ANSWER TO REVIEW QUESTION 5
The conventions used to show building connections on a sewerage plan are the same as those for plumbing
plans. (pa 3-10, f)
ANSWER TO REVIEW QUESTION 6
When wood walls are used, a concrete slab floor is favored as giving the best foundation for installation of
the intermittent siphon. (para 3-12, b)
Section IV. Electrical Distribution System
power from generating stations or transmission
3-15. DEFINITION
substations to various points of use. While the term
Electrical distribution is the delivery of power to
"distribution system" is normally used to designate
the using premises from the power plant or substation
the outside lines, they are frequently continued inside
through feeders and mains carried on poles or placed
the buildings to power outlets for electrical
underground.
equipment operation. These power outlets are
distinct from the usual lighting circuits or "interior
wiring."
3-16. NOMENCLATURE
The general term "power system" covers the
3-17. CONVENTIONS
large-capacity wiring installations and associated
equipment for the delivery of electrical energy from
The conventions used on the electrical utility
the point of generation to the point of use. The
plans are symbols that indicate the general layout,
power system is generally considered to be a
units, related equipment, and fixtures to be installed.
combination of two sections: the transmission system
Some common symbols you should be familiar with
and the distribution system. The difference between
are shown in figures 3-24 and 3-25. You will find
the two sections depends on the function of each as
additional symbols which are in common use listed in
defined below. At times, in small power systems, the
appendix A.
difference tends to disappear and the transmission
system merges with the distribution system, and the
3-18. MATERIALS AND FITTINGS
delivery network as a whole is referred to as the
"distribution system."
The principal difference between the wiring
materials for interior wiring and distribution lines is
A transmission
size. Larger sizes of wire are needed for greater
a. Transmission System.
system usually consists of step-up and step-down
current-carrying capacities. Spacing of wires and
transformer stations, transmission lines, and
insulation is increased to give protection needed
switching or substations. The system is used for the
where high voltages are used. With the increase of
transmission of bulk power to load centers and large
wire sizes, larger conduits, outlet or junction boxes,
industrial users beyond the economical service range
insulators, connectors, fuses, switches, and circuit
of the regular primary distribution lines.
breakers are needed. Tables 3-2 through 3-5 list the
dimensions and current-carrying capacity for the
b. Distribution System. A distribution system
most frequently used wire types and sizes. Sizes are
usually consists of primary distribution lines or
listed by American Wire Gauge (AWG) numbers.
networks, service transformer banks, and secondary
Current-carrying capacity is based on a maximum air
lines or networks. The system is used to deliver
temperature of 100 degrees F. If the maximum air
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