How Much Working Space Is Enough?

Jan 1, 2009 12:00 PM, By Mike Holt, NEC Consultant

Don’t assume 3 ft of working space applies in all situations

In order to create safe working conditions, OSHA and the NEC [110.26] provide working space requirements that vary according to the hazards involved with the installation and equipment. The NEC starts 110.26 by stating the space must be sufficient for “ready and safe operation and maintenance” of electrical equipment. This general statement applies to all electrical equipment. This single condition sets the stage for the more specific requirements found in 110.26.

Fig. 1. Working space can be measured from left to right, right to left, or simply from the centerline of the equipment.

When applying the requirements, the goal isn't to see what you can get by with. It's to protect people from injuries due to electric shock and arc blast/arc flash. Consequently, you may want to exceed the numbers given in 110.26 to satisfy the intent of this section. Think through the work processes that are likely to occur in the area. For example, is there enough room to safely use a lifting boom on that heavy breaker?

Requirement exceptions

Per 90.3, the working space requirements of 110.26 don't apply to equipment included in Chapter 8. Although signaling and communications equipment don't require a clear working space, they can't encroach on the working space of the electrical equipment.

The NEC doesn't require working space for the back or sides of an assembly where all connections and renewable or adjustable parts are accessible from the front [110.26(A)(1)(a)].

Fig. 2. Equipment must not extend more than 6 in. into the equipment’s working space.

Where special permission is granted in accordance with 90.4, working space for equipment that operates at not more than 30VAC or 60VDC can be less than the distance in Table 110.26(A)(1) [110.26(A)(1)(b)]. Read the definition of “Special Permission” in Art. 100.

If you're replacing electrical equipment, you can apply Table 110.26(A)(1) Condition 2 working space requirements between dead-front switchboards, panelboards, or motor control centers located across the aisle from each other [110.26(A)(1)(c)] — but only if:

Width, depth, and height

Conditions of maintenance and supervision ensure that written procedures have been adopted to prohibit equipment on both sides of the aisle from being open at the same time, and
Only authorized, qualified persons will service the installation.

Fig. 3. When it comes to the dedicated footprint space of electrical equipment, there are strict rules pertaining to the installation of piping, ducts, or other equipment foreign to the electrical installation.

A common area of disagreement is the phrase “likely to require” in 110.26(A), which says, “Equipment that is likely to require examination, adjustment, servicing, or maintenance while energized must have sufficient working space in accordance with (1), (2), and (3)….” Get clarification on what “likely to require” means from the Authority Having Jurisdiction (AHJ).

In all cases, the working space must be of sufficient width, depth, and height to permit all equipment doors to open 90° [110.26(A)(2)].

The width of the working space must be a minimum of 30 in., but in no case less than the width of the equipment.

You can measure the width of the working space from left to right, from right to left, or simply centered on the equipment. The working space for one piece of equipment can overlap the working space for other electrical equipment (Fig. 1 on page 32).

See Table 110.26(A)(1) for the minimum depth required of a specific application — it's not always 3 ft. For example, it's 4 ft at a 480V motor control center (MCC) with exposed live parts on both sides of the working space.

“Headroom” is another way we refer to the height of a working space. For service equipment, switchboards, panelboards, and motor control equipment, the headroom in front of equipment must be at least 6½ ft, measured from the grade, floor, or platform [110.26(E)]. For equipment more than 6½ ft in height, the headroom can't be less than the height of the equipment.