SFB-2 — Service Conductors, Drops, Laterals, and Clearances

Begin at the service point

Article 100 definitions prevent jurisdiction and conductor-name errors. A service is the conductors and equipment that deliver electric energy from the serving utility to the premises wiring system. The service point is the connection between the serving utility's facilities and the premises wiring. The utility and owner establish that point; do not assume it is always the meter.

A service drop consists of overhead conductors between the utility supply system and the service point. A service lateral consists of underground conductors between the utility supply system and the service point. Service conductors extend from the service point to the service disconnecting means. Conductors on opposite sides of the service point can be physically similar but have different Code names and responsibilities.

NEC 90.2(B)(5) excludes qualifying utility installations under exclusive utility control. Once premises wiring begins, applicable NEC service rules govern. The serving utility can impose construction standards beyond NEC minimums, including attachment height, mast strength, conductor routing, and meter location. Both requirements must be satisfied.

Apply overhead vertical clearances conditionally

Section 230.24 requires service-drop conductors to be located so they are not readily accessible and establishes clearances for systems not over 600 V nominal. Under 2017 NEC 230.24(B), select the exact condition:

• 10 ft at the building service entrance, at the lowest point of the drip loop, and above areas or sidewalks accessible only to pedestrians, measured from final grade or another accessible surface, only for service-drop cable supported on and cabled with a grounded bare messenger where voltage does not exceed 150 V to ground.
• 12 ft over residential property and residential driveways, and over commercial areas not subject to truck traffic, where voltage is limited to 300 V to ground.
• 15 ft over the areas described in the 12 ft rule where voltage exceeds 300 V to ground.
• 18 ft over public streets, alleys, roads, parking areas subject to truck traffic, driveways on property other than residential, and other land traversed by vehicles, including cultivated, grazing, forest, and orchard land.

These are minimum vertical clearances under stated assumptions. Example: assume a 120/240 V, single-phase service drop crosses a one-family dwelling driveway, with 120 V to ground and no special condition. Section 230.24(B)(2) requires 12 ft. The same conductors crossing a public street require 18 ft under 230.24(B)(4). Do not choose 10 ft merely because voltage is 120 V to ground; the surface below still controls.

Clearance is measured from final grade or the applicable accessible surface. Construction grading, paving, decks, or raised platforms can change the final relationship. Preserve clearance over the complete span, including conductor sag under applicable conditions.

Check roofs, openings, and attachment

Under 230.24(A), service-drop conductors generally maintain 8 ft of vertical clearance above roof surfaces. The section contains specific exceptions for voltage, roof slope, area overhang, accessibility, and conductor arrangement. Apply an exception only after verifying every condition; “residential roof” alone is not an exception.

Section 230.9 addresses clearances from building openings for service conductors installed as open conductors or multiconductor cable without an overall outer jacket. A 3 ft clearance generally applies from windows designed to open, doors, porches, balconies, ladders, stairs, and fire escapes, with stated exceptions. Conductors cannot be installed beneath openings through which materials may be moved, such as farm or commercial building openings, unless protected as permitted.

The point of attachment must provide the clearances required by 230.24. A service mast used for support must have adequate mechanical strength under 230.28, and only service-drop or overhead service conductors may be attached to it.

Service heads and goosenecks are arranged to reduce water entry, and raceways exposed to weather must remain raintight as required. Drip loops help prevent water from following conductors into equipment. These details do not reduce the required conductor clearance.

Trace underground service routes

A service lateral ends at the service point; underground service conductors continue from that point toward the service equipment. Determine ownership and point location before applying premises-wiring burial rules. Where Table 300.5 applies, minimum cover depends on wiring method, location, voltage, residential use, vehicular exposure, and special conditions. There is no universal “service lateral depth.”

Underground raceway interiors are wet locations under 300.5(B), so conductors and cables within must be listed for wet locations. Section 230.8 requires sealing raceways where they enter a building from underground in accordance with 300.5(G), and spare or unused raceways must also be sealed. The seal addresses moisture or gas migration; it is not automatically the same as a hazardous-location seal.

Underground service conductors subject to physical damage require protection under 230.50 and the permitted methods. Section 230.6 identifies conditions under which service conductors are considered outside a building, such as specified encasement or routing. Section 230.7 generally prevents service conductors from sharing a raceway or cable with feeder or branch-circuit conductors, subject to the conductors the section permits.

Use a complete service checklist

For every service-route question, identify: overhead or underground; service point; voltage to ground; conductor or cable construction; surface below; pedestrian, residential-vehicle, truck, or public-road exposure; final grade and sag; roof and opening relationships; support and attachment; wet-location and physical protection; and special rules. Pools and other special installations can add requirements beyond Article 230.

Article 230 supplies enforceable installation minimums. An Informational Note or utility drawing may explain good design, but it does not silently replace Code text. Conversely, meeting a minimum NEC clearance does not override a utility's greater service standard or authorize attachment to utility facilities without coordination.