168
Section 2 Installation
Copyright Goodheart-Willcox Co., Inc.
• If different voltages and phases may be
required within the same structure, addi-
tional services are allowed.
Number of Service
Entrance Conductor Sets
Since the basic rule is that each building will
have only one service drop or service lateral,
the usual service installation will have only one
set of service entrance conductors. Necessary
exceptions include multiple occupancies, such
as two-family homes, apartment buildings, and
commercial establishments with several offi ces
or stores. These occupancies may have any
number of service entrance sets tapped from
a single service supply, Figure 10-5. The NEC
permits a maximum of six disconnects from any
single service drop or service lateral. Figure 10-6
illustrates a possible installation of this nature.
Regardless of the number of service drops,
laterals, or sets of service entrance conductors,
the service should be carefully planned so that
the service entrance conductors are not routed
through the building interior unless encased
in concrete. The service entrance conductors
should also terminate at the disconnect outside
or close to where they enter the structure. See
Figure 10-7.
Service Load
For new single-family dwellings, the NEC
requires at least a 100 A service. For homes
with electrical heating systems or where future
expansion is likely, 150 A or 200 A service is
preferred. However, to be sure that the service
Single service
drop
Service drop
continued along
exterior of building
Common metering
equipment
Individual disconnects
located in each occupancy
Service entrance conductors
installed on building
exterior to each occupancy
Figure 10-5. Multiple occupancies may have any number of service entrance conductors tapped from a service
drop or service lateral.