Overhead Conductor Clearance From Buildings Calculator

Clearance from buildings, 1000 V or less

The clearance depends on the surface the conductors pass, and for two surfaces the answer is a rule rather than a distance. The 3 ft values are the same for service conductors (230.9) and outside feeders (225.19); the nonbuilding-structure and general horizontal-clearance rows are unique to outside feeders.

The 3 ft clearance is required at the sides and below an openable window, but not directly above it, and not from a window that cannot be opened. Those two carve-outs are where the rule is most often read too strictly or too loosely.

Openable windows only, and never above them

NEC 230.9(A) and 225.19(D)(1) tie the 3 ft standoff to windows that are designed to be opened, because the hazard is a person reaching an energized conductor from the opening. A fixed picture window is not such an opening, so it does not force the 3 ft clearance. The code also states an exception for conductors run above the top level of a window: a service drop that passes over the head of a window can be closer than 3 ft, since the window cannot be used to reach up and over the conductors. The 3 ft still governs at the sides and below.

Worked example: a service drop along a house wall

A 120/240 V overhead service drop runs to a masthead on the side of a house. Along the wall it passes an openable bedroom window and a second-floor balcony. Under 230.9(A) the open conductors must clear 3 ft from the openable window and 3 ft from the balcony, measured to the sides and below. Where the drop passes above the top of a fixed stairwell window, the above-window exception applies and it may be closer than 3 ft. If a reachable porch roof or platform sits under the run, 230.9(B) adds that within 3 ft horizontally of that surface the span still has to meet the vertical clearance of 230.24(B), so the two rules stack.

Now take an outside feeder run to a detached shop that passes a wall-mounted sign and a rooftop antenna. Under 225.19(B) the feeder must clear 3 ft in any direction from the sign and the antenna, and 225.19(C) holds the same 3 ft general horizontal clearance from the wall. Service section 230.9 has no nonbuilding-structure rule, so those surfaces are only available under the outside-feeder scope in this tool.

Common mistakes

• Applying 3 ft to a fixed window. The rule reaches windows designed to be opened. A window that cannot open is not an opening it applies to.
• Enforcing 3 ft directly above a window. The code states an exception for conductors above the top level of a window; the 3 ft holds at the sides and below.
• Looking for the sign or antenna clearance under 230.9. The 3 ft clearance from signs, chimneys, antennas, and tanks is the outside-feeder rule 225.19(B); 230.9 for service conductors does not list it.
• Treating the material-moving opening as a distance. 230.9(C) and 225.19(D)(3) prohibit running the conductors beneath a loading opening or where they block entrance; there is no 3 ft number that makes it acceptable.
• Confusing clearance from the building with clearance over the ground. The horizontal 3 ft standoff here is separate from the 10, 12, 15, and 18 ft vertical clearances of 230.24 and 225.18.

Frequently asked questions

How far do service conductors have to be from a window?

Under 230.9(A) open overhead service conductors clear 3 ft from windows designed to be opened, doors, porches, balconies, ladders, stairs, and fire escapes. The space directly above the top of a window is a stated exception, and a fixed window is not an opening the rule reaches.

Does 3 ft apply to a fixed window?

No. The 3 ft clearance in 230.9(A) and 225.19(D)(1) applies to windows designed to be opened. A fixed or inoperable window is not covered, and neither is the space directly above the top of any window.

What is the feeder clearance from a sign or antenna?

225.19(B) requires outside branch circuits and feeders to clear signs, chimneys, antennas, tanks, and other nonbuilding structures by 3 ft in any direction, and 225.19(C) sets the same 3 ft general horizontal clearance. Service section 230.9 does not address nonbuilding structures.

Can conductors run over a loading opening?

No. 230.9(C) and 225.19(D)(3) prohibit running the conductors beneath openings through which materials may be moved, and where they would obstruct entrance to the opening. It is a prohibition, not a clearance you can satisfy with distance.

How is this different from overhead clearance?

This tool is the horizontal clearance of conductors from buildings and structures under 230.9 and 225.19(B) through (D). The vertical clearance of the span over the ground or a roof is 230.24 and 225.18, handled by the Overhead Conductor Clearance Calculator.

Related calculators

• Overhead Conductor Clearance Calculator: the vertical clearance of an overhead span over the ground or a roof per NEC 230.24 and 225.18.
• Working Space Clearance Calculator: the horizontal working space in front of equipment per NEC 110.26(A).
• Service Size Calculator: size the service disconnect, conductors, and grounding electrode conductor.
• Dwelling Service Conductor Calculator: size the service-entrance conductors under the Table 310.12 dwelling allowance.