Low voltage cable: 600 V and below as one family

What the term covers on a plant floor

In plant language, low voltage means anything at or below 600 volts, as distinct from the medium voltage distribution that feeds the building. It takes in branch circuits, feeders, motor leads, control wiring, fire alarm cable and the building cable inside the walls. Class 2 wiring below 50 volts sits inside the same family in most people's usage.

The term is not a code classification and it does not describe a construction. Two reels in a low voltage lot may have nothing in common except a voltage rating. That is the first thing to establish when a plant says it has a pile of low voltage cable: what is actually in the pile.

Three groups inside one pile

Power cable is the first group: single and multiconductor building wire, feeder cable, tray cable, the heavy copper and aluminium that carries current to loads. It is identified by size and by the building wire type printed on the jacket. Within that group the sizes run from 14 AWG branch wire to 500 kcmil feeder, so the size range is worth stating before anything else about the pile.

Control cable is the second: multiconductor, smaller gauge, numbered or colour-coded, often shielded, used for switching and interlocks rather than for power. Instrumentation and thermocouple extension form a third group with their own pair constructions and shields. Those three groups have different buyers, so a pile that is not separated is a pile that will sit.

The order of the sort

Separate first by shield presence, because a shielded cable and an unshielded one of the same size are different products. Then by conductor count, then by gauge, then by jacket type. Doing it in that order means each pile can be described with a single line rather than a paragraph.

Lorain's plant liquidation work produces exactly this problem. A multi-building plant that ran from the 1950s to the 2010s has cable from four different eras in the same storage room, and the era shows in the jacket material more reliably than in any label.

• Shielded and unshielded separated first
• Conductor count and gauge, listed per group
• Jacket type and any printed building wire designation
• Copper or aluminium, never mixed on one pallet
• Tagged reels kept whole rather than broken into the pile

What kills a mixed low voltage lot

The failures are predictable. Unlabelled coils with no print on the outer wrap. Short cut-offs from a panel change mixed in with reel stock. Aluminium and copper on the same pallet. Water damage at the bottom layer of a stack that stood on a concrete floor for a decade.

None of those are fatal on their own, and all of them slow a review down. The version that is fatal is a pile described only by weight, because weight tells a buyer nothing about whether the cable inside can be sold as cable at all.