3.4 Dedicated Equipment Space, Guarding & Over-1000-Volt Installations
Key Takeaways
- NEC 110.26(E)(1)(a) requires the space equal to the equipment width and depth to be kept clear of foreign systems from the floor to a height of 6 feet above the equipment or to the structural ceiling, whichever is lower.
- Dedicated space protects against foreign systems such as piping and ducts; sprinkler protection is permitted for the dedicated space where the piping complies with the rule, and suspended ceilings with removable panels are not considered structural ceilings.
- NEC 110.27 requires live parts operating at 50 volts or more to be guarded by an approved enclosure, a room or vault under qualified supervision, a suitable permanent partition or screen, or elevation of 8 feet or more above the floor.
- NEC 110.30 through 110.34 apply to installations over 1000 volts nominal, with working-space depths from Table 110.34(A) and required entrance, guarding, and warning-sign rules.
- NEC 110.34(C) requires permanent and conspicuous warning signs reading DANGER — HIGH VOLTAGE — KEEP OUT at entrances to rooms and enclosures containing exposed live parts over 1000 volts.
Dedicated Space Is Not Working Space
Candidates routinely merge these two ideas. They are separate rules with separate geometry and separate purposes.
| Working space — 110.26(A) | Dedicated equipment space — 110.26(E) | |
|---|---|---|
| Purpose | Room for a person to work safely | Room for the equipment's own conduits and future access, free of foreign systems |
| Measured | Depth, width and height in front of the equipment | The footprint of the equipment, extending upward |
| Applies to | Equipment likely to be examined or serviced while energized | Switchboards, switchgear, panelboards, motor control centers |
| Excludes | Storage; requires clear access and egress | Foreign systems — piping, ducts, and equipment foreign to the electrical installation |
The Indoor Dedicated Space Rule — 110.26(E)(1)(a)
The space equal to the width and depth of the equipment and extending from the floor to a height of 1.8 m (6 ft) above the equipment or to the structural ceiling, whichever is lower, shall be dedicated to the electrical installation. No piping, ducts, leak protection apparatus, or other equipment foreign to the electrical installation shall be located in this zone.
Three points do most of the exam work:
- The dimension is 6 feet above the equipment, or the structural ceiling if that is lower. In a room with an 8-foot structural ceiling and a panel whose top is at 6 feet 6 inches, the dedicated space stops at the structural ceiling — 18 inches above the panel — not at 12 feet 6 inches.
- The zone is the width and depth of the equipment, projected straight up. It is a column above the gear, not a space in front of it.
- A suspended ceiling with removable panels is not a structural ceiling — an explicit Informational Note in the section. Running a duct just above the lay-in grid does not escape the rule.
110.26(E)(1)(b) Foreign Systems. The area above the dedicated space may contain foreign systems, provided protection is installed to avoid damage to the electrical equipment from condensation, leaks, or breaks in the foreign systems.
110.26(E)(1)(c) Sprinkler Protection. Sprinkler protection is permitted for the dedicated space where the piping complies with this section. In other words, a sprinkler system serving the room is not "foreign equipment" that must be relocated.
110.26(E)(1)(d) Suspended Ceilings. A dropped, suspended, or similar ceiling that does not add strength to the building structure shall not be considered a structural ceiling.
110.26(E)(2) Outdoor. Outdoor electrical equipment shall be installed in suitable enclosures and shall be protected from accidental contact by unauthorized personnel, or by vehicular traffic, or by accidental spillage or leakage from piping systems. The working-clearance rules of 110.26 still apply, and the space equal to the width and depth of the equipment, and extending from grade to a height of 6 feet above the equipment, shall be dedicated to the electrical installation.
Guarding of Live Parts — 110.27
110.27(A) Live Parts Guarded Against Accidental Contact. Except as elsewhere required or permitted, live parts of electrical equipment operating at 50 volts or more shall be guarded against accidental contact by approved enclosures or by any of the following:
- Location in a room, vault, or similar enclosure accessible only to qualified persons;
- A suitable permanent, substantial partition or screen so arranged that only qualified persons have access; openings must be sized so that persons are not likely to come into accidental contact or bring conducting objects into contact;
- Location on a suitable balcony, gallery, or platform elevated and arranged to exclude unqualified persons;
- Elevation of 8 feet (2.5 m) or more above the floor or other working surface.
110.27(B) Prevent Physical Damage. In locations where electrical equipment is likely to be exposed to physical damage, enclosures or guards shall be so arranged and of such strength as to prevent such damage.
110.27(C) Warning Signs. Entrances to rooms and other guarded locations containing exposed live parts shall be marked with conspicuous warning signs forbidding unqualified persons to enter. Signs must meet 110.21(B): they must not be handwritten, must be permanently affixed, and must be of sufficient durability for the environment.
Installations Over 1000 Volts Nominal — 110 Part III
Part III of Article 110 supplements the general rules for higher-voltage installations. The journeyman scope in 8 AAC 90.900(10) starts at the secondary side of the transformer, so medium-voltage work appears less often, but Alaska industrial, mine, and remote-generation sites do contain over-1000-V equipment and the rules are fair exam material.
110.31 Enclosure for Electrical Installations. Electrical installations in a vault, room, or closet, or in an area surrounded by a wall, screen, or fence, access to which is controlled by lock and key or other approved means, are considered accessible to qualified persons only. Fences must be at least 7 feet (2.1 m) high, or 6 feet high with a 1-foot barbed-wire extension, for an unattended outdoor installation.
110.32 Work Space About Equipment. Sufficient space shall be provided and maintained about electrical equipment to permit ready and safe operation and maintenance, with a minimum headroom of 6.5 feet (2.0 m).
110.33 Entrance and Access to Work Space. At least one entrance not less than 24 inches wide and 6.5 feet high shall be provided. Where the voltage exceeds 1000 V, unguarded live parts above the working space must be maintained at the elevations specified in Table 110.34(E).
110.34(A) Working Space. Depth is taken from a table indexed by voltage and by the same Condition 1, 2, and 3 scheme used in 110.26 — for example, 1001 to 2500 volts requires 3 feet, 4 feet, and 5 feet for Conditions 1, 2, and 3 respectively.
110.34(C) Warning Signs. "Permanent and conspicuous warning signs shall be provided, reading as follows: DANGER — HIGH VOLTAGE — KEEP OUT."
110.34(E) Illumination and 110.34(F) Ventilation round out the section, requiring adequate lighting and ventilation for over-1000-V rooms and vaults.
Alaska Field Note
Dedicated-space violations are among the most common findings on Alaska commercial inspections, and the reason is climate. Buildings in the Interior and on the North Slope carry heavy mechanical loads — glycol loops, heat-trace headers, ventilation ducting, and snowmelt piping — all of which want the same ceiling cavity as the panel feeders. The rule does not bend for cold weather: piping and ducts foreign to the electrical installation are prohibited in the column above the gear up to 6 feet or the structural ceiling. The compliant approach is to coordinate the routing during layout, or to install the leak protection required by 110.26(E)(1)(b) for systems located above the dedicated space.
A panelboard is mounted in a mechanical room where the structural ceiling is 9 feet above the floor. The top of the panelboard is at 6 feet 6 inches. To what height does the dedicated equipment space extend under NEC 110.26(E)(1)(a)?
A contractor routes a glycol heating line through a suspended ceiling directly above a motor control center, 3 feet above the top of the equipment. Is this permitted?
Under NEC 110.27(A), at what minimum elevation above the floor or working surface may live parts be located as the sole means of guarding against accidental contact?
What exact wording does NEC 110.34(C) require on permanent warning signs at entrances to rooms containing exposed live parts over 1000 volts?