E2 Working Space and Clearances 2 — Questions and Answers
Question 1: According to NEC 110.26, what is the minimum width of working space in front of electrical equipment rated 600V or less?
- The width of the equipment or 24 inches, whichever is greater
- The width of the equipment or 30 inches, whichever is greater (Correct answer)
- 36 inches regardless of equipment width
- 30 inches regardless of equipment width
Correct answer: The width of the equipment or 30 inches, whichever is greater
NEC 110.26(A)(2) requires the width of working space to be at least 30 inches or the width of the equipment, whichever is greater.
Question 2: When electrical equipment rated over 1000V is installed, NEC 110.34 specifies working space conditions. For Condition 1, what is the minimum depth of working space for equipment up to 2.5kV?
- 3 feet
- 4 feet (Correct answer)
- 5 feet
- 6 feet
Correct answer: 4 feet
NEC 110.34(A) Table specifies a minimum working space depth of 4 feet for Condition 1 at voltages up to 2.5kV.
Question 3: What does NEC 110.26(A)(1) Condition 3 describe regarding working space?
- Exposed live parts on one side and grounded parts on the other
- Exposed live parts on both sides with no insulated barrier (Correct answer)
- Grounded parts on both sides of the working space
- Insulated parts on one side and a wall on the other
Correct answer: Exposed live parts on both sides with no insulated barrier
Condition 3 involves exposed energized parts on both sides of the working space with no insulated or guarded barrier separating them.
Question 4: Which NEC section governs the illumination requirements for working spaces about electrical equipment?
- NEC 110.26(D) (Correct answer)
- NEC 110.26(E)
- NEC 110.26(C)
- NEC 110.26(F)
Correct answer: NEC 110.26(D)
NEC 110.26(D) requires adequate illumination for all working spaces about electrical equipment.
Question 5: A commercial switchboard is 52 inches wide. What is the minimum required working space width in front of it?
- 30 inches
- 36 inches
- 52 inches (Correct answer)
- 60 inches
Correct answer: 52 inches
NEC 110.26(A)(2) requires the working space width to be the width of the equipment (52 inches) or 30 inches, whichever is greater, so 52 inches applies.
Question 6: Under NEC 110.26(B), what is the minimum headroom for working spaces about service equipment, switchboards, and panelboards?
- 6 feet
- 6 feet 3 inches (Correct answer)
- 6 feet 6 inches
- 7 feet
Correct answer: 6 feet 3 inches
NEC 110.26(B) requires a minimum headroom of 6 feet 3 inches for working spaces about service equipment, switchboards, panelboards, and motor control centers.
Question 7: When must a dedicated electrical space extend from the floor to a structural ceiling per NEC 110.26(F)(1)(a)?
- Only for equipment rated over 1200A
- For all indoor electrical equipment rated 1000V or less (Correct answer)
- When the equipment exceeds 6 feet in height
- Only for switchboards and panelboards, not for branch circuit panels
Correct answer: For all indoor electrical equipment rated 1000V or less
NEC 110.26(F)(1)(a) requires the dedicated electrical space to extend from the floor to the structural ceiling for indoor electrical equipment rated 1000V or less.
E2 Working Space and Clearances 2
According to NEC 110.26, what is the minimum width of working space in front of electrical equipment rated 600V or less?