Free E2 Working Space and Clearances Questions and Answers 1 — Questions and Answers
Question 1: What is the minimum depth of working space required in front of a 480V switchboard with exposed live parts on one side and grounded parts on the other side?
- 3 feet
- 3 feet 6 inches (Correct answer)
- 4 feet
- 5 feet
Correct answer: 3 feet 6 inches
According to NEC Table 110.26(A)(1), for systems with a nominal voltage to ground of 151-1000V, Condition 2 (Exposed live parts on one side and grounded parts on the other side) requires a minimum clear distance of 3 feet 6 inches.
Question 2: The minimum required width of the working space in front of a 24-inch wide panelboard must be:
- 24 inches
- 36 inches
- The width of the panelboard plus 6 inches
- 30 inches (Correct answer)
Correct answer: 30 inches
NEC 110.26(A)(2) states the width of the working space shall be the width of the equipment or 30 inches, whichever is greater. Since the panelboard is 24 inches wide, the minimum required working space width is 30 inches.
Question 3: What is the minimum headroom of working space required for service equipment located in a commercial building?
- 6 feet
- 6 feet 6 inches or the height of the equipment, whichever is greater (Correct answer)
- 7 feet
- The height of the equipment only
Correct answer: 6 feet 6 inches or the height of the equipment, whichever is greater
As per NEC 110.26(E), the minimum headroom of working spaces about service equipment, switchboards, and panelboards shall be 6 feet 6 inches or the height of the equipment, whichever is greater. This ensures adequate vertical space for personnel.
Question 4: A large switchboard is rated 1200 amperes and is over 6 feet wide. What is required for personnel entrance and egress?
- One entrance of at least 36 inches wide
- Panic hardware on all doors within 25 feet
- One entrance at each end of the working space (Correct answer)
- A single entrance located in the center of the equipment
Correct answer: One entrance at each end of the working space
NEC 110.26(C)(2) requires one entrance to and egress from the required working space not less than 24 inches wide and 6 feet 6 inches high at each end of the working space for equipment rated 1200 A or more and over 6 ft wide. This provides two paths of exit in case of an emergency.
Question 5: Equipment doors that open into the required working space must be able to open to an angle of at least:
- 45 degrees
- 75 degrees
- 90 degrees (Correct answer)
- 180 degrees
Correct answer: 90 degrees
NEC 110.26(A)(3) requires that where equipment doors are installed, they must be able to open to at least a 90-degree position. This ensures that the doors do not obstruct the required working space when service is being performed.
Question 6: Illumination shall be provided for all working spaces about service equipment, switchboards, panelboards, or motor control centers installed:
- Outdoors only
- Indoors (Correct answer)
- In wet locations only
- Only if the voltage exceeds 240V
Correct answer: Indoors
NEC 110.26(D) mandates that illumination be provided for these working spaces when they are installed indoors. This requirement ensures that personnel can perform tasks safely and effectively, regardless of the ambient light in the larger space.
Free E2 Working Space and Clearances Questions and Answers 1
What is the minimum depth of working space required in front of a 480V switchboard with exposed live parts on one side and grounded parts on the other side?