Buying MC cable out of ceiling grids and plant rooms.

Office and retail demolition produces whips, and whips are short. A run from a junction box to a fixture might be six feet, and the same building will hold hundreds of them, coiled and taped by whoever pulled them down. Long lengths usually mean a feeder or a riser, not a lighting circuit. Older buildings hand over the earlier armoured construction instead, which is covered under AC cable.

Data centre and plant work produces the opposite: cut-offs from tray transitions and equipment feeds, often twenty or thirty feet, still straight and still carrying a legible print. The two kinds of lot are separated at review because they behave differently on a scale.

The armour is the part that fails first. Interlocked strip crushes when a lift drops a bundle, kinks when a coil is dragged across a curb, and opens at the seam when cable is pulled hard around a corner. A crushed section can be cut out, which shortens the length, so the damage is measured in feet lost.

Rust is the other common mark on a removed lot. Damp ceiling voids and roof leaks leave the strip discoloured, and while surface rust on the outside is mostly a description, corrosion between the interlock and the conductors underneath is a condition point a buyer will want photographed.

• Closed interlock along the full length, with no seam opened by pulling.
• No crush marks, no hard kinks, no flattening from a forklift or a bundle dropped off a lift.
• Cut ends square and taped, so the conductors have not been dragged back inside the armour.
• Print legible on at least part of each length, with conductor count confirmed at the end.

Most MC in DFW carries copper THHN, and the conductor count is what a buyer counts first: two, three or four conductors plus a grounding path. Some constructions include a green insulated grounding conductor, others rely on the armour, and the difference changes how a length can be used again.

Aluminium-armour MC is a separate case. The armour is lighter, the bonding path is different, and a buyer will want to know which variant a coil is before it is weighed, since it cannot be assumed from the outside that every coil in a cart is the same construction.

Keep coils of different conductor counts in separate bundles. A cart of mixed two- and three-conductor whips takes twice as long to review and is described as mixed.

Short lengths are counted and bundled rather than weighed one at a time. A buyer will sort by conductor count, count the pieces, measure a sample and estimate the rest, then describe the lot as a count of whips with an average length, which is more honest than a single footage figure nobody can check.

If the whips are already coiled and taped, leave them that way. Uncoiling to measure every piece adds hours to a visit and gains very little, and a bundle that has been opened and re-tied in the rain is worse off than one that was left alone.