nect switch is one example of a cutout
box. Disconnecting means also is defined
in Article 551, but the definition in 551.2
applies to recreational vehicles and RV
parks only. In Article 551, disconnecting means is the necessary equipment
usually consisting of a circuit breaker or
switch and fuses, and their accessories,
located near the supply conductors point
of entrance in a recreational vehicle and
intended to constitute the means of cutoff for the supply to that RV.
As previously mentioned, requirements for disconnecting means are
throughout the Code; Article 110 contains
several of these requirements. The first,
located in 110.22(A), states each disconnecting means shall be legibly marked
to indicate its purpose. Because of the
definition of a disconnecting means,
this provision applies to many different
types of equipment, such as fused and
nonfused disconnect switches, circuit
breakers in panelboards and switchgear
(see Figure 3).
The provision in 110.22(A) also states
that, if the purpose of the disconnecting means is obvious because of where
it is located, it is not required to mark
the purpose of the disconnecting means.
For example, a safety switch or disconnect is supplying power to a rooftop air
conditioning unit and is mounted on the
unit. Since it is obvious the disconnect is
supplying power to the air conditioning
unit, marking this disconnecting means
to indicate its purpose is not required
(see Figure 4).
The last sentence in 110.22(A)
requires the marking to be of sufficient
durability to withstand the environment.
For example, two disconnect switches
are located outside a building. The dis-
FIGURE 2 PANELBOARD
Article 100 defines the term “panelboard” as a single panel or group of panel units
designed for assembly in the form of a single panel, including buses and automatic
overcurrent devices, and equipped with or without switches for the control of light,
heat, or power circuits; designed to be placed in a cabinet or cutout box placed in or
against a wall, partition, or other support; and accessible only from the front.
In the field, the term “panelboard” usually means the complete unit that includes the
panelboard and the cabinet or cutout box.
Main lug (MLO)
A cabinet is an enclosure that is designed for either surface-mounting or flush-mounting
and is provided with a frame, mat or trim in which a swinging door or doors are or can be
hung (Article 100).
Main breaker (MB)
FIGURE 3 IDENTIFICATION
Each disconnecting means shall be legibly marked to indicate its purpose [110.22(A)].
In accordance with 408.4(A), every circuit and circuit modification shall be legibly identified
as to its clear, evident and specific purpose or use. The identification shall include an
approved degree of detail that allows each circuit to be distinguished from all others.