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Construction Electrician Basic - Electricity handbook for electricians | Next
Interior Wiring Systems |
Figure 5-6.—Meter socket and wiring.
Figure 5-5.—Service mast service entrance.
SERVICE DISCONNECTS
A weather head, also called a service head, as
shown in figure 5-5, is used with a raceway to provide
an exit for the conductors from the raceway. The
weather head is designed to prevent the entrance of rain
into the raceway. The conductor holes in the service
head are designed to reduce abrasion to the insulation.
Power delivered to the building may need to be
measured to determine how much power is used. When
this measurement is necessary, a watt-hour meter socket
(fig. 5-6) is installed in the service entrance circuit so
that a wattmeter may be included to record power
consumption. Article 230 of the NEC© covers the
service conductors and equipment for control and
protection of services and their installation
requirements.
The service entrance must provide a means of
disconnecting the service entrance conductors from the
interior building circuits.
The service disconnecting
means will be installed at a readily accessible location
either outside of a building or structure, or inside nearest
the point of entrance of the service conductors. A
service disconnect, or main switch, can be used to turn
off all interior power in case of a fire or other emergency
conditions. A disconnect switch is also useful when
work is to be performed on the panelboard or work is
done on two or more circuits at the same time.
Overcurrent protective devices are required for the
service conductors in conjunction with the service
disconnects.
Several types of service entrance disconnects are
permitted. One of these is in the form of a knife-blade
switch with one, two, or three blades, as needed, to open
5-3
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