4.1 Service Entrance Conductors and Service Point
Key Takeaways
- The service point is the exact boundary where utility-owned conductors end and customer-owned conductors begin — it is the dividing line for NEC jurisdiction under Article 230.
- Service-entrance conductors on the line side of the service disconnect are governed by Article 230, not by general wiring rules in Articles 310 and 320/330.
- Overhead service-drop conductors must maintain the clearances in NEC 230.24: 10 ft over residential property, 12 ft over commercial driveways, and 18 ft over public streets.
- Minimum service-entrance conductor size for a dwelling is set by 230.42 and must carry the calculated load, but never smaller than the conductors required by 230.79 for the service disconnect rating.
- The service head (gooseneck) must be installed so rain cannot enter the raceway or cable, and drip loops must form the lowest point of the conductor run per 230.52 and 230.54.
Why Service Entrance Matters on the TX Journeyman Exam
The Texas Journeyman exam's Knowledge part (59 questions, 130 minutes) tests your ability to identify the correct NEC article, term, or rule. Area 2 of the TDLR content outline — Services, Service Equipment, and Separately Derived Systems — begins at the service point, the boundary that determines who owns which conductor and which code article applies. Misidentifying the service point is one of the most common exam errors because it shifts the applicable article from 230 (Services) to 320/330 (Feeder/Service-Entrance cables) or to utility NESC rules that the NEC does not cover. On the Calculations part (26 questions, 110 minutes), service conductor sizing appears when you must select a conductor from Table 310.16 after computing the service load.
Core Definitions (NEC Article 100 + Article 230 Part I)
The NEC defines several closely related terms that the exam will distinguish:
- Service point: The point of connection between the serving utility's facilities and the premises wiring. Everything on the utility side is not covered by the NEC; everything on the customer side is.
- Service conductors: Conductors from the service point to the service disconnecting means. This broad term includes service drops, service laterals, and service-entrance conductors.
- Service-entrance conductors: The customer-owned portion of the service conductors — from the service point (or service head/meter) to the service disconnect.
- Service drop: Overhead service conductors between the utility pole and the service point.
- Service lateral: Underground service conductors between the utility transformer and the service point.
- Service equipment: The conductors and equipment that deliver electric power from the serving utility to the wiring system of the premises, located at or near the service point.
A high-yield exam distinction: service drop vs. service lateral is purely overhead vs. underground. Both are service conductors, but the clearance, raceway, and protection rules differ.
Article 230 Part II — Service-Entrance Conductors (Overhead)
NEC 230.40 requires each service drop or lateral to supply only one set of service-entrance conductors, with limited exceptions (multiple buildings, different voltage systems, or a second service for fire pumps). 230.42 sets the minimum size: service-entrance conductors must have sufficient ampacity to carry the service load calculated under Article 220, and they must never be smaller than required by 230.79 for the service disconnect rating. For a typical dwelling, the practical floor is the 100-amp minimum disconnect rating in 230.79(C), which pushes the conductor to at least 4 AWG copper (Table 310.16, 75 °C column = 85 A; 3 AWG = 100 A).
Common Service-Entrance Conductor Types
| Conductor Type | Insulation | Application | NEC Reference |
|---|---|---|---|
| SE (Service-Entrance cable) | Flame-retardant, moisture-resistant | Above-ground service runs, conduit optional where permitted | Article 338 |
| USE-2 (Underground Service-Entrance) | RHW-2/USE-2, 90 °C wet | Underground lateral runs, direct burial | 338.10(B)(2) |
| RHH/RHW-2 | 90 °C dry, 90 °C wet | Raceway or direct burial | Table 310.4(1) |
| THWN-2 | 90 °C dry, 90 °C wet | Wet raceways, conduits | Table 310.16 |
| XHHW-2 | 90 °C dry, 90 °C wet | Raceway, sunlight-resistant for outdoors | Table 310.16 |
A frequent exam trap: SE cable used as interior wiring must have its outer nonmetallic sheath removed inside the building (338.10(B)) because the sheath is not rated for flame spread inside a structure.
Article 230 Part III — Underground Service-Lateral Conductors
230.49 covers protection against physical damage for underground service conductors: they must be in raceway (RMC, IMC, or Schedule 80 PVC) when they enter a building, and the raceway must extend from the service head or meter enclosure to a point not less than 450 mm (18 in.) below grade. Direct-buried USE-2 must be buried at least 760 mm (30 in.) for residential (300.5 Table, column 1) unless one of the reduced-depth exceptions (e.g., 150 mm with concrete cover) applies.
Clearances — 230.24 and 230.9
230.24(A) fixes the minimum vertical clearance of overhead service-drop conductors above finished grade, rooftop, or platform:
| Location | Minimum Clearance |
|---|---|
| Over residential property, sidewalks, decks | 10 ft (3.0 m) |
| Over commercial property subject to truck traffic | 12 ft (3.7 m) |
| Over driveways and parking lots | 12 ft (3.7 m) |
| Over public streets, alleys, roads | 18 ft (5.5 m) |
| Over swimming pools (Art. 680) | 22.5 ft (conductors over 750 V to ground) |
230.9 requires horizontal clearance from building openings: service conductors must maintain at least 3 ft (900 mm) from windows, doors, porches, fire escapes, and similar openings, and must not pass beneath openings through which materials may pass.
230.26 requires the point of attachment for overhead service conductors to be located so that the service drop meets the 230.24 clearances, with a minimum height of 10 ft at the attachment point for residential and 18 ft where subject to truck traffic.
Service Head, Drip Loops, and Raceway Rules
- 230.52: Individual conductors of a service drop must be attached to a service head or gooseneck that prevents water from entering the raceway or cable.
- 230.54(A): Service heads must be located above the point of attachment of the service drop, and the conductors must form a drip loop below the service head so rain runs off the loop, not into the head.
- 230.54(F): Where the service-entrance conductors enter a raceway, the raceway must extend from the service head or meter to the service equipment and be sealed against weather.
- 230.43: Wiring methods for service-entrance conductors include RMC, IMC, EMT (intermediate), ENT (limited), Type SE cable, and wireways. NM (Romex) is not permitted as a service-entrance conductor.
Conductor Sizing Worked Example
A 150-amp residential service requires service-entrance conductors in a raceway. Using Table 310.16, copper, 75 °C column (equipment terminations for service equipment rated 100 A or larger are rated 75 °C per 110.14(C)(1)(b)):
- 1 AWG Cu = 130 A → too small for 150 A
- 1/0 AWG Cu = 150 A → meets the 150 A rating exactly
If the load calculation yielded only 135 A, the next standard service size is 150 A, and 1/0 AWG Cu still applies. The conductor ampacity must equal or exceed the service disconnect rating, not just the calculated load.
Exam Takeaways
- Service point = jurisdiction boundary. Conductors on the load side of it are NEC-governed.
- Service drop = overhead; service lateral = underground. Both feed service-entrance conductors.
- 230.42 sizing: ampacity ≥ calculated load AND ≥ 230.79 disconnect rating.
- Clearances: 10 / 12 / 18 ft from lowest to highest-risk locations.
- NM cable is never a service-entrance conductor.
What is the minimum vertical clearance for overhead service-drop conductors over a residential yard and sidewalk?
Which wiring method is NOT permitted for service-entrance conductors under NEC 230.43?