Wire and cable guides

Practical guides for choosing and ordering wire and cable. Each one cites the NEC section or table it relies on, so you can check it against the edition your jurisdiction uses. Wire reference charts and calculators

• NM-B wire size by circuit: 15 to 60 amp breakers

  Which NM-B gauge goes on which breaker, why NM-B uses the 60 C column of NEC Table 310.16, and when to size up for distance or heat.

  Published Sep 30, 2026

• THHN vs XHHW-2: which building wire to pull

  THHN/THWN-2 and XHHW-2 compared: insulation, wet ratings, pulling, conduit fill and where each one belongs, with the NEC tables behind them.

  Published Sep 30, 2026

• UF-B vs NM-B: indoor cable or underground cable

  How UF-B and NM-B differ in build, wet ratings and direct burial, the burial depths from NEC Table 300.5, and the mistakes inspectors flag.

  Published Sep 30, 2026

• Aluminum vs copper feeders: sizing, cost and terminations

  Copper and aluminum feeder sizes side by side from the 75 C column, the 200 A service example, and how to terminate aluminum so it lasts.

  Published Sep 30, 2026

• Voltage drop: a worked example with NEC Chapter 9, Table 8

  Calculate voltage drop by hand for a 150 ft, 16 A run, see how each wire size compares, and learn when moving to 240 V beats buying bigger wire.

  Published Sep 30, 2026

• How to read the markings on a wire jacket

  What each part of a wire legend means: size, stranding, insulation type, voltage, listing, oil and sun ratings, file numbers and footage markers.

  Published Sep 30, 2026

• Electrical wire color code: what the NEC requires and what is convention

  Neutral, ground and hot conductor colors under the NEC, the 120/208 V and 277/480 V conventions, re-marking large conductors and posting rules.

  Published Sep 30, 2026

• Underground wire: which types to use and how deep to bury them

  UF-B, USE-2, URD and conductors in conduit for underground runs, with the minimum cover depths from NEC Table 300.5 and the rules around them.

  Published Sep 30, 2026

• SOOW vs SJOOW: choosing portable cord

  What the letters in SOOW, SJOOW, SEOOW and SJTOW mean, which voltage and duty each suits, and where the NEC says cord cannot go.

  Published Sep 30, 2026

• Welding cable sizing: amps, lead length and voltage drop

  Size welding leads by output current, duty cycle and total circuit length, check the size by voltage drop, and choose Class K or Class M.

  Published Sep 30, 2026

• How much wire to order: a quick takeoff

  Measure the route, add the box and panel allowances from NEC 300.14, multiply by conductors, and decide between a cut and a full spool.

  Published Sep 30, 2026

• MC vs AC cable: grounding, where each is allowed and fittings

  MC and AC armored cable compared under NEC Articles 330 and 320: the grounding path, the AC bonding strip, wet locations, support, fittings and cost.

  Published Sep 30, 2026

• SER vs SEU cable: service entrance or feeder

  SER and SEU compared under NEC Article 338: the bare or insulated neutral, when each may feed a subpanel, and sizing with 310.12 and Table 310.16.

  Published Sep 30, 2026

• URD vs USE-2: cabled or single conductors for underground runs

  URD and USE-2 compared for direct burial: cabled versus single conductors, service laterals, neutral marking and the burial depths in NEC Table 300.5.

  Published Sep 30, 2026

• GXL vs TXL vs SXL: automotive primary wire compared

  SAE J1128 primary wire compared: wall thickness, cross-linked insulation, temperature range, connector seals and where GXL, TXL, SXL and GPT belong.

  Published Sep 30, 2026

• Welding cable vs battery cable: stranding, jackets and uses

  Class K and M welding cable against SAE J1127 battery cable: stranding, flexibility, jackets, ratings, lugs, and why welding cable is not building wire.

  Published Sep 30, 2026

• PV wire vs USE-2: which conductor goes in a solar array

  PV wire and USE-2 compared under NEC 690.31: UL 4703 and 2 kV ratings, sunlight resistance, functionally grounded arrays and the rules by NEC edition.

  Published Sep 30, 2026

• Cat6 vs Cat6A: bandwidth, 10 gigabit distance, PoE and fire ratings

  Cat6 and Cat6A compared: 250 vs 500 MHz, 10GBASE-T at 55 m or 100 m, diameter, shielding, PoE heat in bundles and CMR or CMP listings under the NEC.

  Published Sep 30, 2026