Service Entrance Repair: Mast, Weatherhead, and Meter Base Issues

The service entrance is the point where the utility grid connects to a building's electrical system — encompassing the weatherhead, service mast, and meter base as distinct but interdependent components. Damage or degradation at any of these three points can compromise the safety and continuity of power delivery to an entire structure. Because this equipment sits at the boundary between utility-owned and customer-owned infrastructure, repair work involves both regulatory jurisdiction and physical coordination with the serving utility. This page covers definitions, failure modes, common repair scenarios, and the decision boundaries that determine who does what work and when.

Definition and scope

The service entrance assembly connects utility overhead or underground supply conductors to the building's main distribution panel. For overhead services — still the predominant configuration in residential construction across the United States — three elements form the critical assembly:

• Weatherhead (service head): The conduit fitting at the top of the service mast through which service entrance conductors exit the building and loop up to meet utility drop wires. It is designed to shed water and prevent moisture from traveling down into the conduit.
• Service mast: The rigid metal conduit (typically 2-inch rigid steel or intermediate metal conduit) that runs vertically up the exterior wall and supports the weatherhead. It must be structurally capable of supporting conductor tension and, in many jurisdictions, withstand wind loads specified by local amendments to the National Electrical Code (NEC).
• Meter base (meter socket): The utility-facing enclosure that accepts the utility meter. It houses current transformer connections, meter jaws, and the line-side terminals. Jurisdiction over this component is typically split: the socket enclosure is customer property, but the meter itself and the seal on the enclosure are utility property.

The NEC, published by the National Fire Protection Association (NFPA) and adopted into law by state and local jurisdictions, governs service entrance conductor sizing, clearance requirements, and installation methods under Article 230. The current adopted edition is NFPA 70-2023 (effective 2023-01-01), superseding the 2020 edition. The Occupational Safety and Health Administration (OSHA) sets work-practice standards for qualified electrical workers who must de-energize or work near energized conductors at the service point.

For a broader view of where the service entrance fits within the full electrical distribution hierarchy, see the electrical systems types overview.

How it works

Utility service enters at the weatherhead and travels through the service mast as three conductors — two ungrounded (hot) legs and one grounded neutral — in a typical 120/240V residential single-phase system. These conductors terminate at the meter base's line-side lugs. After passing through the meter, they exit at the load-side lugs and continue through a service entrance cable or conduit to the main disconnect or service panel.

NEC Article 230.24 (NFPA 70-2023) specifies minimum clearance heights for service drop conductors: 10 feet above finished grade in pedestrian areas, 12 feet over residential driveways, and 18 feet over public streets. Violations of these clearances — whether from a sagging utility drop or a mast that has shifted — constitute a code deficiency that requires correction before utility reconnection.

The structural integrity of the mast is load-bearing in a specific sense: service drop conductors exert lateral and downward tension, and a mast that is inadequately supported at the roof penetration point can pull away, creating open gaps that admit water and can sever conductors. NEC Article 230.28 (NFPA 70-2023) requires that the mast and its supporting hardware be adequate to withstand the mechanical strain of the service drop.

Common scenarios

Failures at the service entrance cluster into four primary categories:

1. Mast displacement or breakage: Storm damage, vehicle impact, or corrosion-related structural failure causes the mast to lean, crack, or separate from the structure. This is the most physically visible failure mode and almost always requires a utility disconnection before repair can begin, because the weatherhead and drop wires remain energized by the utility up to and including the service head.

2. Weatherhead deterioration: Plastic or nylon weatherheads crack under UV exposure and thermal cycling. A compromised weatherhead allows water infiltration, which can wick down service entrance conductors into the meter base and panel. Evidence of this failure often appears first as corrosion on meter base terminals or unexplained tripping in the main panel — symptoms also covered in the common electrical system faults reference.

3. Meter base damage: The meter socket can sustain arc damage if the meter is pulled while energized, or physical damage from impact. Corroded or burned meter jaw contacts increase resistance, causing localized heating. Because the line-side of the meter base is energized directly from the utility, meter base replacement requires a utility-issued disconnect (a meter pull) and, in most jurisdictions, a permit and inspection before the utility will re-meter.

4. Conductor insulation failure: Service entrance conductors exposed above the weatherhead are utility responsibility; conductors inside the conduit are the customer's. Insulation on the customer-side conductors degrades over decades, particularly when older rubber-insulated conductors were used. A formal comparison is relevant here: Type SE cable (service entrance cable, unarmored) is used in many older installations and is susceptible to outer jacket cracking, while Type SER and SEU variants have differing neutral configurations — SER includes a bare neutral suitable for subpanel feeds, SEU has a concentric neutral wrap suited to service entrance runs.

For storm-specific failure patterns, see electrical repair after storm damage.

Decision boundaries

The single most important boundary at the service entrance is the utility demarcation line: everything from the utility transformer up to and including the service drop wires and their attachment point is utility infrastructure. The weatherhead, the mast below the point of attachment, the meter base enclosure, and all conductors inside the conduit are customer-owned. This means:

1. Utility de-energization is required for any work on the mast or meter base, because the service head and drop wires remain live regardless of the position of the main breaker.
2. A permit is required in virtually all jurisdictions for service entrance repair or replacement. The electrical repair permits and inspections page covers the permit process in detail.
3. Licensed electrician requirements apply at the service entrance level in all 50 states. No jurisdiction permits unlicensed individuals to perform service entrance work. See licensed electrician repair requirements for state-level licensing structure.
4. Utility coordination is a distinct step — the electrician or property owner must contact the utility to schedule a meter pull before work begins and a re-meter inspection before power is restored. This step is separate from the municipal inspection process.
5. Inspection before re-energization is a standard requirement: the local authority having jurisdiction (AHJ) must approve the completed installation before the utility will reconnect service.

The repair-versus-replacement decision hinges on the extent of damage. A cracked weatherhead alone is a component-level repair. A mast that has separated from the structure, a meter base with burned jaws, or service entrance conductors with compromised insulation across the full run typically constitute replacement of the assembly. For structured guidance on that threshold, see the electrical repair vs replacement decision guide.

References

• National Electrical Code (NEC), NFPA 70-2023 — National Fire Protection Association
• OSHA Electrical Standards, 29 CFR 1910 Subpart S — Occupational Safety and Health Administration
• OSHA 29 CFR 1926 Subpart K — Electrical (Construction)
• NEC Article 230 — Services (via eCFR/NFPA reference)
• U.S. Consumer Product Safety Commission — Electrical Safety