For voltages 1000 V or less, the spacing of open service conductors in dry locations is 2 1/2 inches. Which option represents this spacing?

• A. 2 1/2 inches
• B. 3 inches
• C. 2 inches
• D. 4 inches

Answer: (A)

Minimum clearance between open service conductors in dry locations for voltages not exceeding 1000 V is two and a half inches. This spacing is set to ensure there’s enough air insulation to prevent arcing under normal conditions, protecting people and equipment from unintended conductance between conductors.

Two and a half inches is the exact value specified for this voltage range and environment, so it’s the correct match. Spacing smaller than that would not meet the requirement and could risk arcing, while larger spacings are not the defined value for this particular category. In higher voltages or different locations, the required spacing would change, but for this case the two and a half inch gap is what the standard calls for.