INS-2 — Working Space, Access, Guarding, and Enclosures

Decide whether 110.26 applies

Section 110.26 addresses access and working space about electrical equipment to permit ready and safe operation and maintenance. The dimensional working-space rules in 110.26(A) apply to equipment operating at 600 V nominal or less to ground that is likely to require examination, adjustment, servicing, or maintenance while energized. This is an installation rule. It does not say that energized work is automatically justified, and it does not replace OSHA de-energization, lockout/tagout, PPE, or safe-work-practice requirements.

Start with equipment function and voltage to ground. A 120/240 V single-phase system is 120 V to ground in the ordinary grounded configuration, so its table row is not selected merely from 240 V line to line. Then identify the condition across the working space.

Depth, width, and height

Table 110.26(A)(1) gives minimum depth. For 0–150 V to ground, Conditions 1, 2, and 3 each require 3.0 ft. For 151–600 V to ground, the minimums are 3.0 ft for Condition 1, 3.5 ft for Condition 2, and 4.0 ft for Condition 3.

• Condition 1: exposed live parts on one side and no live or grounded parts on the other, or live parts on both sides effectively guarded by insulating material.
• Condition 2: exposed live parts on one side and grounded parts on the other. Concrete, brick, or tile walls are considered grounded for this condition.
• Condition 3: exposed live parts on both sides of the working space.

Under 110.26(A)(2), working-space width is the equipment width or 30 in., whichever is greater. The space need not be centered, but it must allow equipment doors or hinged panels to open at least 90 degrees. Width is not measured as 15 in. from each side of the equipment.

Under 110.26(A)(3), working-space height extends from grade, floor, or platform to 6.5 ft or the equipment height, whichever is greater. Other equipment associated with the electrical installation may extend no more than 6 in. beyond the front of the equipment. Each dimension is tested separately; adequate depth does not excuse inadequate width.

Example: assume a 480Y/277 V panelboard faces a concrete wall. Voltage to ground is 277 V, and the grounded wall makes this Condition 2. The minimum depth is 3.5 ft. If the panel is 24 in. wide, minimum working width is 30 in. The panel can sit within that width without being centered, provided access and 90-degree opening are maintained.

Keep the space usable

Section 110.26(B) prohibits using required working space for storage. When normally enclosed live parts are exposed for inspection or service, the working area must be suitably guarded. A floor marking can help operations, but paint does not cure a permanently obstructed Code space.

Section 110.26(D) requires illumination for working spaces about service equipment, switchboards, switchgear, panelboards, and motor control centers installed indoors. The intent is usable illumination, not merely a luminaire somewhere in the room. The NEC installation requirement should not be expanded into an invented lighting-level value where the section provides none.

At least one entrance of sufficient area must provide access to and egress from working space. Under 110.26(C)(2), equipment rated 1,200 A or more and over 6 ft wide that contains overcurrent devices, switching devices, or control devices generally requires an entrance at each end of the working space, at least 24 in. wide and 6.5 ft high, unless an exception applies. One exception permits a single entrance where the location allows a continuous and unobstructed way of egress; another uses doubled working-space depth.

Under 110.26(C)(3), where equipment rated 800 A or more contains overcurrent, switching, or control devices, a personnel door intended for entrance to and egress from the working space and located less than 25 ft from the nearest edge of that working space must open in the direction of egress and have listed panic hardware or listed fire-exit hardware. Do not merge the 800 A door rule with the 1,200 A large-equipment entrance rule.

Dedicated equipment space

For indoor switchboards, switchgear, panelboards, and motor control centers, 110.26(E)(1) reserves a dedicated zone equal to the equipment width and depth, extending from the floor to 6 ft above the equipment or to the structural ceiling, whichever is lower. Foreign piping, ducts, and leak-protection equipment generally cannot occupy that zone, subject to the stated allowances. The dedicated zone above equipment is different from the working space in front of equipment.

Accessibility and guarding

Article 100 distinguishes accessible from readily accessible. Readily accessible equipment can be reached quickly for operation, renewal, or inspection without tools, climbing over or removing obstacles, or resorting to portable ladders. Under 110.26(F), electrical equipment rooms or enclosures controlled by a lock are considered accessible to qualified persons. Locked does not necessarily mean inaccessible under the Code definition.

Section 110.27(A) requires live parts operating at 50 V or more to be guarded against accidental contact by approved cabinets or enclosures, a room or vault accessible only to qualified persons, suitable permanent partitions or screens, or elevation of at least 8 ft above the floor or working surface, as applicable. Entrances to rooms containing exposed live parts require conspicuous warning signs forbidding unqualified persons to enter. Enclosures and guards must also be protected from physical damage.

Finally, select enclosure types for the actual location under 110.28 and applicable equipment rules. Indoor, outdoor, rain, sleet, dust, corrosion, and submersion are different conditions. An enclosure type marking protects against specified exposures; it does not automatically make the equipment suitable for every condition or preserve its rating after unapproved openings. NEC placement, guarding, and enclosure rules establish the installation. OSHA governs how employees perform work around the resulting hazards.