E2 Working Space and Clearances 3 — Questions and Answers
Question 1: What is the maximum voltage allowed to still qualify for the 3-foot minimum working space depth under Condition 1 per NEC 110.26(A)(1)?
- 150V to ground
- 151V to 600V
- 600V nominal or less (Correct answer)
- Up to 300V nominal
Correct answer: 600V nominal or less
NEC 110.26(A)(1) Table applies to equipment operating at 600V nominal or less, with Condition 1 requiring a minimum 3-foot working space depth for this voltage range.
Question 2: A technician needs to work on a 480V panelboard where one side has an exposed energized bus and the opposite side has a concrete block (grounded) wall. Which working space Condition applies?
- Condition 1
- Condition 2 (Correct answer)
- Condition 3
- Condition 4
Correct answer: Condition 2
Condition 2 applies when there are exposed live parts on one side and grounded parts (such as a concrete/masonry wall) on the other side.
Question 3: According to NEC 110.26(C)(1), how many means of egress are required for a room with electrical equipment rated 1200A or more and over 6 feet wide when the room exceeds 50 feet in length?
- One entrance at either end
- Two entrances located at each end of the working space (Correct answer)
- Three entrances distributed along the length
- One entrance with a panic bar
Correct answer: Two entrances located at each end of the working space
NEC 110.26(C)(1) Exception requires two entrances located at each end of the working space for rooms exceeding 50 feet in length with large equipment.
Question 4: Pipes, ducts, or equipment foreign to electrical installations are permitted in dedicated electrical space under which condition?
- Never — NEC strictly prohibits all foreign systems (Correct answer)
- Only when approved by the authority having jurisdiction
- When they are located above the electrical equipment zone
- Only if they are installed before the electrical equipment
Correct answer: Never — NEC strictly prohibits all foreign systems
NEC 110.26(F)(1)(b) states that the dedicated space shall not be used for piping, ducts, leak protection apparatus, or any equipment foreign to the electrical installation.
Question 5: What is the required working space depth for 480V equipment (Condition 2) per NEC 110.26(A)(1)?
- 3 feet
- 3.5 feet
- 4 feet (Correct answer)
- 5 feet
Correct answer: 4 feet
Per NEC 110.26(A)(1) Table, for voltages from 151V to 600V under Condition 2, the minimum working space depth is 3.5 feet.
Question 6: Which NEC provision allows the working space in front of electrical equipment to serve as egress, and what is the key requirement?
- NEC 110.26(C)(3) — the workspace must be at least 30 inches wide
- NEC 110.26(C)(2) — the path must not pass through the working space of other equipment (Correct answer)
- NEC 110.26(C)(1) — the door must swing in the direction of egress
- NEC 110.26(A)(3) — the aisle must exceed 48 inches
Correct answer: NEC 110.26(C)(2) — the path must not pass through the working space of other equipment
NEC 110.26(C)(2) permits the working space to serve as an egress path, but the path must not require passing through the working space of other electrical equipment.
Question 7: For outdoor electrical equipment, what does NEC 110.26(F)(2) require regarding dedicated space?
- A concrete pad must extend 3 feet beyond all sides of the equipment
- The space above and below the equipment must be kept clear of piping and other systems
- No foreign equipment within 10 feet horizontally of the electrical equipment
- Outdoor equipment is exempt from dedicated space requirements (Correct answer)
Correct answer: Outdoor equipment is exempt from dedicated space requirements
NEC 110.26(F)(2) states that outdoor electrical equipment is not required to have a dedicated electrical space, as this provision applies only to indoor installations.
E2 Working Space and Clearances 3
What is the maximum voltage allowed to still qualify for the 3-foot minimum working space depth under Condition 1 per NEC 110.26(A)(1)?