How it works & the NEC rules behind it
Under NEC §110.26, sufficient access and working space must be provided and maintained around all electrical equipment to permit ready and safe operation and maintenance.
Three Dimensions of Working Space (NEC §110.26(A)):
- 1. Working Depth (Table 110.26(A)(1)): Measured from the enclosure front. Depends on voltage to ground and opposite surface condition:
- Condition 1: Exposed live parts on one side, insulated or non-grounded wall opposite (e.g. wood frame).
- Condition 2: Exposed live parts on one side, grounded surface opposite (concrete, brick, tile, sheetrock on metal studs). Most common commercial condition.
- Condition 3: Exposed live parts on both sides of the working space (e.g. facing switchboards).
- 2. Working Width (§110.26(A)(2)): Must be at least 30 inches (762 mm) or the full width of the equipment, whichever is greater. Equipment doors must open to at least 90 degrees.
- 3. Working Height / Headroom (§110.26(A)(3)): Must extend from the floor to at least 6.5 feet (2.0 m) or the equipment height.
- 4. Dedicated Electrical Space (§110.26(E)): The footprint of the panel extending to 6 feet above the equipment (or structural ceiling) is strictly reserved for electrical equipment — no plumbing, gas pipes, or HVAC ducts allowed!
- 5. Large Equipment (§110.26(C)(2)): Equipment rated 1,200 Amps or more and over 6 ft wide requires two egress exits with panic hardware opening in the direction of egress.