5.1 Service Entrance Requirements (Article 230)

Why Article 230 Matters on the Exam

The Virginia journeyman exam treats services as a distinct system from feeders and branch circuits. A service is the single point where utility power enters a building, and the NEC regulates it tightly because it is the only place where conductors are generally not protected by an overcurrent device on the line side. Expect 5-10 questions directly from Article 230, especially on conductor sizing, disconnect ratings, and clearances.

Defining the Parts of a Service

• Service drop (overhead) or service lateral (underground): utility-owned conductors from the transformer to the premises.
• Service-entrance conductors: the conductors on the load side of the service point that run to the service equipment.
• Service equipment: the disconnecting means, overcurrent devices, and metering, together in approved enclosures.

The service point is the boundary between utility and premises wiring; everything past it falls under NEC jurisdiction.

Number of Services (230.2)

The general rule in 230.2 is that a building or structure shall be supplied by only one service. Additional services are permitted only under four exception categories:

When more than one service supplies a building, 230.2(E) requires a permanent plaque or directory at each disconnect location identifying all other sources and the area served.

Service Conductor Sizing (230.42)

230.42(A) requires ungrounded service conductors to have an ampacity not less than the larger of:

1. 125% of continuous loads + 100% of noncontinuous loads, based on the equipment temperature rating per 110.14(C)(1) and Table 310.16, before correction/adjustment; or
2. The rating of the service disconnecting means per 230.79.

The grounded (neutral) conductor per 230.42(C) must carry the maximum unbalanced load per 220.61 and be not smaller than required by 250.24(D).

Service Disconnect Location and Number (230.70, 230.71)

230.70(A) requires a means to disconnect all ungrounded service conductors, located at a readily accessible location either outside the building or inside nearest the point of entrance of the service conductors. There is no fixed inside distance in the code text; the disconnect must simply be as close as practicable to the entry point.

230.71 limits the number of service disconnects. A 2020 NEC change removed the permission for single-pole devices with handle ties as service disconnects. Under 230.71(B), two to six disconnects are permitted per service, grouped, and each must be marked as a service disconnect. If you have two services, you can have up to 12 disconnects total (six per service).

Service Disconnect Minimum Ratings (230.79)

The disconnect rating must be not less than the calculated load per Article 220, and in no case less than:

The 100 A dwelling minimum in 230.79(C) is a frequent exam trap; the 60 A minimum applies to everything else, including multi-family and commercial.

Overhead Service Clearances

230.24(B) vertical clearances above grade for service conductors up to 150 V to ground:

• 10 ft at the service entrance, drip loop, and over areas accessed by pedestrians only.
• 12 ft over residential property and driveways, and commercial areas not subject to truck traffic.
• 18 ft over public streets, alleys, roads, or parking areas subject to truck traffic.

230.24(A) requires 8 ft above roofs, maintained for 3 ft from the roof edge; reduced to 3 ft where the roof slope is 4 in 12 or greater.

230.26 requires the point of attachment to be not less than 10 ft above finished grade, raised higher if needed to maintain 230.9 and 230.24 clearances.

230.28 governs service masts: they must have adequate mechanical strength or be braced/guyed, and conductors must not be attached between a coupling and the weatherhead.

Underground Service Lateral (230.30, 230.31)

230.30 and 230.31 cover underground service-entrance conductors, requiring direct-burial cable or raceway approved for the condition, with minimum burial depths per 300.5(D) (typically 24 in for direct-buried cable, 18 in for PVC conduit).

Worked Scenario: Sizing a Dwelling Service Entrance

A 2,500 sq ft one-family dwelling has a calculated load per Article 220 of 185 A. Size the service conductors and disconnect.

Step 1 — Disconnect rating (230.79). A one-family dwelling minimum is 100 A 3-wire. The calculated load is 185 A, so the disconnect must be at least 185 A; the next standard size is 200 A.

Step 2 — Conductor ampacity (230.42). Service conductor ampacity must be not less than 125% of continuous + 100% of noncontinuous (assume no continuous load here, so the load is 185 A) and not less than the 200 A disconnect rating. Using 75 °C column of Table 310.16, 4/0 AWG aluminum is rated 180 A (too small); 250 kcmil aluminum is rated 205 A and meets the 200 A requirement.

Step 3 — OCPD. The service overcurrent device per 230.90 must not exceed conductor ampacity. A 200 A main breaker with 250 kcmil Al conductors is compliant.

Exam Traps

• 230.79(A) vs (C): Do not pick 60 A for a dwelling; the one-family dwelling minimum is 100 A. The 60 A "all other" minimum applies to non-dwellings.
• 230.71 handle-tie rule: A 2020 change removed single-pole devices with handle ties as a valid service disconnect. Each disconnect must be a listed device.
• Clearance at drip loop: 10 ft applies to the drip loop at the service entrance for 120/240 V; 12 ft applies over residential driveways, not at the entrance.
• 230.2(E) plaque: Additional services require a directory at each disconnect, not just at the main.