Laboratories (UL) tests various electrical fixtures
and devices to determine if they meet minimum
specification and safety requirements as set up by
UL. Those fixtures and devices that are approved
may then bear UL labels.
In the SEABEEs, utility drawings (both
mechanical and electrical) are thoroughly reviewed
before an excavation (or digging) permit is granted
and issued to the project subcontractor. Such
action minimizes the hazards to personnel and
underground structures during the construction
process. All of the minor design changes and field
adjustments must be noted and reflected on
as-built and working drawings. Therefore, close
coordination and cooperation must develop
within and among all of the parties involved in
the project to maintain periodic checks on
red-lined prints so that information can be
compared and verified as up to date.
The conventions used on the electrical plan are
SYMBOLS that indicate the general layout, units,
related equipment, fixtures and fittings, and
routing and interconnection of various electrical
wiring. The most common types of symbols
used in electrical drawings are shown in
figure 9-23. To see additional or special symbols,
refer to the appendix section of this book and/or
to ANSI Y32.9.
To draw in electrical symbols in an electrical
drawing, as in drawing a mechanical plan, it is
best to use templates. For example, a wiring
symbol is generally drawn as a single line but with
slanting tick marks to indicate the number of
wires in an electrical circuit.
Exterior distribution lines (or network) deliver
electrical power from the source (generating
station or transmission substation) to various
points of use. Figure 9-24 shows a typical layout,
extracted from NAVFAC P-437, Facilities
Harming Guide, of an exterior electrical network
of buildings for a 100-man camp. This layout, in
condensed form, shows a site plan of the camp
area with facilities and the location of the
electrical component system. Included in the
electrical plan is a list of facilities (upper right-
hand corner of fig. 9-24) that describes the
corresponding item symbol, facility number, and
quantity. An electrical load data table is also
included in the drawing.
As an EA, you will be called upon to trace,
modify, revise, and even review the workability
of the drawing. It is therefore to your advantage
not only to study and become familiar with the
electrical plans, but also to gain a working
knowledge of how the system works. NAVFAC
P-437 offers a wide variety of plans, drawings,
and applications for the Advanced Base Func-
tional Component (ABFC) System for use in
As we mentioned earlier, the electrical
information on exterior electrical distribution is
generally shown in the regular site or plot plan.
The INTERIOR ELECTRICAL LAYOUT, how-
ever, is, for small buildings, drawn into a print
made from the floor plan. On larger projects,
additional separate drawing sheets are necessary
to accommodate detailed information needed to
meet construction requirements.
Figure 9-25 shows an electrical layout of a
typical public works shop. Once again, note that
the electrical information is superimposed on an
outline taken from an architectural floor plan. In
addition to the list of assemblies and electrical
load table, a wiring diagram and panel schedule
of a 225-A, three-phase circuit breaker is drawn.
The underground service entrance (item 10 on the
list of assemblies) delivers a four-wire, 120/208-V
power into the building. Lighting circuits use a
three-wire, No. 12 AWG (TW).
The following basic steps are suggested to
guide you in the development of an interior
1. Show the location of the service panel and
its rating in amps.
2. Show all of the wall and ceiling outlets.
3. Show all of the special-purpose outlets,
such as telephones, communications, doorbells,
and so forth.
4. Show all of the switches and their outlet
5. Show convenience outlets.
6. If required,
complete a schedule of
electrical fixtures, symbols, legends, and notes
necessary to clarify any special requirements in
the drawing that are not stipulated in the
The steps suggested above can be put to
practice in the next chapter following mastery of
civil and architectural drawings.