Section 110. 31(D) covers enclosed
equipment that is accessible to unqualified people. The first part is similar to the
last sentence in 110. 31(B)( 1) that pertains
to dry-type transformers. Ventilating or
similar openings in equipment shall be
designed so that foreign objects inserted
through these openings are deflected
from energized parts.
The next sentence states, where
exposed to physical damage from
vehicular traffic, suitable guards shall
be provided. Since this section is not
divided into indoor and outdoor locations, this provision applies to both types
of locations. Vehicles inside industrial
plants are not uncommon. Therefore,
electrical equipment must be protected
from physical damage whether installed
indoors or outdoors.
The next provision is specifically for
outdoor equipment rated over 1,000V.
Equipment located outdoors that is
accessible to unqualified people shall be
designed so that exposed nuts or bolts
cannot be readily removed, permitting
access to live parts. While some provisions in Part III have a similar provision
in Part II for equipment rated 1,000V,
nominal, or less, there is no requirement
in Part II to prohibit nuts and bolts from
being readily removed. Where equipment is accessible to unqualified people
and the bottom of the enclosure is less
than 8 feet above the floor or grade level,
the enclosure door or hinged cover shall
be kept locked (see Figure 3).
Section 110. 31(D) continues by requir-
ing doors and covers of enclosures used
solely as pull boxes, splice boxes or junc-
tion boxes to be locked, bolted or screwed
on. Underground box covers that weigh
more than 100 pounds shall be consid-
ered as meeting this requirement. The
NEC mentions manhole access covers
five times. A manhole access cover does
not have to be locked, bolted or screwed
on as long as it weighs more than 100
pounds (see Figure 4).
Working space requirements for equip-
ment over 1,000V are in 110. 32. Sufficient
space shall be provided and maintained
about electrical equipment to permit ready
and safe operation and maintenance of
such equipment. Where energized parts
are exposed, the minimum clear work
space shall not be less than 6½ feet high
(measured vertically from the floor or
platform) or not less than 3 feet wide
(measured parallel to the equipment).
This section states the clear work
space shall be at least 6½ feet high or not
less than 3 feet wide. This is odd since
110. 26 (for equipment rated 1,000V, nom-
inal, or less) requires a minimum work
space height and a minimum work space
width. In my opinion, the clear work
space shall be at least 6½ feet high and
not less than 3 feet wide. Section 110. 32
continues by requiring the work space
depth to comply with 110. 34(A). The last
sentence in 110. 32 for equipment over
1,000V is just like the last sentence in
110. 26(A)( 3) for equipment rated 1,000V,
nominal, or less. In all cases, the work
space shall permit at least a 90-degree
opening of doors or hinged panels.
Next month’s column continues
the discussion of electrical installation
MILLER, owner of Lighthouse Educational Services, teaches custom-tailored seminars
on the National Electrical Code and NFPA 70E. He is the author of “Illustrated Guide to
the National Electrical Code” and “Electrician’s Exam Prep Manual.” He can be reached at
615.333.3336 and Electric Writer@ymail.com. Connect with Charles R. Miller on LinkedIn.
FIGURE 4 MANHOLE ACCESS COVER
Doors and covers of enclosures used solely as pull boxes, splice boxes, or junction
boxes shall be locked, bolted or screwed on [ 110. 31(D)].
Underground box covers that weigh more than 100 pounds shall be considered as
meeting the requirements to lock, bolt or screw on doors and covers of enclosures
[ 110. 31(D)].
This manhole access cover weighs more than 100 pounds.
Continued from page 60