Data cable: Cat5e, Cat6 and Cat6A in Ohio

What separates the categories

Cat5e carries four twisted pairs of 24 gauge copper and is rated for the applications it was designed around. Cat6 uses slightly heavier conductors and adds a plastic spline between the pairs to hold separation, which buys headroom at higher frequencies. Cat6A goes further again: heavier copper, tighter pair geometry, and in most constructions an overall shield, which is why it is stiffer to pull and harder to terminate.

The practical difference in a surplus lot is weight and handling. Cat6A boxes are heavier, the cable does not coil as tightly, and a partly used box of it is more likely to have a kink near the payout than a box of Cat5e. Shielded Cat6A also needs shielded jacks and proper bonding, so a lot of it is only useful to someone set up for it.

Plenum and riser ratings

CMP is the plenum rating, for cable run in the air-handling space above a ceiling, and it uses a jacket compound formulated to limit smoke and flame spread in that space. CMR is the riser rating, for vertical runs between floors in a shaft. CM is general purpose. The rating is printed on the jacket, and it decides where the cable can legally go.

A plenum box is worth more than the same box in general purpose, because plenum cable is what a commercial fit-out actually specifies. It is also the rating most likely to be left over, since a contractor buys plenum for the ceiling and general purpose for the risers, and the two do not get used up at the same rate.

Boxes, part boxes and what is inside them

Data cable ships in 1,000 foot boxes, pulled through a payout hole with a counter on some designs. A sealed box with an intact tape line is a product and needs no measuring. An opened box needs the remaining length established, and the honest way to do that is to pull it out and measure rather than to guess from the coil size.

Water is the quiet killer. Boxes stored on a concrete floor in a humid space take moisture through the cardboard, and the cable inside takes it at the cut end. Sun on a box left in a trailer for a season will fade the print and stiffen the jacket. Neither shows from the outside unless someone opens the box.

• Box sealed with original tape line intact
• Category and rating legible on the jacket print
• Solid copper conductors, not copper-clad aluminum
• No water staining on the box or the coil
• Remaining length measured, not estimated

Where the surplus comes from in Ohio

Office fit-outs in Columbus and the northern suburbs leave part boxes behind constantly, because the design changes after the cable is ordered and the contractor keeps what is left rather than returning it. The data-center corridor around Newark and the Licking County industrial parks generates larger quantities in one go, often in full boxes of one color that were never opened.

Color matters more than people expect. Blue and white move quickly; an unusual color ordered for a tenant standard may sit. A lot sorted by color and category is straightforward to review. A pallet of mixed boxes with the tape broken on half of them is a counting job before it is anything else.