REFERENCE
Plain-English definitions of every term used in the WireFillChart calculators and charts. Each entry cites the NEC section where the term is defined.
ALL REFERENCE
- 01READ →
What is a Current-Carrying Conductor (CCC)?
A current-carrying conductor is a phase or neutral conductor counted under NEC 310.15(C)(1) for ampacity adjustment.
- 02READ →
What is an Equipment Grounding Conductor (EGC)?
An EGC is the conductive path that bonds non-current-carrying metal parts to the source, sized per NEC 250.122 and qualified per NEC 250.118.
- 03READ →
What is AWG (American Wire Gauge)?
AWG is the standardized US wire-sizing system. Each gauge number represents the conductor diameter — smaller numbers mean larger conductors.
- 04READ →
What is Conduit Fill Percentage?
Conduit fill is the percentage of a conduit's interior cross-section occupied by conductors. NEC caps it at 53%/31%/40% by conductor count.
- 05READ →
What is Conduit Jam Probability?
Conduit jam is the wedging that occurs when 3+ identical cables pull through conduit at a critical inside-to-outside diameter ratio between 2.8 and 3.2.
- 06READ →
What is EMT Conduit?
EMT (Electrical Metallic Tubing) is a thin-wall galvanized steel raceway, the most common conduit in US commercial wiring, covered by NEC Article 358.
- 07READ →
What is ENT (Electrical Nonmetallic Tubing)?
ENT is corrugated blue 'smurf tube' PVC for concealed dry-location wiring, governed by NEC Article 362. Building height limits apply.
- 08READ →
What is Flexible Metal Conduit (FMC)?
FMC, also called Greenfield, is spiral-wound steel conduit for short flexible connections, governed by NEC Article 348. Limited as EGC over 6 ft.
- 09READ →
What is IMC (Intermediate Metal Conduit)?
IMC is intermediate-wall threaded steel conduit, lighter than RMC with more interior fill area, permitted in all RMC uses under NEC Article 342.
- 10READ →
What is kcmil and How is it Used?
kcmil = thousands of circular mils, the US unit for conductor cross-sectional area above 4/0 AWG. Used for 250, 300, 400, 500, 750, and 1000-size feeders.
- 11READ →
What is LFNC (Liquidtight Flexible Nonmetallic Conduit)?
LFNC is liquidtight flexible nonmetallic conduit (Types A, B, C) for wet, oily, and outdoor flexible connections, governed by NEC Article 356.
- 12READ →
What is PVC Schedule 40 Conduit?
PVC Schedule 40 is rigid gray plastic conduit for underground and concealed wiring, governed by NEC Article 352. Cheap, corrosion-proof, cannot serve as EGC.
- 13READ →
What is PVC Schedule 80 Conduit?
PVC Schedule 80 is heavy-wall rigid PVC raceway required by NEC 352.10(B) where exposed conduit is subject to physical damage. Same OD as Schedule 40.
- 14READ →
What is RHH and RHW Wire?
RHH, RHW, and RHW-2 are rubber-insulated building wires used in branch circuits and feeders. NEC Article 310 and Table 5 govern dimensions and ampacity.
- 15READ →
What is RMC (Rigid Metal Conduit)?
RMC is heavy-wall threaded galvanized steel raceway, the most robust metallic conduit, permitted in hazardous locations under NEC Article 344.
- 16READ →
What is THHN Wire?
THHN is Thermoplastic High Heat-resistant Nylon-coated insulated copper or aluminum building wire, rated 90°C in dry locations per NEC Article 310.
- 17READ →
What is THWN-2 Wire?
THWN-2 is Thermoplastic Heat & Water-resistant Nylon-coated wire, rated 90°C wet AND dry. Same NEC fill area as THHN.
- 18READ →
What is Wire Ampacity?
Ampacity is the maximum continuous current a conductor can carry without exceeding its insulation temperature rating, per NEC Table 310.16.
- 19READ →
What is XHHW / XHHW-2 Wire?
XHHW is cross-linked polyethylene insulated 90°C building wire. XHHW-2 adds 90°C wet rating. Same NEC fill area as THHN.