We buy NM-B / Romex.

What NM-B is rated for, and what it is not

NM-B is a 600 V non-metallic sheathed cable: two or three insulated conductors plus a bare ground, wrapped in a paper separator and a PVC jacket, with the conductors running flat. It is a dry-location cable. It does not belong in wet locations, in buried conduit, or outdoors in sunlight, and the 90 degree insulation rating does not permit 90 degree ampacity.

That matters when cable comes back from a job. NM-B that was pulled into an exterior run and removed, or that sat in a puddle behind a shed, is judged on whether water reached the paper wrap. Peel the jacket back six inches at the end. Damp paper and dull copper mean the length is a metal lot, not a re-usable coil.

Where the coils accumulate

Service electricians are the steadiest source. A rewire uses part of a coil, the rest goes back in the van, and after a month there are eight partial coils of 12/2 and 14/2 rolling around under the shelving. When the van is cleaned out or the business changes hands, that pile becomes a lot, and it usually arrives in a single visit.

Builders and production crews leave the larger material. A subdivision phase that finishes short leaves unopened 1,000 foot reels of 14/2 and 12/2 still banded, and a plan change can strand a reel of 6/3 that nobody wants to store. Add the coils from a kitchen remodel or a garage addition, and the volume adds up across a metro area this size.

The third source is the least tidy: a house that was rewired in stages. An owner adds a circuit, then a feed to a detached garage, then a generator inlet, and each visit leaves another open coil in the attic. That material is usually older, hand-wrapped and dusty, and it is still worth listing if the sizes are useful.

• Partial coils of 14/2 and 12/2 from service vans
• Unopened 250 foot coils from a closed-out phase
• 1,000 foot reels of 14/2, 12/2 and 10/2
• 6/3 and 4/3 from range, dryer and subpanel runs
• Three conductor coils in 14/3 and 12/3
• Mixed coils from remodel and addition work

Coils that have been re-wrapped by hand are fine. Say so if the wrap is loose, because a coil that opens in transit is harder to measure.

The honest ceiling on NM-B value

NM-B is the least expensive cable in the building, and that shapes what a used lot is worth. A coil is competing with new stock on the shelf, so the review looks at whether the length is meaningful, whether the jacket is clean, and whether the cable is still on its original wrap. Short coils of 14/2 rarely justify a dedicated trip.

The sizes that rise above that are the larger ones. 6/3 and 4/3 carry enough copper per foot to matter, and a partial reel of either is reviewed closely. Mixed small coils are still bought, but as a group, and often alongside other material from the same yard. A 6/3 reel from a range or subpanel run is the piece most likely to be asked about twice, because it is a size a remodelling crew can use again.

• Conductor size, with 6/3 and 4/3 carrying the most weight
• Remaining length, measured rather than estimated
• Jacket condition, with no splits, staples or paint
• Whether the coil is original wrap or hand re-wrapped
• Copper condition at the cut end

A coil that has been used as a drop light extension or left in a truck bed for a year is graded on metal, not on length.

Sending a coil, a pallet or a truckload

For a van clean-out, list the sizes and a rough length for each coil, and photograph them as a group on the ground. Nobody expects a partial coil to be measured to the foot. For builder overstock, the reel tags and the banding do most of the work, so photograph each reel with its tag legible.

If the material is at a jobsite, say whether the site is still active and who can open the gate. Coils stored in a connex or a model home garage are easy to collect. Coils in an attic are a different job, and it helps to know that before a truck is sent.