Editing National Electrical Code (section)

==Requirements==
Article 210 addresses "branch circuits" (as opposed to service or feeder circuits) and receptacles and fixtures on branch circuits.Electrical Construction and Maintenance Magazine, Branch Circuits, Part 2. There are requirements for the minimum number of branches, and placement of receptacles, according to the location and purpose of the receptacle outlet.  Ten important items in Article 210 have been summarized in a codebook.<ref>[http://www.codebookcity.com/codearticles/nec/necarticle210.htm National Electrical Code Top Ten Tips: Article 210, Branch Circuits<!-- Bot generated title -->]</ref>

Feeder and branch circuit wiring systems are designed primarily for [[Copper wire and cable|copper conductors]]. [[Aluminum wiring]] is listed by [[Underwriters Laboratories]] for interior wiring applications and became increasingly used around 1966 due to its lower cost. Prior to 1972, however, the aluminum wire used was manufactured to conform to the 1350 series aluminum alloy, but this alloy was eventually deemed unsuitable for branch circuits due to [[galvanic corrosion]] where the copper and aluminum touched, resulting in poor contact and resistance to current flow, connector overheating problems, and potential fire risk. Today, a new aluminum wire (AA-8000) has been approved for branch circuits that does not cause corrosion where it contacts copper, but it is not readily available and is not manufactured below size #8 AWG. Hence, [[Copper wire and cable|copper wire]] is used almost exclusively in branch circuitry.

A [[Residual-current device|ground fault circuit interrupter]] (GFCI) is required for all receptacles in wet locations defined in the Code.  The NEC also has rules about how many circuits and receptacles should be placed in a given residential dwelling, and how far apart they can be in a given type of room, based upon the typical cord length of small appliances.

[[File:PolarizedOutlet.svg|right|frame|Polarized, grounding, 120 Volt receptacle]]

During [[World War II]] it was permitted for the cases of some specially ''listed'' fix-wired appliances, including [[kitchen stove]]s (ranges; ovens), [[cook top]]s, and [[clothes dryer]]s, to be grounded through their neutral conductor as a measure to conserve copper. This practice was removed in the 1996 edition, but existing installations (called "old work") may still allow this to remain in place.{{Citation needed|date=June 2025}}

As of 1962, the NEC required that new 120 Volt household receptacle outlets, for general purpose use, be both ''[[Ground (electricity)|grounded]]'' and ''polarized''.  [[National Electrical Manufacturers Association|NEMA]] connectors implement these requirements.

The NEC also permits grounding-type receptacles in non-grounded wiring protected by a GFCI; this only applies when old non-grounded receptacles are replaced with grounded receptacles, and the new receptacles must be marked with 'No equipment ground' and 'GFCI Protected' .  [[File:220sb.svg|left|170px|thumb|240&nbsp;V receptacle faces]]
The 1999 Code required that new 120/240 volt receptacles, such as those for electric ranges and dryers, be grounded also, which necessitates a fourth slot in their faces.  Changes in standards often create problems for new work in old buildings.
[[File:Leviton Dual Function AFCI GFCI Receptacle.jpg|thumb|A 120 volt combination AFCI/GFCI receptacle|330x330px]]
Unlike circuit breakers and fuses, which only open the circuit when the current exceeds a fixed value for a fixed time, a GFCI device will interrupt electrical service when more than 4 to 6 milliamperes of current in either conductor leaks to ground. A GFCI detects an imbalance between the current in the "hot" side and the current in the "neutral" side.  One GFCI receptacle can serve as protection for several downstream conventional receptacles.  GFCI devices come in many configurations including circuit-breakers, portable devices and receptacles.

Another safety device introduced with the 1999 code is the [[arc-fault circuit interrupter]] (AFCI).  This device detects arcs from hot to neutral that can develop when insulation between wires becomes frayed or damaged.  While arcs from hot to neutral would not trip a GFCI device since current is still balanced, circuitry in an AFCI device detects those arcs and will shut down a circuit.  AFCI devices generally replace the circuit breaker in the circuit. As of the 1999 National Electrical Code, AFCI protection is required in new construction on all 15- and 20-amp, 125-volt circuits to bedrooms.<ref>{{Cite web|url=http://www.afcisafety.org/codes.html|title=AFCISafety.org|website=www.afcisafety.org|access-date=2016-03-28}}</ref>

===Conduit and cable protection===
The NEC requires that conductors of a circuit must be inside a raceway, cable, trench, cord, or cable tray. Additional protection such as NM cable inside raceway is needed if the installation method is subjected to physical damage as determined by the authority having jurisdiction.

The NEC sets three general requirements that PVC conduit must meet to ensure safe electrical installations. These requirements include:<ref>{{Cite web |last=Ledes |first=tube |title=Understanding the NEC PVC Conduit Requirements |url=https://www.ledestube.com/understanding-the-nec-pvc-conduit-requirements/ |url-status=live |website=Ledes}}</ref>

'''1.Compliance with UL Standards:''' PVC conduit used in electrical installations must comply with the UL (Underwriters Laboratories) standards specifically designed for PVC conduit. This ensures that the conduit meets the necessary safety and performance criteria.

'''2.Environmental Suitability:''' PVC conduit must be suitable for the environment in which it will be installed. Different types of PVC conduit are available for indoor, outdoor, wet, or corrosive environments. Choosing the appropriate type ensures the longevity and reliability of the conduit system.

'''3.Marking and Identification:''' PVC conduit must bear proper markings for identification, including the manufacturer’s name or trademark, conduit size, and applicable electrical standard. These markings help in identifying the conduit and verifying its compliance with the required standards.

===Temperature rating===
The temperature rating of a wire or cable is generally the maximum safe ambient temperature that the wire can carry full-load power without the cable insulation melting, oxidizing, or self-igniting. A full-load wire does heat up slightly due to the metallic resistance of the wire, but this wire heating is factored into the cable's temperature rating. (NEC 310.10)<ref name="table 310 reference and details">{{cite web |title=Temperature Limitations of Connections Must Not Be Exceeded |url=https://www.ecmag.com/section/codes-standards/temperature-limitations-connections-must-not-be-exceeded |website=Electrical Contractor Magazine |language=en}}</ref>

The NEC specifies acceptable numbers of conductors in crowded areas such as inside conduit, referred to as the ''fill rating''. If the accepted fill rating is exceeded, then all the cables in the conduit are ''derated'', lowering their acceptable maximum ambient [[operating temperature]]. Derating is necessary because multiple conductors carrying full-load power generate heat that may exceed the normal insulation temperature rating. (NEC 310.16)

The NEC also specifies adjustments of the ampacity for wires in circular raceways exposed to sunlight on rooftops, due to the heating effects of solar radiation. Electrical Construction and Maintenance Magazine, Conductors for General Use,  Chapter 3 Articles in NEC, starting with Article 342 This section is expected to be modified to include cables in future editions.

In certain situations, temperature rating can be higher than normal, such as for [[knob-and-tube wiring]] where two or more load-carrying wires are never likely to be in close proximity. A knob-and-tube installation uses wires suspended in air. This gives them a greater heat dissipation rating than standard three-wire [[Thermoplastic-sheathed_cable#North_America|NM-2 cable]], which includes two tightly bundled load and return wires.<ref name="nm cable specifications">{{cite web |title=334.30 Securing and Supporting. |url=https://www.electricallicenserenewal.com/Electrical-Continuing-Education-Courses/NEC-Content.php?sectionID=891.0 |website=ElectricalLicenseRenewal.com}}</ref>