Paralleling large feeders: what surplus sets are worth

Above a certain size a single conductor stops being practical: too stiff to pull, too hard to terminate, too much metal in one place. So the design splits the run into parallel conductors per phase, each sized to share the load evenly across the whole set.

A surplus set is only useful to the next project if the lengths and phasing still line up. We review those lots on match rather than on tonnage, and the paperwork is what proves the match, which is why a phase list matters more than a weight ticket.

Why the run is split into parallels

Two, three or four conductors per phase let a service reach a capacity no single cable could carry through a practical duct bank. They also let a crew pull smaller, more flexible cable through bends that one large conductor would never survive.

The set behaves as one conductor electrically. That is the point of it, and it is also the weakness of a surplus set, because the moment the conductors stop matching, the set stops being a set and becomes four reels of cable that happen to share a shelf.

Equal length, equal resistance, and what breaks a set

Current divides between parallel conductors in inverse proportion to their impedance. Different lengths mean different resistance, and the shorter conductor carries more of the load. That is why the design calls for equal length and why a matched set deserves to stay together.

A set gets broken when one reel goes to another job, when a tail is cut off a single conductor, or when the reels are separated in storage and the numbering is lost. Two matched reels and one short one are not a set. They are three partial reels.

Phasing, tags and reel numbers

Record the phase against each reel: A, B, C and neutral, with the reel number beside it. Note the tagged length, the counter if there is one, and whether the conductor was ever pulled. A photograph of each tag plus a written phase list is the whole file.

Before treating cut feeders as a set, a buyer will check the tags against the list, measure what is left, and look at the cut ends for corrosion or water. Where the numbers do not line up, the material is reviewed as individual lengths and the set advantage disappears.

The big services in this region run in parallel. Data center shells east of the airport, hospital additions in Round Rock, campus work at UT Austin and Texas State, and the industrial loads along SH-130 all use multiple conductors per phase.

That means surplus parallel sets turn up here more often than in a smaller market, usually at the end of a package when the phase count changed or a service was resized. We review them across Travis, Williamson and Hays counties, matched reels first and singles after.