downlead

A downlead is a vertical or near-vertical electrical conductor that carries current from an elevated source, typically a utility pole, rooftop, or aerial service line, down to the entry point of a building or distribution equipment at ground level or below. It bridges the gap between the supply infrastructure and the premises installation, making it the physical handoff point where utility responsibility often ends and customer responsibility begins.

In utility work, downleads are sized according to the load they must carry. A residential service downlead might be 3/0 or 4/0 AWG copper or aluminum, typically 25 to 100 amperes, while industrial installations can require multiple cables of much larger cross-section. The conductor is usually insulated with PVC, XLPE, or rubber, rated for the voltage and environment. Downleads must be mechanically protected where they pass through walls or over sharp edges, often housed in conduit, raceways, or cable armor.

Routing and support are critical to downlead performance. The cable must be secured to the structure at regular intervals, typically every 1 to 2 meters for rigid conduit, and more frequently for unsupported cable. Tension, UV exposure, wind load, and temperature cycling all stress the downlead, so slack is intentionally built in at connection points. In wet or corrosive environments, materials must resist degradation; stainless steel hardware and UV-resistant jackets become essential rather than optional.

Downleads fail when they are undersized for actual demand, poorly supported and subject to mechanical strain, or left unprotected against weather and ultraviolet radiation. Corrosion at terminations is common, especially where dissimilar metals meet without proper transition fittings. Moisture ingress into cable joints leads to tracking and eventual short circuits. Poor grounding of the downlead sheath or armor can result in stray currents and touch voltage hazards.

The term itself reflects utility terminology: the lead (conductor) that goes down from the supply source. It is sometimes called a service drop where the cable is suspended in air, and service entrance where it enters the building, but downlead is the general term for the conductor itself regardless of route. Understanding the downlead's role, structural, electrical, and legal, is essential for anyone inspecting, maintaining, or upgrading electrical service infrastructure.