A plumber proposes running a drain line through the space directly above a surface-mounted panelboard in an indoor electrical room. What does the Code require for that zone?
- The zone equal to the width and depth of the panelboard, up to 6 ft above it or to the structural ceiling if that is lower, must stay clear of foreign systems
- BPiping may pass directly above the panelboard as long as it clears the top of the enclosure by at least 3 ft and is fitted with a drip pan
No standoff allowance exists for foreign piping above electrical equipment. The dedicated zone is defined by the equipment footprint and a fixed height, so a drain line inside that column violates the rule at any clearance.
- CThe dedicated space extends from the floor all the way to the structural ceiling in every installation, regardless of how high the ceiling in that room happens to be
The dedicated space stops 6 ft above the equipment whenever the structural ceiling is higher than that. Extending it further than the rule requires gives away usable space in tall rooms and misstates what an inspector can enforce.
- DForeign systems are permitted above the equipment whenever the panelboard is rated 200 amperes or less and is mounted on the surface of the wall
Ampere rating and mounting style play no part in the dedicated space rule. A small lighting panel gets the same protected column above it as a large distribution panel, which is what makes the rule straightforward in the field.
Why A is correct
The dedicated space is a column, not a clearance. It has the same width and depth as the equipment and rises 6 ft above it, or stops at the structural ceiling if the ceiling is lower than that. Inside that column, nothing foreign to the electrical installation may be installed, which is what keeps a drain line from ever crossing the top of a panel.
What this question is testing
This checks whether you can keep dedicated equipment space and working space apart in your head, since they live in the same Code section and are constantly conflated. It also checks the whichever is lower qualifier, which candidates routinely drop.
On the job
Coordination fights in mechanical rooms almost always come down to this column. Plumbing wants the shortest route, sheet metal wants the straightest duct, and the panel is already on the wall. The rule protects the gear from a leak or a condensate drip that would otherwise land on energized bus. It is separate from the working space in front of the equipment, so a compliant job has to satisfy both: clear depth and width in front for a person to work, and a clear column above for the equipment itself.
Memory technique
Nothing foreign in the six-foot column over the panel.
Exam tip
Dedicated space protects the equipment and runs upward; working space protects the worker and runs outward. Keep the two questions separate.
Where to look it up
Article 110, spaces about electrical equipment, in the subsection on dedicated equipment space. Indoor and outdoor cases are handled separately.