68 ELECTRICALCONTRACTOR | FEB. 17 | WWW.ECMAG.COM
space. This is an important clarification
because, when electrical equipment is
located above a lay-in ceiling, a person
working on the equipment is usually on
a ladder or a lift.
For example, a 208V HVAC unit is
installed above a 2-foot-by-2-foot lay-in
ceiling. In front of and below the access
door to the HVAC unit is a full-size
2-foot-by-2-foot ceiling tile. The working space in front of the access door to
the HVAC unit is at least 3 feet, which
complies with the minimum required
dimension specified in Table 110.26(A)
( 1). The working space height in front
of the access door for this HVAC unit is
enough height to install the equipment.
Because the working space requirements
for this HVAC unit meets the requirements in 110.26(A)( 4), this installation is
permitted (see Figure 3).
Since the requirement in 110.26(A)
( 4) pertains to all equipment installed
above a lay-in ceiling operating at
1,000V, nominal or less to ground and
likely to require examination, adjust-
ment, service or maintenance while
energized, the specific requirement
for electrical enclosures for resistance
heating element-type duct heaters that
are mounted on duct systems is no lon-
ger needed. Therefore, 424.66(B) has
The second new subsection under
110.26(A) requires the high-voltage
equipment to be separated from the
space occupied by the low-voltage
equipment by a suitable partition, fence
or screen [110.26(A)( 5)]. This applies
where switches, cutouts or other equipment operating at 1,000V, nominal or
less are installed in a vault, room or
enclosure where there are exposed live
parts or exposed wiring operating over
Unlike other requirements in 110.26
that specify certain minimum dimensions, this requirement does not.
Where electrical equipment operating
at 1,000V, nominal or less is in the same
vault, room or enclosure as equipment
with exposed live parts or exposed wir-
ing operating over 1,000V, nominal, the
two types of equipment shall be effec-
tively separated from each other. In
this type of installation, it is not enough
for the separation to be by a certain
distance only. The high-voltage equip-
ment shall be effectively separated by
a suitable partition, fence or screen
from the space occupied by the low-
This requirement does not apply to
high-voltage equipment with no exposed
live parts or exposed wiring. It only
applies to electrical equipment where
there are exposed live parts or exposed
wiring operating over 1,000V, nominal.
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.
CODE IN FOCUS
FIGURE 3 DEPTH AND HEIGHT OF WORKING SPACE
The space in front of the enclosure of equipment located in a space with limited access shall comply with the depth requirements of
Table 110.26(A)( 1) [110.26(A)( 4)(d)].
Access door to 208V HVAC equipment
ArcFashand Shock Hazard
2-foot-by-2-foot lay-in ceiling The working space in front of this HVAC unit’s access door is at least 3 feet.
Both depth and height requirements are in 110.26(A)( 4)
(d). The maximum height of the working space shall be the
height necessary to install the equipment in the limited
space. A horizontal ceiling structural member or access panel
shall be permitted in this space.
The voltage to ground for this 208V HVAC equipment is 120V.
In accordance with Table 110.26(A)( 1), the minimum clear
distance in front of this equipment shall be at least 3 feet.