Table 3-9. Continued.
electrical service enters the building. Subfeeders and
hold the circuit In line during a momentary heavy
additional protective devices may be used for devices
ampere drain, yet cut out the circuit under short-
such as motors.
circuit conditions. As you know, the heavy ampere
demand normally occurs in motor circuits when the
(1) Fuses. The device for automatically
motor is started.
opening a circuit when the current rises beyond the
safety limit is technically called a cutout, but more
(2) Fuse boxes. As a general rule the
commonly called a fuse. All circuits and electrical
fusing of circuits is concentrated at centrally located
apparatus must be protected from short circuits or
fuse or distribution panel. These panel are normally
dangerous overcurrent conditions through correctly
located at the service-entrance switch in small
rated fuses. The cartridge type fuse is used for
buildings or installed in several power centers in
current rating above 30 amperes in interior wiring
large buildings. The number d service centers or fuse
systems. The plug or screw type fuse is satisfactory
boxes in the latter case would be determined by the
for incandescent lighting or heating appliance
connected power load.
circuits. On branch circuits, wherever motors are
connected, time-lag fuses should be used instead of
(3) Circuit breakers. A circuit breaker is
the standard plug or cartridge type fuse. These fuses
a protective switching device designed to open a
have self-compensating elements which maintain and
current-carrying circuit under over-
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