FIGURE 2 WORKING SPACE—CONDITION 2
The minimum working space depth for this electrical equipment is 3 feet, 6 inches.
The second condition under Table 110.26(A)( 1) is where exposed live parts are on one side
of the working space and grounded parts are on the other side.
Concrete, brick or tile walls shall be considered grounded.
space depth for the 480V switchboard
in this installation is 4 feet (see Figure 3).
The working space depth for equipment operating at 600V, nominal, or
less to ground—and likely to require
examination, adjustment, servicing or
maintenance while energized—shall
not be less than the minimum clear
distances in Table 110.26(A)( 1) unless
meeting 110.26(A)( 1)(a), (A)( 1)(b) or
(A)( 1)(c) requirements.
The first requirement pertains to
dead-front assemblies, defined by Article
100 as without having live parts exposed
to a person on the equipment’s operating
side. The minimum clear working space
distances are not required in the back or
sides of assemblies, such as dead-front
switchboards, switchgear or motor control centers, where all connections and
renewable or adjustable parts, such as
fuses or switches, are accessible from
locations other than the back or sides
For example, a 480Y/277V, three-
phase, 4-wire switchboard will be
installed in an electrical room. A trans-
former is on the left side, and a panelboard
is on the other side of the transformer.
Another panelboard is on the right side
of the switchboard. No connections or
renewable/adjustable parts are accessible
from the sides or back. Working space is
not required for this switchboard’s back
or the sides (see Figure 4).
Sometimes rear access is needed at
the back of enclosed electrical equipment. If it is needed for equipment
operating at 600V, nominal, or less to
ground and the equipment is likely to
require examination, adjustment, servicing or maintenance while energized,
the working space depth shall comply
with Table 110.26(A)( 1). If rear access is
needed to work on nonelectrical parts,
a minimum working space distance is
required. In accordance with the last
sentence of 110.26(A)( 1)(a), if rear access
is required to work on nonelectrical parts
on the back of enclosed equipment, a
minimum horizontal working space of
30 inches shall be provided.
The second subsection under
110.26(A)( 1) pertains to low-voltage
equipment. Where all exposed live parts
operate at not greater than 30V rms, 42V
peak or 60V direct current (DC), smaller
working space shall be permitted but
only by special permission. The authority having jurisdiction (AHJ) will need
to provide more than verbal consent.
Article 100 defines “special permission”
as the AHJ’s written consent.
In a new building, when dead-front
switchboards, switchgear, panelboards
or motor control centers are located
across the aisle from each other, the
working space shall meet the minimum
clear distances for Condition 3. Under
the third condition, the minimum clear
distance for equipment having a nominal voltage to ground of 150V and less
is 3 feet, and the minimum clear distance for equipment having a nominal
voltage to ground of 151–600V is 4 feet.
In an existing building where electrical
equipment is being replaced, it may be
possible to reduce the minimum clear
FIGURE 3 WORKING SPACE—CONDITION 3
While the working space depth needed for the 208V switchboard is only 3 feet,
it is not enough for the 480V. The minimum working space depth for a 408V
switchboard is 4 feet.
The third condition under Table 110.26(A)( 1) is where there are exposed live parts on both
sides of the working space.
480V switchboard 208V switchboard
Exposed live parts on both
sides of the working space