+ and -
Black
White
Red
+, black
+/-, white
+/-, white
-, black
+, black
-, white
2-wire dc
2
+
Black
White
6-4
