NEC panel clearance requirements: 110.26 working space rules

What working-space depth does NEC 110.26 require?

Per NEC 110.26(A)(1), the minimum depth of working space in front of an electrical panel is based on voltage and the condition of what's behind the working space (grounded parts, exposed live parts, etc.). The minimum width is the greater of 30" or the width of the equipment. The minimum headroom is 6'-6" (or the height of equipment if taller).

How does NEC set working-space depth?

Depth depends on nominal voltage to ground and three conditions around the equipment.

• Condition 1 (exposed live parts on one side, no live or grounded parts on the other): 3'-0" for 0–150 V, 3'-6" for 151–600 V, 4'-0" for 601–2500 V
• Condition 2 (exposed live parts on one side, grounded parts on the other): 3'-0" / 3'-6" / 4'-6" / 5'-0" at increasing voltages
• Condition 3 (exposed live parts on both sides): 3'-0" / 4'-0" / 5'-0" / 6'-0" at increasing voltages

For typical 277/480V panels (Condition 2): 3'-6" minimum depth. For 208V panels (Condition 1): 3'-0" minimum depth.

What width, height, and dedicated space does NEC require?

Beyond depth, NEC also sets width, height, and dedicated equipment space.

• Width (NEC 110.26(A)(2)): 30" minimum, or equipment width if greater. The width must extend from the floor to the height of the equipment or 6'-6", whichever is greater
• Height (NEC 110.26(A)(3)): 6'-6" minimum clearance above the working space, or the height of the equipment
• Dedicated space (NEC 110.26(E)): Space above the panel up to 6' or to structural ceiling, whichever is less, must be dedicated to electrical installation, no piping, ducts, or other non-electrical systems allowed
• Suspended ceilings: The dedicated space above drops out at the structural ceiling, but nothing foreign may pass through from above

What entry and egress rules apply to electrical rooms?

Rooms containing large equipment (over 1,200 amps, or over 6' wide) must have two entrances for egress, each not less than 24" wide and 6'-6" high. Doors must open in the direction of egress and be equipped with panic hardware or listed fire exit hardware.

This is a frequent drawing-review miss on tenant improvements where an existing electrical room gets new larger gear, suddenly the room needs two doors instead of one.

What illumination does NEC require in electrical rooms?

Electrical rooms containing service equipment, switchboards, panelboards, or MCCs must have illumination. Control must be accessible from the room entrance. Reading the light fixture schedule against the electrical room layout is a common review check.

What NEC 110.26 errors show up on drawings?

The usual 110.26 errors are missing working space, blocked dedicated space, and one-door rooms.

• Panels drawn with clearance extending into walls, doors, or columns
• Sprinkler piping routed through the dedicated space above a panel
• Storage room used as electrical room without the 110.26 clearance preserved
• Single door on a room over 1,200A/6'-wide
• Ladders and catwalks crossing into working space
• Door swing into the clearance depth (depth must be clear when door is open)

For broader electrical room design, see mechanical room clearances for the comparable mechanical-code requirements.