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Article 310

Conductors for General Wiring

Part I. General

  1. Scope. This article covers general requirements for conductors and their type designations, insulations, markings,
    mechanical strengths, ampacity ratings, and uses. These requirements do not apply to conductors that form an integral part of equipment, such as motors, motor controllers, and simi‐ lar equipment, or to conductors specifically provided for else‐ where in this Code.Informational Note: For flexible cords and cables, see Arti‐ cle 400. For fixture wires, see Article 402.
  2. Definitions.

Electrical Ducts. Electrical conduits, or other raceways round in cross section, that are suitable for use underground or embedded in concrete.

Thermal Resistivity. As used in this Code, the heat transfer capability through a substance by conduction.

Informational Note: Thermal resistivity is the reciprocal of ther‐ mal conductivity and is designated Rho, which is expressed in the units °C-cm/W.

Part II. Installation

310.10 Uses Permitted. The conductors described in 310.104 shall be permitted for use in any of the wiring methods covered in Chapter 3 and as specified in their respective tables or as permitted elsewhere in this Code.

  1. Dry Locations. Insulated conductors and cables used in dry locations shall be any of the types identified in this Code.
  2. Dry and Damp Locations. Insulated conductors and cables used in dry and damp locations shall be Types FEP, FEPB, MTW, PFA, RHH, RHW, RHW-2, SA, THHN, THW, THW-2, THHW, THWN, THWN-2, TW, XHH, XHHW, XHHW-2, Z, or ZW.
  3. Wet Locations. Insulated conductors and cables used in wet locations shall comply with one of the following:
    1. Be moisture-impervious metal-sheathed
    2. Be types MTW, RHW, RHW-2, TW, THW, THW-2, THHW,THWN, THWN-2, XHHW, XHHW-2, or ZW
    3. Be of a type listed for use in wet locations
  4. Locations Exposed to Direct Sunlight. Insulated conduc‐ tors or cables used where exposed to direct rays of the sun shall comply with (D)(1) or (D)(2):
    1. Conductors and cables shall be listed, or listed and marked, as being sunlight resistant
    2. Conductors and cables shall be covered with insulating material, such as tape or sleeving, that is listed, or listed and marked, as being sunlight resistant
  5. Shielding. Nonshielded, ozone-resistant insulated conduc‐ tors with a maximum phase-to-phase voltage of 5000 volts shall be permitted in Type MC cables in industrial establishments where the conditions of maintenance and supervision ensure that only qualified persons service the installation. For other establishments, solid dielectric insulated conductors operated above 2000 volts in permanent installations shall have ozone- resistant insulation and shall be shielded. All metallic insula‐ tion shields shall be connected to a grounding electrode conductor, a grounding busbar, an equipment grounding conductor, or a grounding electrode.Informational Note: The primary purposes of shielding are to confine the voltage stresses to the insulation, dissipate insulationleakage current, drain off the capacitive charging current, and carry ground-fault current to facilitate operation of ground-fault protective devices in the event of an electrical cable fault.Exception No. 1: Nonshielded insulated conductors listed by a qualified testing laboratory shall be permitted for use up to 2400 volts under the following conditions:
    1. Conductors shall have insulation resistant to electric discharge and surface tracking, or the insulated conductor(s) shall be covered with a material resistant to ozone, electric discharge, and surface tracking.
    2. Where used in wet locations, the insulated conductor(s) shall have an overall nonmetallic jacket or a continuous metallic sheath.
    3. Insulation and jacket thicknesses shall be in accordance with Table 310.104(D).
    Exception No. 2: Nonshielded insulated conductors listed by a qualified testing laboratory shall be permitted for use up to 5000 volts to replace existing nonshielded conductors, on existing equipment in industrial establishments only, under the following conditions:
    1. Where the condition of maintenance and supervision ensures that only qualified personnel install and service the installation.
    2. Conductors shall have insulation resistant to electric discharge and surface tracking, or the insulated conductor(s) shall be covered with a material resistant to ozone, electric discharge, and surface tracking.
    3. Where used in wet locations, the insulated conductor(s) shall have an overall nonmetallic jacket or a continuous metallic sheath.
    4. Insulation and jacket thicknesses shall be in accordance with Table 310.104(D).
    Informational Note: Relocation or replacement of equipment may not comply with the term existing as related to this excep‐ tion.Exception No. 3: Where permitted in 310.10(F), Exception No. 2.
  6. Direct-Burial Conductors. Conductors used for direct- burial applications shall be of a type identified for such use.Cables rated above 2000 volts shall be shielded.Exception No. 1: Nonshielded multiconductor cables rated 2001– 2400 volts shall be permitted if the cable has an overall metallic sheath or armor.The metallic shield, sheath, or armor shall be connected to a grounding electrode conductor, grounding busbar, or a grounding electrode.Exception No. 2: Airfield lighting cable used in series circuits that are rated up to 5000 volts and are powered by regulators shall be permitted to be nonshielded.Informational Note to Exception No. 2: Federal Aviation Admin‐ istration (FAA) Advisory Circulars (ACs) provide additional practices and methods for airport lighting.Informational Note No. 1: See 300.5 for installation require‐ ments for conductors rated 1000 volts or less.Informational Note No. 2: See 300.50 for installation require‐ ments for conductors rated over 1000 volts.
  7. Corrosive Conditions. Conductors exposed to oils, greases, vapors, gases, fumes, liquids, or other substances having a deleterious effect on the conductor or insulation shall be of a type suitable for the application.
  8. Conductors in Parallel.
    1. General. Aluminum, copper-clad aluminum, or copper conductors, for each phase, polarity, neutral, or grounded circuit shall be permitted to be connected in parallel (electri‐ cally joined at both ends) only in sizes 1/0 AWG and larger where installed in accordance with 310.10(H)(2) through (H)(6).Exception No. 1: Conductors in sizes smaller than 1/0 AWG shall be permitted to be run in parallel to supply control power to indicating instruments, contactors, relays, solenoids, and similar control devices, or for frequencies of 360 Hz and higher, provided all of the following apply:
      1. They are contained within the same raceway or cable.
      2. The ampacity of each individual conductor is sufficient to carry the entire load current shared by the parallel conductors.
      3. The overcurrent protection is such that the ampacity of each individual conductor will not be exceeded if one or more of the parallel conductors become inadvertently disconnected.Exception No. 2: Under engineering supervision, 2 AWG and 1 AWG grounded neutral conductors shall be permitted to be installed in paral‐ lel for existing installations.Informational Note to Exception No. 2: Exception No. 2 can be used to alleviate overheating of neutral conductors in existing installations due to high content of triplen harmonic currents.
    2. Conductor and Installation Characteristics. The paralleled conductors in each phase, polarity, neutral, grounded circuit conductor, equipment grounding conductor, or equipment bonding jumper shall comply with all of the following:
  1. Be the same length.
  2. Consist of the same conductor material.
  3. Be the same size in circular mil area.
  4. Have the same insulation type.
  5. Be terminated in the same manner.
  1. Separate Cables or Raceways. Where run in separate cables or raceways, the cables or raceways with conductors shall have the same number of conductors and shall have the same electrical characteristics. Conductors of one phase, polarity, neutral, grounded circuit conductor, or equipment grounding conductor shall not be required to have the same physical char‐ acteristics as those of another phase, polarity, neutral, groun‐ ded circuit conductor, or equipment grounding conductor.
  2. Ampacity Adjustment. Conductors installed in parallel shall comply with the provisions of 310.15(B)(3)(a).

310.15 Ampacities for Conductors Rated 0–2000 Volts.

  1. General.
    1. Tables or Engineering Supervision. Ampacities for conductors shall be permitted to be determined by tables as provided in 310.15(B) or under engineering supervision, as provided in 310.15(C).Informational Note No. 1: Ampacities provided by this section do not take voltage drop into consideration. See 210.19(A), Informational Note No. 4, for branch circuits and 215.2(A), Informational Note No. 2, for feeders.Informational Note No. 2: For the allowable ampacities of Type MTW wire, see Table 13.5.1 in NFPA 79-2015, Electrical Standard for Industrial Machinery.
    2. Selection of Ampacity. Where more than one ampacity applies for a given circuit length, the lowest value shall be used.Exception: Where different ampacities apply to portions of a circuit, the higher ampacity shall be permitted to be used if the total portion(s) of the circuit with lower ampacity does not exceed the lesser of 3.0 m (10 ft) or 10 percent of the total circuit.Informational Note: See 110.14(C) for conductor temperature limitations due to termination provisions.
    3. Temperature Limitation of Conductors. No conductor shall be used in such a manner that its operating temperature exceeds that designated for the type of insulated conductor involved. In no case shall conductors be associated together in such a way, with respect to type of circuit, the wiring method employed, or the number of conductors, that the limiting temperature of any conductor is exceeded.Informational Note No. 1: The temperature rating of a conduc‐ tor [see Table 310.104(A) and Table 310.104(C)] is the maxi‐ mum temperature, at any location along its length, that the conductor can withstand over a prolonged time period without serious degradation. The allowable ampacity tables, the ampac‐ ity tables of Article 310 and the ampacity tables of Informative Annex B, the ambient temperature correction factors in 310.15(B)(2), and the notes to the tables provide guidance for coordinating conductor sizes, types, allowable ampacities, ampacities, ambient temperatures, and number of associated conductors. The principal determinants of operating tempera‐ ture are as follows:
      1. Ambient temperature — ambient temperature may vary along the conductor length as well as from time to time.
      2. Heat generated internally in the conductor as the result of load current flow, including fundamental and
        1. Equipment Grounding Conductors. Where parallel equip‐ ment grounding conductors are used, they shall be sized in accordance with 250.122. Sectioned equipment grounding
          (3)harmonic currents.The rate at which generated heat dissipates into the ambi‐ ent medium. Thermal insulation that covers or surrounds conductors affects the rate of heat dissipation.conductors smaller than 1/0 AWG shall be permitted in multi‐ conductor cables, if the combined circular mil area of the sectioned equipment grounding conductors in each cable complies with 250.122.
        2. Bonding Jumpers. Where parallel equipment bonding jumpers or supply-side bonding jumpers are installed in race‐ ways, they shall be sized and installed in accordance with 250.102.
        (4) Adjacent load-carrying conductors — adjacent conductors have the dual effect of raising the ambient temperature and impeding heat dissipation.Informational Note No. 2: Refer to 110.14(C) for the tempera‐ ture limitation of terminations.
  2. Tables. Ampacities for conductors rated 0 to 2000 volts shall be as specified in the Allowable Ampacity Table 310.15(B)(16) through Table 310.15(B)(19), and Ampacity Table 310.15(B)(20) and Table 310.15(B)(21) as modified by 310.15(B)(1) through (B)(7).The temperature correction and adjustment factors shall be permitted to be applied to the ampacity for the temperature
    rating of the conductor, if the corrected and adjusted ampacity does not exceed the ampacity for the temperature rating of theTable 310.15(B)(2)(a) Ambient Temperature Correction Factors Based on 30°C (86°F)termination in accordance with the provisions of 110.14(C).                                                                                                                                Informational Note: Table 310.15(B)(16) through Table 310.15(B)(19) are application tables for use in determining conductor sizes on loads calculated in accordance with Article220. Allowable ampacities result from consideration of one or more of the following:
    1. Temperature compatibility with connected equipment, especially the connection points.Ambient Temperature (°C)Temperature Rating of ConductorAmbient Temperature (°F)60°C75°C90°C10 or less1.291.201.1550 or less11–151.221.151.1251–5916–201.151.111.0860–6821–251.081.051.0469–7726–301.001.001.0078–8631–350.910.940.9687–9536–400.820.880.9196–10441–450.710.820.87105–11346–500.580.750.82114–12251–550.410.670.76123–13156–60—0.580.71132–14061–65—0.470.65141–14966–70—0.330.58150–15871–75——0.50159–16776–80——0.41168–17681–85——0.29177–185
    2. Coordination with circuit and system overcurrent protec‐For ambient temperatures other than 30°C (86°F), multiply the allowable ampacities specified in the ampacity tables by the appropriate correction factor shown below.tion.
    3. Compliance with the requirements of product listings or certifications. See 110.3(B).
    4. Preservation of the safety benefits of established industry practices and standardized procedures.
    1. General. For explanation of type letters used in tables and for recognized sizes of conductors for the various conductor insulations, see Table 310.104(A) and Table 310.104(B). For installation requirements, see 310.1 through 310.15(A)(3) and the various articles of this Code. For flexible cords, see Table 400.4, Table 400.5(A)(1), and Table 400.5(A)(2).
    2. Ambient Temperature Correction Factors. Ampacities for ambient temperatures other than those shown in the ampacity tables shall be corrected in accordance with Table 310.15(B)(2)(a) or Table 310.15(B)(2)(b), or shall be permit‐ ted to be calculated using the following equation:
      imageT T c aT Tc a[310.15(B)(2)]
      I   I
      where:I′ = ampacity corrected for ambient temperatureI = ampacity shown in the tablesTc = temperature rating of conductor (°C)Ta′ = new ambient temperature (°C)Ta = ambient temperature used in the table (°C)
    3. Adjustment Factors.
      1. More than Three Current-Carrying Conductors. Where the number of current-carrying conductors in a raceway or cable exceeds three, or where single conductors or multiconductor cables are installed without maintaining spacing for a continu‐ ous length longer than 600 mm (24 in.) and are not installed in raceways, the allowable ampacity of each conductor shall be reduced as shown in Table 310.15(B)(3)(a). Each current- carrying conductor of a paralleled set of conductors shall be counted as a current-carrying conductor.Where conductors of different systems, as provided in 300.3, are installed in a common raceway or cable, the adjustment factors shown in Table 310.15(B)(3)(a) shall apply only to the number of power and lighting conductors (Articles 210, 215, 220, and 230).Informational Note No. 1: See Annex B for adjustment factors for more than three current-carrying conductors in a raceway or cable with load diversity.Informational Note No. 2: See 366.23 for adjustment factors for conductors and ampacity for bare copper and aluminum bars in
        auxiliary gutters and 376.22(B) for adjustment factors for conductors in metal wireways.
        1. Where conductors are installed in cable trays, the provi‐ sions of 392.80 shall apply.
        2. Adjustment factors shall not apply to conductors in race‐ ways having a length not exceeding 600 mm (24 in.).
        3. Adjustment factors shall not apply to underground conductors entering or leaving an outdoor trench if those conductors have physical protection in the form of rigid metal conduit, intermediate metal conduit, rigid polyvinyl chloride conduit (PVC), or reinforced thermosetting resin conduit (RTRC) having a length not exceeding 3.05 m (10 ft), and if the number of conductors does not exceed four.
        4. Adjustment factors shall not apply to Type AC cable or to Type MC cable under the following conditions:
        1. The cables do not have an overall outer jacket.
        2. Each cable has not more than three current-carrying conductors.
        3. The conductors are 12 AWG copper.Exception to (4): If cables meeting the requirements in310.15(B)(3)(4)a through c with more than 20 current-carrying conductors are installed longer than 600 mm (24 in.) without main‐ taining spacing, are stacked, or are supported on bridle rings, a 60 percent adjustment factor shall be applied.
        4. Not more than 20 current-carrying conductors are instal‐ led without maintaining spacing, are stacked, or are supported on “bridle rings.”

        •
      2. Raceway Spacing. Spacing between raceways shall bemaintained.
        Table 310.15(B)(2)(b) Ambient Temperature Correction Factors Based on 40ºC (104ºF)
        imageFor ambient temperatures other than 40°C (104°F), multiply the allowable ampacities specified in the ampacity tables by the appropriate correction factor shown below.Ambient Temperature (°C)Temperature Rating of ConductorAmbient Temperature (ºF)60°C75°C90°C150°C200°C250°C10 or less1.581.361.261.131.091.0750 or less11–151.501.311.221.111.081.0651–5916–201.411.251.181.091.061.0560–6821–251.321.21.141.071.051.0469–7726–301.221.131.101.041.031.0278–8631–351.121.071.051.021.021.0187–9536–401.001.001.001.001.001.0096–10441–450.870.930.950.980.980.99105–11346–500.710.850.890.950.970.98114–12251–550.500.760.840.930.950.96123–13156–60—0.650.770.900.940.95132–14061–65—0.530.710.880.920.94141–14966–70—0.380.630.850.900.93150–15871–75——0.550.830.880.91159–16776–80——0.450.800.870.90168–17681–90———0.740.830.87177–19491–100———0.670.790.85195–212101–110———0.600.750.82213–230111–120———0.520.710.79231–248121–130———0.430.660.76249–266131–140———0.300.610.72267–284141–160————0.500.65285–320161–180————0.350.58321–356181–200—————0.49357–392201–225—————0.35393–437
      3. Raceways and Cables Exposed to Sunlight on Rooftops. Where raceways or cables are exposed to direct sunlight on or above
    Table 310.15(B)(3)(a) Adjustment Factors for More Than Three Current-Carrying Conductorsrooftops, raceways or cables shall be installed a minimum                                                                                                                                distance above the roof to the bottom of the raceway or cable of 23 mm (7∕8 in.). Where the distance above the roof to the bottom of the raceway is less than 23 mm (7∕8 in.), a tempera‐ ture adder of 33°C (60°F) shall be added to the outdoor temperature to determine the applicable ambient temperature for application of the correction factors in Table
    imageNumber of Conductors1Percent of Values in Table 310.15(B)(16) ThroughTable 310.15(B)(19) as Adjusted for Ambient Temperature if Necessary310.15(B)(2)(a) or Table 310.15(B)(2)(b).Exception: Type XHHW-2 insulated conductors shall not be subject to this ampacity adjustment.Informational Note: One source for the ambient temperatures in various locations is the ASHRAE Handbook — Fundamentals.•
    1. Bare or Covered Conductors. Where bare or coveredconductors are installed with insulated conductors, the temper‐ ature rating of the bare or covered conductor shall be equal to the lowest temperature rating of the insulated conductors for the purpose of determining ampacity.
    2. Neutral Conductor.
      1. A neutral conductor that carries only the unbalanced current from other conductors of the same circuit shall not be required to be counted when applying the provisions of 310.15(B)(3)(a).
      2. In a 3-wire circuit consisting of two phase conductors and the neutral conductor of a 4-wire, 3-phase, wye-connected system, a common conductor carries approximately the same current as the line-to-neutral load currents of the other4–6 807–9 7010–20 5021–30 4531–40 4041 and above 351Number of conductors is the total number of conductors in the raceway or cable, including spare conductors. The count shall be adjusted in accordance with 310.15(B)(5) and (6). The count shall not include conductors that are connected to electrical components that cannot be simultaneously energized.
        conductors and shall be counted when applying the provisions of 310.15(B)(3)(a).
      3. On a 4-wire, 3-phase wye circuit where the major portion of the load consists of nonlinear loads, harmonic currents are present in the neutral conductor; the neutral conductor shall therefore be considered a current-carrying conductor.
    3. Grounding or Bonding Conductor. A grounding or bond‐ ing conductor shall not be counted when applying the provi‐ sions of 310.15(B)(3)(a).
    4. Single-Phase Dwelling Services and Feeders. For one- family dwellings and the individual dwelling units of two-family and multifamily dwellings, service and feeder conductors
  3. Engineering Supervision. Under engineering supervision, conductor ampacities shall be permitted to be calculated by means of the following general equation:
    imageTc TaRdc 1  Yc Rca[310.15(C)]supplied by a single-phase, 120/240-volt system shall be permit‐ ted to be sized in accordance with 310.15(B)(7)(1) through (4).For one-family dwellings and the individual dwelling units ofI 
    where:103 amperestwo-family and multifamily dwellings, single-phase feeder conductors consisting of 2 ungrounded conductors and the neutral conductor from a 208Y/120 volt system shall be permit‐ ted to be sized in accordance with 310.15(B)(7)(1) through (3).
    1. For a service rated 100 through 400 amperes, the service conductors supplying the entire load associated with a one-family dwelling, or the service conductors supplying the entire load associated with an individual dwelling unit in a two-family or multifamily dwelling, shall be permitted to have an ampacity not less than 83 percent of the serv‐ ice rating.
    2. For a feeder rated 100 through 400 amperes, the feeder conductors supplying the entire load associated with a one-family dwelling, or the feeder conductors supplying the entire load associated with an individual dwelling unit in a two-family or multifamily dwelling, shall be permitted to have an ampacity not less than 83 percent of the feeder rating.
    3. In no case shall a feeder for an individual dwelling unit be required to have an ampacity greater than that speci‐ fied in 310.15(B)(7)(1) or (2).
    4. Grounded conductors shall be permitted to be sized smaller than the ungrounded conductors, if the require‐ ments of 220.61 and 230.42 for service conductors or the requirements of 215.2 and 220.61 for feeder conductors are met.

Where correction or adjustment factors are required by 310.15(B)(2) or (3), they shall be permitted to be applied to the ampacity associated with the temperature rating of the conductor.

Tc = conductor temperature in degrees Celsius (°C)

Ta = ambient temperature in degrees Celsius (°C)

Rdc = dc resistance of 305 mm (1 ft) of conductor in micro‐ ohms at temperature, Tc

Yc = component ac resistance resulting from skin effect and proximity effect

Rca = effective thermal resistance between conductor and surrounding ambient

310.60 Conductors Rated 2001 to 35,000 Volts.

  1. Ampacities of Conductors Rated 2001 to 35,000 Volts. Ampacities for solid dielectric-insulated conductors shall be permitted to be determined by tables or under engineering supervision, as provided in 310.60(B) and (C).
    1. Selection of Ampacity. Where more than one calculated or tabulated ampacity could apply for a given circuit length, the lowest value shall be used.Exception: Where two different ampacities apply to adjacent portions of a circuit, the higher ampacity shall be permitted to be used beyond the point of transition, a distance equal to 3.0 m (10 ft) or 10 percent of the circuit length calculated at the higher ampacity, whichever is less.Informational Note: See 110.40 for conductor temperature limi‐ tations due to termination provisions.
  2. Engineering Supervision. Under engineering supervision, conductor ampacities shall be permitted to be calculated by using the following general equation:
    imageTc  Ta  Td Rdc 1  Yc Rca[310.60(B)]Informational Note No. 1: The service or feeder ratings addressed by this section are based on the standard ampacity ratings from 240.6(A).I 
    where:103 amperesInformational Note No. 2: See Example D7 in Annex D.Tc = conductor temperature (°C)Ta = ambient temperature (°C)ΔTd = dielectric loss temperature riseRdc = dc resistance of conductor at temperature TcYc = component ac resistance resulting from skin effect and proximity effectRca = effective thermal resistance between conductor and surrounding ambientInformational Note: The dielectric loss temperature rise (ΔTd ) is negligible for single circuit extruded dielectric cables rated below 46 kV.
    Table 310.15(B)(16) (formerly Table 310.16) Allowable Ampacities of Insulated Conductors Rated Up to and Including 2000 Volts, 60°C Through 90°C (140°F Through 194°F), Not More Than Three Current-Carrying Conductors in Raceway, Cable, or Earth (Directly Buried), Based on Ambient Temperature of 30°C (86°F)*

    Size AWG or kcmilTemperature Rating of Conductor [See Table 310.104(A).]
    Size AWG or kcmil60°C (140°F)75°C (167°F)90°C (194°F)60°C (140°F)75°C (167°F)90°C (194°F)
    Types TW, UF
    Types RHW, THHW, THW, THWN, XHHW, USE, ZWTypes TBS, SA, SIS, FEP, FEPB, MI, RHH, RHW-2, THHN, THHW,THW-2, THWN-2, USE-2, XHH, XHHW,XHHW-2, ZW-2
    Types TW, UF
    Types RHW, THHW, THW, THWN, XHHW, USE
    Types TBS, SA, SIS, THHN, THHW,THW-2, THWN-2, RHH, RHW-2, USE-2, XHH, XHHW, XHHW-2, ZW-2COPPERALUMINUM OR COPPER-CLAD ALUMINUM18**16**14**12**10**8—— 15203040—— 20253550141825304055——— 152535——— 203040——— 253545———12**10**8643215570859511065851001151307595115130145405565758550657590100557585100115643211/02/03/04/01251451651951501752002301701952252601001151301501201351551801351501752051/02/03/04/02503003504005002152402602803202552853103353802903203503804301701952102252602052302502703102302602803053502503003504005006007007508009003503854004104354204604754905204755205355555852853153203303553403753853954253854254354454806007007508009001000125015001750200045549552554555554559062565066561566570573575037540543545547044548552054556050054558561563010001250150017502000*Refer to 310.15(B)(2) for the ampacity correction factors where the ambient temperature is other than 30°C (86°F). Refer to 310.15(B)(3)(a) for more than three current-carrying conductors.**Refer to 240.4(D) for conductor overcurrent protection limitations.
    Table 310.15(B)(17) (formerly Table 310.17) Allowable Ampacities of Single-Insulated Conductors Rated Up to and Including 2000 Volts in Free Air, Based on Ambient Temperature of 30°C (86°F)*

    Size AWG or kcmilTemperature Rating of Conductor [See Table 310.104(A).]
    Size AWG or kcmil60°C (140°F)75°C (167°F)90°C (194°F)60°C (140°F)75°C (167°F)90°C (194°F)
    Types TW, UF
    Types RHW, THHW, THW, THWN, XHHW, ZWTypes TBS, SA, SIS, FEP, FEPB, MI, RHH,RHW-2, THHN, THHW, THW-2, THWN-2, USE-2, XHH, XHHW, XHHW-2, ZW-2
    Types TW, UF
    Types RHW, THHW, THW, THWN, XHHW
    Types TBS, SA, SIS, THHN, THHW, THW-2, THWN-2, RHH, RHW-2, USE-2, XHH, XHHW, XHHW-2, ZW-2COPPERALUMINUM OR COPPER-CLAD ALUMINUM181614**12**10**8—— 25304060—— 30355070182435405580——— 253545——— 304055——— 354560———12**10**86432180105120140165951251451701951051401651902206080951101307510011513515585115130150175643211/02/03/04/01952252603002302653103602603003504051501752002351802102402802052352703151/02/03/04/025030035040050034037542045551540544550554562045550057061570026529033035540531535039542548535539544548054525030035040050060070075080090057563065568073069075578581587078085088592098045550051553558054559562064570061567070072579060070075080090010001250150017502000780890980107011559351065117512801385105512001325144515606257107958759607508559501050115084596510701185129510001250150017502000*Refer to 310.15(B)(2) for the ampacity correction factors where the ambient temperature is other than 30°C (86°F).**Refer to 240.4(D) for conductor overcurrent protection limitations.
    Table 310.15(B)(18) (formerly Table 310.18) Allowable Ampacities of Insulated Conductors Rated Up to and Including 2000 Volts, 150°C Through 250°C (302°F Through 482°F). Not More Than Three Current-Carrying Conductors in Raceway or Cable, Based on Ambient Air Temperature of 40°C (104°F)*

    Size AWG or kcmilTemperature Rating of Conductor [See Table 310.104(A).]
    Size AWG or kcmil150°C (302°F)200°C (392°F)250°C (482°F)150°C (302°F)
    Type ZTypes FEP, FEPB, PFA, SA
    Types PFAH, TFE
    Type Z
    COPPERNICKEL OR NICKEL-COATED COPPERALUMINUM OR COPPER-CLAD ALUMINUM1412108344355763645608339547393— 304457141210864321961201431601861101251521711971171481661912157594109124145643211/02/03/04/02152512883322292602973462442733083611691982272601/02/03/04/0*Refer to 310.15(B)(2) for the ampacity correction factors where the ambient temperature is other than 40°C (104°F). Refer to 310.15(B)(3)(a) for more than three current-carrying conductors.
    Table 310.15(B)(19) (formerly Table 310.19) Allowable Ampacities of Single-Insulated Conductors, Rated Up to and Including 2000 Volts, 150°C Through 250°C (302°F Through 482°F), in Free Air, Based on Ambient Air Temperature of 40°C (104°F)*

    Size AWG or kcmilTemperature Rating of Conductor [See Table 310.104(A).]
    Size AWG or kcmil150°C (302°F)200°C (392°F)250°C (482°F)150°C (302°F)
    Type ZTypes FEP, FEPB, PFA, SA
    Types PFAH, TFE
    Type Z
    COPPER
    NICKEL, OR NICKEL- COATED COPPERALUMINUM OR COPPER-CLAD ALUMINUM14121084660801065468901245978107142— 476383141210864321155190214255293165220252293344205278327381440112148170198228643211/02/03/04/03393904515293994675466295325917088302633053514111/02/03/04/0*Refer to 310.15(B)(2) for the ampacity correction factors where the ambient temperature is other than 40°C (104°F).
    Table 310.15(B)(20) (formerly Table 310.20) Ampacities of Not More Than Three Single Insulated Conductors, Rated Up to and Including 2000 Volts, Supported on a Messenger, Based on Ambient Air Temperature of 40°C (104°F)*

    Size AWG or kcmilTemperature Rating of Conductor [See Table 310.104(A).]
    Size AWG or kcmil75°C (167°F)90°C (194°F)75°C (167°F)90°C (194°F)
    Types RHW, THHW, THW, THWN, XHHW, ZWTypes MI, THHN, THHW, THW-2, THWN-2, RHH, RHW-2, USE-2, XHHW, XHHW-2, ZW-2
    Types RHW, THW, THWN, THHW, XHHW
    Types THHN, THHW, RHH, XHHW, RHW-2, XHHW-2, THW-2, THWN-2, USE-2, ZW-2COPPERALUMINUM OR COPPER-CLAD ALUMINUM86432157761011181351586689117138158185445978921061235169911071231448643211/02/03/04/01832122452872142472873351431651922241671932242621/02/03/04/025030035040050032035939743049637441946450358025128231233939229232836439545825030035040050060070075080090010005536106386607047486477147477738268794404885125325726125145705986226697166007007508009001000*Refer to 310.15(B)(2) for the ampacity correction factors where the ambient temperature is other than 40°C (104°F). Refer to 310.15(B)(3)(a) for more than three current-carrying conductors.
  3. Tables. Ampacities for conductors rated 2001 to 35,000 volts shall be as specified in Table 310.60(C)(67) through Table 310.60(C)(86). Ampacities for ambient temper‐ atures other than those specified in the ampacity tables shall be corrected in accordance with 310.60(C)(4).

Informational Note No. 1: For ampacities calculated in accord‐ ance with 310.60(A), reference IEEE 835-1994, Standard Power Cable Ampacity Tables, and the references therein for availability of all factors and constants.

Informational Note No. 2: Ampacities provided by this section do not take voltage drop into consideration. See 210.19(A), Informational Note No. 4, for branch circuits and 215.2(A), Informational Note No. 2, for feeders.

  1. Grounded Shields. Ampacities shown in Table 310.60(C)(69), Table 310.60(C)(70), Table 310.60(C)(81), and Table 310.60(C)(82) shall apply for cables with shields groun‐ ded at one point only. Where shields for these cables are grounded at more than one point, ampacities shall be adjusted to take into consideration the heating due to shield currents.Informational Note: Tables other than those listed contain the ampacity of cables with shields grounded at multiple points.
  2. Burial Depth of Underground Circuits. Where the burial depth of direct burial or electrical duct bank circuits is modi‐ fied from the values shown in a figure or table, ampacities shall be permitted to be modified as indicated in (B)(2)(a) and (B)(2)(b).
    1. Where burial depths are increased in part(s) of an electrical duct run, a decrease in ampacity of the conductors shall not be required, provided the total length of parts of the duct run increased in depth is less than 25 percent of the total run length.
    2. Where burial depths are deeper than shown in a specific underground ampacity table or figure, an ampacity derating factor of 6 percent per 300 mm (1 ft) increase in depth for all values of rho shall be permitted.No ampacity adjustments shall be required where the burial depth is decreased.
  3. Electrical Ducts in Figure 310.60(C)(3). At locations where electrical ducts enter equipment enclosures from under‐ ground, spacing between such ducts, as shown in Figure 310.60(C)(3), shall be permitted to be reduced without requir‐ ing the ampacity of conductors therein to be reduced.
    Table 310.15(B)(21) (formerly Table 310.21) Ampacities of Bare or Covered Conductors in Free Air, Based on 40°C (104°F) Ambient, 80°C (176°F) Total Conductor Temperature, 610 mm/sec (2 ft/sec) Wind Velocity
    imageCopper Conductors AAC Aluminum Conductorsimageimage Bare Covered Bare Covered
    imageAWG or
    imageAWG or
    imageAWG or
    imageAWG orkcmilAmpereskcmilAmpereskcmilAmpereskcmil Amperes89881038768 80612461306966 1014155416341214 1272209221921632 1711/02821/02971/02201/02312/03292/03442/02552/02683/03823/04013/02973/03124/04444/04664/03464/0364250494250519266.8403266.8423300556300584336.4468336.4492500773500812397.5522397.554875010007501050477.0588477.06171000119310001253556.5650556.5682————636.0709636.0744————795.0819795.0860————954.0920——————1033.59681033.51017————12721103 1272 1201————15901267 1590 1381————20001454 2000 1527
  4. Ambient Temperature Correction. Ampacities for ambient temperatures other than those specified in the ampacity tables shall be corrected in accordance with Table 310.60(C)(4) or shall be permitted to be calculated using the following equa‐ tion:

[310.60(C)(4)]

image

T T 

c a

T T

c a

I   I

where:

I′ = ampacity corrected for ambient temperature

I = ampacity shown in the table for Tc and Ta Tc = temperature rating of conductor (°C)

Ta′ = new ambient temperature (°C)

Ta = ambient temperature used in the table (°C)

•

Part III. Construction Specifications

310.104 Conductor Constructions and Applications. Insulated conductors shall comply with the applicable provisions of Table 310.104(A) through Table 310.104(E).

Informational Note: Thermoplastic insulation may stiffen at temperatures lower than −10°C (+14°F). Thermoplastic insula‐ tion may also be deformed at normal temperatures where subjected to pressure, such as at points of support.

image

190 mm

(7.5 in.)

Detail 1

290 mm  290 mm

(11.5 in.  11.5 in.)

Electrical duct bank One electrical duct

image

190 mm (7.5 in.)

190 mm (7.5 in.)

Detail 2

475 mm  475 mm

(19 in.  19 in.) Electrical duct bank Three electrical ducts

or

image

190 mm 190 mm

image

190 mm

(7.5 in.)

190 mm (7.5 in.)

Detail 3

475 mm  675 mm

(19 in.  27 in.) Electrical duct bank Six electrical ducts

190 mm (7.5 in.)

or

image
image

(7.5 in.) (7.5 in.)

675 mm  290 mm

(27 in.  11.5 in.) Electrical duct bank Three electrical ducts

190 mm

(7.5 in.)

190 mm

(7.5 in.)

675 mm  475 mm

(27 in.  19 in.) Electrical duct bank Six electrical ducts

image
image
image

           600 mm          (24 in.)

image
image

            600 mm         (24 in.)

image

Detail 5

Buried 3 conductor cable

190 mm

190 mm

Detail 6

Buried 3 conductor cables

Detail 7

Buried triplexed cables (1 circuit)

190 mm 190 mm

Detail 8

Buried triplexed cables (2 circuits)

190 mm 190 mm

image

(24 in.)

image

(7.5 in.)

(7.5 in.)

(7.5 in.)

(7.5 in.)

600 mm

(7.5 in.)

(7.5 in.)

Detail 9

Buried single-conductor cables (1 circuit)

Detail 10

Buried single-conductor cables (2 circuits)

Note: Minimum burial depths to top electrical ducts or cables shall be

in accordance with 300.50. Maximum depth to the top of electrical duct banks shall be 750 mm (30 in.) and maximum depth to the top of direct-buried cables shall be 900 mm (36 in.).

Legend

image Backfill (earth or concrete) image Electrical duct

image

Cable or cables

FIGURE 310.60(C)(3) Cable Installation Dimensions for Use with Table 310.60(C)(77) Through Table 310.60(C)(86).

Table 310.60(C)(4) Ambient Temperature Correction Factors

image

For ambient temperatures other than 40°C (104°F), multiply the allowable ampacities specified in the ampacity tables by the

Table 310.60(C)(68) Ampacities of Insulated Single Aluminum Conductor Cables Triplexed in Air Based on Conductor Temperatures of 90°C (194°F) and 105°C (221°F) and Ambient Air Temperature of 40°C (104°F)*

appropriate factor shown below.                                                                                                                                       

image
Ambient Temperature (°C)Temperature Rating of ConductorAmbient Temperature (°F)
90°C105°C
10 or less1.261.2150 or less
11–151.221.1851–59
16–201.181.1460–68
21–251.141.1169–77
26–301.101.0778–86
31–351.051.0487–95
36–401.001.0096–104
41–450.950.96105–113
46–500.890.92114–122
51–550.840.88123–131
56–600.770.83132–140
61–650.710.78141–149
66–700.630.73150–158
71–750.550.68159–167
76–800.450.62168–176
81–850.320.55177–185
86–90—0.48186–194
91–95—0.39195–203
96–100—0.28204–212

Temperature Rating of Conductor [See Table 310.104(C).]

Conductor

2001–5000 Volts

image

Ampacity

105°C

5001–35,000 Volts

Ampacity

105°C

Size (AWG

or kcmil)

90°C (194°F)

Type MV-90

(221°F)

Type MV-105

90°C (194°F)

Type MV-90

(221°F)

Type MV-105

85057——
670777584
490100100110
2125135130150
1145160150175
1/0170185175200
2/0195215200230
3/0225250230265
4/0265290270305
250295325300335
350365405370415
500460510460515
750600665590660
1000715800700780

Table 310.60(C)(67) Ampacities of Insulated Single Copper Conductor Cables Triplexed in Air Based on Conductor Temperatures of 90°C (194°F) and 105°C (221°F) and Ambient Air Temperature of 40°C (104°F)*

image
image

Temperature Rating of Conductor [See Table 310.104(C).]

*Refer to 310.60(C)(4) for the ampacity correction factors where the ambient air temperature is other than 40°C (104°F).

2001–5000 Volts

Ampacity

5001–35,000 Volts

Ampacity

Conductor Size (AWGor kcmil)
90°C (194°F)Type MV-90		105°C (221°F)Type MV-105
90°C (194°F)Type MV-90		105°C (221°F)Type MV-105
86574——
69099100110
4120130130140
2160175170195
1185205195225
1/0215240225255
2/0250275260295
3/0290320300340
4/0335375345390
250375415380430
350465515470525
500580645580650
750750835730820
1000880980850950

*Refer to 310.60(C)(4) for the ampacity correction factors where the ambient air temperature is other than 40°C (104°F).

Table 310.60(C)(69) Ampacities of Insulated Single Copper Conductor Isolated in Air Based on Conductor Temperatures of 90°C (194°F) and 105°C (221°F) and Ambient Air Temperature of 40°C (104°F)*

image
image

Temperature Rating of Conductor [See Table 310.104(C).]

Table 310.60(C)(70) Ampacities of Insulated Single Aluminum Conductor Isolated in Air Based on Conductor Temperatures of 90°C (194°F) and 105°C (221°F) and Ambient Air Temperature of 40°C (104°F)*

image
image

Temperature Rating of Conductor [See Table 310.104(C).]

2001–5000 Volts

image

Ampacity

5001–

15,000 Volts Ampacity

15,001–

35,000 Volts Ampacity

2001–5000 Volts

image

Ampacity

5001–

15,000 Volts Ampacity

15,001–

35,000 Volts Ampacity

Conductor

90°C

105°C

90°C

105°C

90°C

105°C

Conductor

90°C

105°C

90°C

105°C

90°C

105°C

Size

(194°F) (221°F)

(194°F)

(221°F)

(194°F)

(221°F)

Size

(194°F) (221°F)

(194°F)

(221°F)

(194°F)

(221°F)

(AWG

Type

Type

Type

Type

Type

Type

(AWG

Type

Type

Type

Type

Type

Type

or kcmil)MV-90MV-105MV-90MV-105MV-90MV-105or kcmil)MV-90MV-105MV-90MV-105MV-90MV-105
88393————86471————
6110120110125——685958797——
4145160150165——4115125115130——
2190215195215——2150165150170——
12252502252502252501175195175195175195
1/02602902602902602901/0200225200225200225
2/03003303003353003302/0230260235260230260
3/03453853453853453803/0270300270300270300
4/04004454004453954454/0310350310350310345
250445495445495440490250345385345385345380
350550615550610545605350430480430480430475
500695775685765680755500545605535600530590
7509001000885990870970750710790700780685765
10001075120010601185104011601000855950840940825920
12501230137012101350118513201250980109597010809501055
15001365152513451500131514651500110512301085121510601180
17501495166514701640143015951750121513551195133511651300
20001605179015751755153517102000132014751295144512651410

*Refer to 310.60(C)(4) for the ampacity correction factors where the ambient air temperature is other than 40°C (104°F).

*Refer to 310.60(C)(4) for the ampacity correction factors where the ambient air temperature is other than 40°C (104°F).

Table 310.60(C)(71) Ampacities of an Insulated Three- Conductor Copper Cable Isolated in Air Based on Conductor Temperatures of 90°C (194°F) and 105°C (221°F) and Ambient Air Temperature of 40°C (104°F)*

image
image

Temperature Rating of Conductor [See Table 310.104(C).]

Table 310.60(C)(72) Ampacities of an Insulated Three- Conductor Aluminum Cable Isolated in Air Based on Conductor Temperatures of 90°C (194°F) and 105°C (221°F) and Ambient Air Temperature of 40°C (104°F)*

image
image

Temperature Rating of Conductor [See Table 310.104(C).]

2001–5000 Volts

Ampacity

5001–35,000 Volts

Ampacity

2001–5000 Volts

Ampacity

5001–35,000 Volts

Ampacity

Conductor Size (AWGor kcmil)90°C (194°F)Type MV-90105°C (221°F)Type MV-10590°C (194°F)Type MV-90105°C (221°F)Type MV-105Conductor Size (AWGor kcmil)90°C (194°F)Type MV-90105°C (221°F)Type MV-10590°C (194°F)Type MV-90105°C (221°F)Type MV-105
85966——84651——
6798893105661687280
41051151201354819095105
21401541651852110120125145
11601801852101125140145165
1/01852052152401/0145160170185
2/02152402452752/0170185190215
3/0250280285315
4/0285320325360
250320355360400
350395440435490
500485545535600
750615685670745
1000705790770860

*Refer to 310.60(C)(4) for the ampacity correction factors where the ambient air temperature is other than 40°C (104°F).

3/0195215220245
4/0225250255285
250250280280315
350310345345385
500385430425475
750495550540600
1000585650635705

*Refer to 310.60(C)(4) for the ampacity correction factors where the ambient air temperature is other than 40°C (104°F).

Table 310.60(C)(73) Ampacities of an Insulated Triplexed or Three Single-Conductor Copper Cables in Isolated Conduit in Air Based on Conductor Temperatures of 90°C (194°F) and 105°C (221°F) and Ambient Air Temperature of 40°C (104°F)*

image
image

Temperature Rating of Conductor [See Table 310.104(C).]

Table 310.60(C)(74) Ampacities of an Insulated Triplexed or Three Single-Conductor Aluminum Cables in Isolated Conduit in Air Based on Conductor Temperatures of 90°C (194°F) and 105°C (221°F) and Ambient Air Temperature of 40°C (104°F)*

image
image

Temperature Rating of Conductor [See Table 310.104(C).]

2001–5000 Volts

Ampacity

5001–35,000 Volts

Ampacity

2001–5000 Volts

Ampacity

5001–35,000 Volts

Ampacity

Conductor Size (AWGor kcmil)90°C (194°F)Type MV-90105°C (221°F)Type MV-10590°C (194°F)Type MV-90105°C (221°F)Type MV-105
Conductor Size (AWG or kcmil)		90°C (194°F)Type MV-90105°C (221°F)Type MV-10590°C (194°F)Type MV-90105°C (221°F)Type MV-105
85561——84348——
675848393658656572
497110110120476858494
21301451501652100115115130
11551751701901120135130150
1/01802001952151/0140155150170
2/02052252252552/0160175175200
3/02402702602903/0190210200225
4/02803052953304/0215240230260
250315355330365250250280255290
350385430395440350305340310350
500475530480535500380425385430
750600665585655750490545485540
10006907706757551000580645565640

*Refer to 310.60(C)(4) for the ampacity correction factors where the ambient air temperature is other than 40°C (104°F).

*Refer to 310.60(C)(4) for the ampacity correction factors where the ambient air temperature is other than 40°C (104°F).

Table 310.60(C)(75) Ampacities of an Insulated Three- Conductor Copper Cable in Isolated Conduit in Air Based on Conductor Temperatures of 90°C (194°F) and 105°C (221°F) and Ambient Air Temperature of 40°C (104°F)*

image
image

Temperature Rating of Conductor [See Table 310.104(C).]

Table 310.60(C)(76) Ampacities of an Insulated Three- Conductor Aluminum Cable in Isolated Conduit in Air Based on Conductor Temperatures of 90°C (194°F) and 105°C (221°F) and Ambient Air Temperature of 40°C (104°F)*

image
image

Temperature Rating of Conductor [See Table 310.104(C).]

2001–5000 Volts

Ampacity

5001–35,000 Volts

Ampacity

2001–5000 Volts

Ampacity

5001–35,000 Volts

Ampacity

Conductor Size (AWGor kcmil)90°C (194°F)Type MV-90105°C (221°F)Type MV-10590°C (194°F)Type MV-90105°C (221°F)Type MV-105Conductor Size (AWGor kcmil)90°C (194°F)Type MV-90105°C (221°F)Type MV-10590°C (194°F)Type MV-90105°C (221°F)Type MV-105
85258——84146——
669778392653596471
491100105120471798494
2125135145165296105115125
11401551651851110125130145
1/01651851952151/0130145150170
2/01902102202452/0150165170190
3/02202452502803/0170190195220
4/02552852903204/0200225225255
250280315315350250220245250280
350350390385430350275305305340
500425475470525500340380380425
750525585570635750430480470520
10005906606507251000505560550615

*Refer to 310.60(C)(4) for the ampacity correction factors where the ambient air temperature is other than 40°C (104°F).

*Refer to 310.60(C)(4) for the ampacity correction factors where the ambient air temperature is other than 40°C (104°F).

Table 310.60(C)(77) Ampacities of Three Single-Insulated Copper Conductors in Underground Electrical Ducts (Three Conductors per Electrical Duct) Based on Ambient Earth Temperature of 20°C (68°F), Electrical Duct Arrangement in Accordance with Figure 310.60(C)(3), 100 Percent Load Factor, Thermal Resistance (RHO) of 90, Conductor Temperatures of 90°C (194°F) and 105°C (221°F)

image
image

Temperature Rating of Conductor [See Table 310.104(C).]

Table 310.60(C)(78) Ampacities of Three Single-Insulated Aluminum Conductors in Underground Electrical Ducts (Three Conductors per Electrical Duct) Based on Ambient Earth Temperature of 20°C (68°F), Electrical Duct Arrangement in Accordance with Figure 310.60(C)(3), 100 Percent Load Factor, Thermal Resistance (RHO) of 90, Conductor Temperatures of 90°C (194°F) and 105°C (221°F)

image
image

Temperature Rating of Conductor [See Table 310.104(C).]

2001–5000 Volts

Ampacity

5001–35,000 Volts

Ampacity

2001–5000 Volts

Ampacity

5001–35,000 Volts

Ampacity

90°C105°C90°C105°C90°C105°C90°C105°C
Conductor Size(194°F)(221°F)(194°F)(221°F)Conductor Size(194°F)(221°F)(194°F)(221°F)
(AWGTypeTypeTypeType(AWGTypeTypeTypeType
or kcmil)MV-90MV-105MV-90MV-105or kcmil)MV-90MV-105MV-90MV-105
One Circuit [See FigureOne Circuit [See Figure
310.60(C)(3), Detail 1.]310.60(C)(3), Detail 1.]
86469——85054——
685929097666717075
4110120115125486939198
21451551551652115125120130
11701801751851130140135145
1/01952102002151/0150160155165
2/02202352302452/0170185175190
3/02502702602753/0195210200215
4/02903102953154/0225245230245
250320345325345250250270250270
350385415390415350305325305330
500470505465500500370400370400
750585630565610750470505455490
10006707206406901000545590525565
Three Circuits [See FigureThree Circuits [See Figure
310.60(C)(3), Detail 2.]310.60(C)(3), Detail 2.]
85660——84447——
673797783657616065
49510099105474807783
2125130130135296105100105
11401501451551110120110120
1/01601751651751/0125135125140
2/01851951852002/0145155145155
3/02102252102253/0160175165175
4/02352552402554/0185200185200
250260280260280250205220200220
350315335310330350245265245260
500375405370395500295320290315
750460495440475750370395355385
10005255654955351000425460405440
Six Circuits [See FigureSix Circuits [See Figure
310.60(C)(3), Detail 3.]310.60(C)(3), Detail 3.]
84852——83841——
662676468648525054
480868288462676469
2105110105115280868088
1115125120125191989099
1/01351451351451/0105110105110
2/01501601501652/0115125115125
3/01701851701853/0135145130145
4/01952101902054/0150165150160
250210225210225250165180165175
350250270245265350195210195210
500300325290310500240255230250
750365395350375750290315280305
10004104453904151000335360320345

Table 310.60(C)(79) Ampacities of Three Insulated Copper Conductors Cabled Within an Overall Covering (Three- Conductor Cable) in Underground Electrical Ducts (One Cable per Electrical Duct) Based on Ambient Earth Temperature of 20°C (68°F), Electrical Duct Arrangement in Accordance with Figure 310.60(C)(3), 100 Percent Load Factor, Thermal Resistance (RHO) of 90, Conductor Temperatures of 90°C (194°F) and 105°C (221°C)

image
image

Temperature Rating of Conductor [See Table 310.104(C).]

Table 310.60(C)(80) Ampacities of Three Insulated Aluminum Conductors Cabled Within an Overall Covering (Three- Conductor Cable) in Underground Electrical Ducts (One Cable per Electrical Duct) Based on Ambient Earth Temperature of 20°C (68°F), Electrical Duct Arrangement in Accordance with Figure 310.60(C)(3), 100 Percent Load Factor, Thermal Resistance (RHO) of 90, Conductor Temperatures of 90°C (194°F) and 105°C (221°C)

image
image

Temperature Rating of Conductor [See Table 310.104(C).]

2001–5000 Volts

Ampacity

5001–35,000 Volts

Ampacity

2001–5000 Volts

Ampacity

5001–35,000 Volts

Ampacity


Conductor Size (AWGor kcmil)		90°C (194°F)Type MV-90105°C (221°F)Type MV-10590°C (194°F)Type MV-90105°C (221°F)Type MV-105
Conductor Size (AWGor kcmil)		90°C (194°F)Type MV-90105°C (221°F)Type MV-10590°C (194°F)Type MV-90105°C (221°F)Type MV-105
One Circuit [See FigureOne Circuit [See Figure
310.60(C)(3), Detail 1.]310.60(C)(3), Detail 1.]
85964——84650——
678848895661666974
4100110115125480868996
21351451501602105110115125
11551651701851120130135145
1/01751901952101/0140150150165
2/02002202202352/0160170170185
3/02302502502703/0180195195210
4/02652852853054/0205220220240
250290315310335250230245245265
350355380375400350280310295315
500430460450485500340365355385
750530570545585750425460440475
10006006456156601000495535510545
Three Circuits [See FigureThree Circuits [See Figure
310.60(C)(3), Detail 2.]310.60(C)(3), Detail 2.]
85357——84144——
669747581654585964
4899697105470757581
211512512513529097100105
11351451401551105110110120
1/01501651601751/0120125125135
2/01701851851952/0135145140155
3/01952102052203/0155165160175
4/02252402302504/0175185180195
250245265255270250190205200215
350295315305325350230250240255
500355380360385500280300285305
750430465430465750345375350375
10004855204855151000400430400430
Six Circuits [See FigureSix Circuits [See Figure
310.60(C)(3), Detail 3.]310.60(C)(3), Detail 3.]
84650——83639——
660656368646504953
477838187460656368
298105105110277838086
1110120115125187949098
1/01251351301451/099105105110
2/01451551501602/0110120115125
3/01651751701803/0130140130140
4/01852001902004/0145155150160
250200220205220250160170160170
350240270245275350190205190205
500290310290305500230245230245
750350375340365750280305275295
10003904203804051000320345315335

Table 310.60(C)(81) Ampacities of Single Insulated Copper Conductors Directly Buried in Earth Based on Ambient Earth Temperature of 20°C (68°F), Arrangement per Figure 310.60(C)(3), 100 Percent Load Factor, Thermal Resistance (RHO) of 90, Conductor Temperatures of 90°C (194°F) and 105°C (221°C)

image
image

Temperature Rating of Conductor [See Table 310.104(C).]

Table 310.60(C)(82) Ampacities of Single Insulated Aluminum Conductors Directly Buried in Earth Based on Ambient Earth Temperature of 20°C (68°F), Arrangement per Figure 310.60(C)(3), 100 Percent Load Factor, Thermal Resistance (RHO) of 90, Conductor Temperatures of 90°C (194°F) and 105°C (221°F)

image
image

Temperature Rating of Conductor [See Table 310.104(C).]

2001–5000 Volts

Ampacity

5001–35,000 Volts

Ampacity

2001–5000 Volts

Ampacity

5001–35,000 Volts

Ampacity

90°C105°C90°C105°C90°C105°C90°C105°C
Conductor Size(194°F)(221°F)(194°F)(221°F)Conductor Size(194°F)(221°F)(194°F)(221°F)
(AWGTypeTypeTypeType(AWGTypeTypeTypeType
or kcmil)MV-90MV-105MV-90MV-105or kcmil)MV-90MV-105MV-90MV-105
image

One Circuit, Three Conductors [See Figure 310.60(C)(3), Detail 9.]

image

One Circuit, Three Conductors [See Figure 310.60(C)(3), Detail 9.]

8110115——88590——
61401501301406110115100110
41801951701804140150130140
22302502102252180195165175
12602802402601205220185200
1/02953202752951/0230250215230
2/03353653103352/0265285245260
3/03854153553803/0300320275295
4/04354654054354/0340365315340
250470510440475250370395345370
350570615535575350445480415450
500690745650700500540580510545
750845910805865750665720635680
1000980105593010051000780840740795
Two Circuits, SixTwo Circuits, Six
Conductors [See Figure Conductors [See Figure310.60(C)(3), Detail 10.] 310.60(C)(3), Detail 10.]
8100110——88085——
6130140120130610011095100
41651801601704130140125130
22152301952102165180155165
12402602252401190200175190
1/02752952552751/0215230200215
2/03103352903152/0245260225245
3/03553803303553/0275295255275
4/04004303754054/0310335290315
250435470410440250340365320345
350520560495530350410440385415
500630680600645500495530470505
750775835740795750610655580625
10008909608559201000710765680730

Table 310.60(C)(83) Ampacities of Three Insulated Copper Conductors Cabled Within an Overall Covering (Three- Conductor Cable), Directly Buried in Earth Based on Ambient Earth Temperature of 20°C (68°F), Arrangement per Figure 310.60(C)(3), 100 Percent Load Factor, Thermal Resistance (RHO) of 90, Conductor Temperatures of 90°C (194°F) and 105°C (221°F)

image
image

Temperature Rating of Conductor [See Table 310.104(C).]

Table 310.60(C)(84) Ampacities of Three Insulated Aluminum Conductors Cabled Within an Overall Covering (Three- Conductor Cable), Directly Buried in Earth Based on Ambient Earth Temperature of 20°C (68°F), Arrangement per Figure 310.60(C)(3), 100 Percent Load Factor, Thermal Resistance (RHO) of 90, Conductor Temperatures of 90°C (194°F) and 105°C (221°F)

image
image

Temperature Rating of Conductor [See Table 310.104(C).]

2001–5000 Volts

Ampacity

5001–35,000 Volts

Ampacity

2001–5000 Volts

Ampacity

5001–35,000 Volts

Ampacity

90°C105°C90°C105°C90°C105°C90°C105°C
Conductor Size(194°F)(221°F)(194°F)(221°F)Conductor Size(194°F)(221°F)(194°F)(221°F)
(AWGTypeTypeTypeType(AWGTypeTypeTypeType
or kcmil)MV-90MV-105MV-90MV-105or kcmil)MV-90MV-105MV-90MV-105
image

One Circuit [See Figure 310.60(C)(3), Detail 5.]

image

One Circuit [See Figure 310.60(C)(3), Detail 5.]

88589——86570——
6105115115120680889095
41351501451554105115115125
21801901852002140150145155
12002152102251155170165175
1/02302452402551/0180190185200
2/02602802702902/0205220210225
3/02953203053303/0230250240260
4/03353603503754/0260280270295
250365395380410250285310300320
350440475460495350345375360390
500530570550590500420450435470
750650700665720750520560540580
10007307857508101000600650620665

Two Circuits [See Figure 310.60(C)(3), Detail 6.]

Two Circuits [See Figure 310.60(C)(3), Detail 6.]

88084——86066——
6100105105115675838095
41301401351454100110105115
21651801701852130140135145
11852001952101145155150165
1/02152302202351/0165180170185
2/02402602502702/0190205195210
3/02752952803053/0215230220240
4/03103353203454/0245260250270
250340365350375250265285275295
350410440420450350320345330355
500490525500535500385415395425
750595640605650750480515485525
10006657156757301000550590560600

Table 310.60(C)(85) Ampacities of Three Triplexed Single Insulated Copper Conductors Directly Buried in Earth Based on Ambient Earth Temperature of 20°C (68°F), Arrangement per Figure 310.60(C)(3), 100 Percent Load Factor, Thermal Resistance (RHO) of 90, Conductor Temperatures 90°C (194°F) and 105°C (221°F)

image
image

Temperature Rating of Conductor [See Table 310.104(C).]

Table 310.60(C)(86) Ampacities of Three Triplexed Single Insulated Aluminum Conductors Directly Buried in Earth Based on Ambient Earth Temperature of 20°C (68°F), Arrangement per Figure 310.60(C)(3), 100 Percent Load Factor, Thermal Resistance (RHO) of 90, Conductor Temperatures 90°C (194°F) and 105°C (221°F)

image
image

Temperature Rating of Conductor [See Table 310.104(C).]

2001–5000 Volts

Ampacity

5001–35,000 Volts

Ampacity

2001–5000 Volts

Ampacity

5001–35,000 Volts

Ampacity

90°C105°C90°C105°C90°C105°C90°C105°C
Conductor Size(194°F)(221°F)(194°F)(221°F)Conductor Size(194°F)(221°F)(194°F)(221°F)
(AWGTypeTypeTypeType(AWGTypeTypeTypeType
or kcmil)MV-90MV-105MV-90MV-105or kcmil)MV-90MV-105MV-90MV-105
image

One Circuit, Three Conductors [See Figure 310.60(C)(3), Detail 7.]

image

One Circuit, Three Conductors [See Figure 310.60(C)(3), Detail 7.]

89095——87075——
61201301151206901009095
41501651501604120130115125
21952051902052155165145155
12252402152301175190165175
1/02552702452601/0200210190205
2/02903102752952/0225240215230
3/03303603153403/0255275245265
4/03754053603854/0290310280305
250410445390410250320350305325
350490580470505350385420370400
500590635565605500465500445480
750725780685740750580625550590
10008258857708301000670725635680
Two Circuits, SixTwo Circuits, Six
Conductors [See Figure Conductors [See Figure310.60(C)(3), Detail 8.] 310.60(C)(3), Detail 8.]
88590——86570——
6110115105115685958590
41401501401504110120105115
21801951751902140150135145
12052202002151160170155170
1/02352502252401/0180195175190
2/02652852552752/0205220200215
3/03003202903153/0235250225245
4/03403653253504/0265285255275
250370395355380250290310280300
350445480425455350350375335360
500535575510545500420455405435
750650700615660750520560485525
10007407956907451000600645565605

Table 310.104(A) Conductor Applications and Insulations Rated 600 Volts1


Trade Name
Type Letter		Maximum Operating Temperature
Application Provisions
Insulation		Thickness of Insulation
Outer Covering2
AWG or kcmil
mm
mils
Fluorinated ethylene propyleneFEP orFEPB90°C (194°F)
200°C (392°F)		Dry and damp locations
Dry locations — special applications3		Fluorinated ethylene propyleneFluorinated ethylene propylene14–108–20.510.762030None
14–80.3614Glass braid
6–20.3614Glass or other suitable braid material
Mineral insulation (metal sheathed)MI90°C (194°F) 250°C (482°F)Dry and wet locations
For special applications3		Magnesium oxide18–16416–109–43–5000.580.911.271.4023365055Copper or alloy steel
Moisture-, heat-, and oil-resistant thermoplasticMTW60°C (140°F)90°C (194°F)Machine tool wiring in wet locations Machine tool wiring in dry locations.
Informational Note: See NFPA 79.		Flame-retardant, moisture-, heat-, and oil-resistant thermoplastic
22–1210864–21–4/0213–500501–1000		(A)(B)(A)(B)NoneNylon jacket or equivalent
0.760.761.141.521.522.032.412.790.380.510.760.761.021.271.521.78303045606080951101520303040506070
Paper85°C (185°F)For underground service conductors, or by special permissionPaperLead sheath
Perfluoro-alkoxyPFA90°C (194°F)200°C (392°F)Dry and damp locationsPerfluoro-alkoxy14–108–21–4/00.510.761.14203045None
Dry locations — special applications3
Perfluoro-alkoxyPFAH250°C (482°F)Dry locations only. Only for leads within apparatus or within raceways connected to apparatus (nickel or nickel-coated copper only)Perfluoro-alkoxy14–108–21–4/00.510.761.14203045None
ThermosetRHH90°C (194°F)Dry and damp locations14-108–21–4/0213–500501–10001001–20001.141.522.032.412.793.1845608095110125Moisture-resistant, flame- retardant, nonmetallic covering2
Moisture-resistant thermosetRHW75°C (167°F)Dry and wet locationsFlame-retardant, moisture- resistant thermoset14–108–21–4/0213–500501–10001001–20001.141.522.032.412.793.1845608095110125Moisture-resistant, flame- retardant, nonmetallic covering
RHW-290°C (194°F)
SiliconeSA90°C (194°F)
200°C (392°F)		Dry and damp locations
For special application3		Silicone rubber14–108–21–4/0213–500501–10001001–20001.141.522.032.412.793.1845608095110125Glass or other suitable braid material

(continues)

Table 310.104(A) Continued


Trade Name
Type Letter		Maximum Operating Temperature
Application Provisions
Insulation		Thickness of Insulation
Outer Covering2
AWG or kcmil
mm
mils
ThermosetSIS90°C (194°F)Switchboard and switchgear wiring onlyFlame-retardant thermoset14–108–21–4/00.761.142.41304555None
Thermoplastic and fibrous outer braidTBS90°C (194°F)Switchboard and switchgear wiring onlyThermoplastic14–1086–21–4/00.761.141.522.0330456080Flame-retardant, nonmetallic covering
Extended polytetra- fluoro-ethyleneTFE250°C (482°F)Dry locations only. Only for leads within apparatus or within raceways connected to apparatus, or as open wiring (nickel or nickel-coated copper only)Extruded polytetra- fluoroethylene14–108–21–4/00.510.761.14203045None
Heat-resistant thermoplasticTHHN90°C (194°F)Dry and damp locationsFlame-retardant, heat-resistant thermoplastic14–12108–64–21–4/0250–500501–10000.380.510.761.021.271.521.7815203040506070Nylon jacket or equivalent
Moisture- and heat- resistant thermoplasticTHHW75°C (167°F)
90°C (194°F)		Wet location Dry locationFlame-retardant, moisture- and heat-resistant thermoplastic14–1086–21–4/0213–500501–10001001–20000.761.141.522.032.412.793.183045608095110125None
Moisture- and heat- resistant thermoplasticTHW75°C (167°F)90°C (194°F)Dry and wet locations
Special applications within electric discharge lighting equipment.Limited to 1000 open-circuit volts or less. (Size 14-8only as permitted in 410.68.)		Flame-retardant, moisture- and heat-resistant thermoplastic14–1086–21–4/0213–500501–10001001–20000.761.141.522.032.412.793.183045608095110125None
THW-290°C(194°F)Dry and wet locations
Moisture- and heat- resistant thermoplasticTHWN75°C (167°F)Dry and wet locationsFlame-retardant, moisture- and heat-resistant thermoplastic14–12108–64–21–4/0250–500501–10000.380.510.761.021.271.521.7815203040506070Nylon jacket or equivalent
THWN-290°C (194°F)
Moisture-resistant thermoplasticTW60°C (140°F)Dry and wet locationsFlame-retardant, moisture- resistant thermoplastic14–1086–21–4/0213–500501–10001001–20000.761.141.522.032.412.793.18345608095110125None
Underground feeder and branch-circuit cable — single conductor (for Type UF cable employing more than one conductor, see Article 340).UF60°C (140°F)75°C (167°F) 5See Article 340.Moisture-resistant
Moisture- and heat- resistant		14–108–21–4/01.522.032.41606806956Integral with insulation

(continues)

Table 310.104(A) Continued


Trade Name
Type Letter		Maximum Operating Temperature
Application Provisions
Insulation		Thickness of Insulation
Outer Covering2
AWG or kcmil
mm
mils
Underground service- entrance cable — single conductor (for Type USE cable employing more than one conductor, see Article 338).USE75°C (167°F) 5See Article 338.Heat- and moisture- resistant14–108–21–4/0213–500501–10001001–20001.141.522.032.412.793.1845608095 7110125Moisture-resistant nonmetallic covering (See 338.2.)
USE-290°C(194°F)Dry and wet locations
ThermosetXHH90°C (194°F)Dry and damp locationsFlame-retardant thermoset14–108–21–4/0213–500501–10001001–20000.761.141.401.652.032.41304555658095None
ThermosetXHHN90°C (194°F)Dry and damp locationsFlame-retardant thermoset14–12 0.3815203040506070Nylon jacket or equivalent
108–64–21–4/0250–500501–10000.510.761.021.271.521.78
Moisture-resistant thermosetXHHW90°C (194°F)75°C (167°F)Dry and damp locationsFlame-retardant, moisture- resistant thermoset14–108–21–4/0213–500501–10001001–20000.761.141.401.652.032.41304555658095None
Wet locations
Moisture-resistant thermosetXHHW-290°C (194°F)Dry and wet locationsFlame-retardant, moisture- resistant thermoset14–108–21–4/0213–500501–10001001–20000.761.141.401.652.032.41304555658095None
Moisture-resistant thermosetXHWN75°C (167°F)Dry and wet locationsFlame-retardant, moisture- resistant thermoset14–12108–64–21–4/0250–500501–10000.380.510.761.021.271.521.7815203040506070Nylon jacket or equivalent
XHWN-290°C(194°F)
Modified ethylene tetrafluoro-ethyleneZ90°C (194°F)Dry and damp locationsModified ethylene tetrafluoro- ethylene14–12108–43–11/0–4/00.380.510.640.891.141520253545None
150°C (302°F)Dry locations — special applications3
Modified ethylene tetrafluoro-ethyleneZW75°C (167°F)90°C (194°F) 150°C (302°F)Wet locationsModified ethylene tetrafluoro- ethylene14–108–20.761.143045None
Dry and damplocationsDry locations — special applications3
ZW-290°C (194°F)Dry and wet locations

1Conductors can be rated up to 1000 V if listed and marked.

2 Some insulations do not require an outer covering.

3 Where design conditions require maximum conductor operating temperatures above 90°C (194°F).

4 For signaling circuits permitting 300-volt insulation.

5 For ampacity limitation, see 340.80.

6 Includes integral jacket.

7 Insulation thickness shall be permitted to be 2.03 mm (80 mils) for listed Type USE conductors that have been subjected to special investigations. The nonmetallic covering over individual rubber-covered conductors of aluminum-sheathed cable and of lead-sheathed or multiconductor cable shall not be required to be flame retardant. For Type MC cable, see 330.104. For nonmetallic-sheathed cable, see Article 334, Part III. For Type UF cable, see Article 340, Part III.

Table 310.104(B) Thickness of Insulation for Nonshielded Types RHH and RHW Solid Dielectric Insulated Conductors Rated 2000 Volts

image
(AWG or kcmil)mmmilsmmmils
14–102.03801.5260
82.03801.7870
6–22.41951.7870
1–2/02.791102.2990
3/0–4/02.791102.2990
213–5003.181252.67105
501–10003.561403.05120
1001–20003.561403.56140

Conductor Size

Column A1 Column B2

1Column A insulations are limited to natural, SBR, and butyl rubbers.

2Column B insulations are materials such as cross-linked polyethylene, ethylene propylene rubber, and compo‐ sites thereof.

Table 310.104(C) Conductor Application and Insulation Rated 2001 Volts and Higher

Trade Name
Type Letter		Maximum Operating TemperatureApplication Provision
Insulation
Outer Covering
Medium voltage solidMV-9090°CDry or wetThermoplastic orJacket, sheath, or
dielectricMV-105*105°Clocationsthermosettingarmor

*Where design conditions require maximum conductor temperatures above 90°C.

Table 310.104(D) Thickness of Insulation and Jacket for Nonshielded Solid Dielectric Insulated Conductors Rated 2001 to 5000 Volts

image
image

Dry Locations, Single Conductor Wet or Dry Locations

Without Jacket

image
image
image

With Jacket Single Conductor Multiconductor

(AWG or kcmil)mmmilsmmmilsmmmilsmmmilsmmmilsmmmils
82.791102.29900.76303.181252.03802.2990
62.791102.29900.76303.181252.03802.2990
4–22.791102.29901.14453.181252.03802.2990
1–2/02.791102.29901.14453.181252.03802.2990
3/0–4/02.791102.29901.65653.181252.41952.2990
213–5003.051202.29901.65653.561402.791102.2990
501–7503.301302.29901.65653.941553.181252.2990
751–10003.301302.29901.65653.941553.181252.2990
1001–12503.561402.921151.65654.321703.561402.92115
1251–15003.561402.921152.03804.321703.561402.92115
1501–20003.561402.921152.03804.321703.941553.56140

Conductor Size

Insulation

Insulation Jacket Insulation Jacket

Insulation*

*Under a common overall covering such as a jacket, sheath, or armor.

Table 310.104(E) Thickness of Insulation for Shielded Solid Dielectric Insulated Conductors Rated 2001 to 35,000 Volts

image

2001–5000

image

Volts 5001–8000 Volts 8001–15,000 Volts 15,001–25,000 Volts

Conductor Size

100 Percent Insulation

Level 1

100 Percent Insulation

Level 1

133 Percent Insulation

Level 2

173

Percent Insulation

Level3

100 Percent Insulation

Level1

133 Percent Insulation

Level2

173

Percent Insulation

Level3

100 Percent Insulation

Level1

133 Percent Insulation

Level2

173

Percent Insulation

Level 3

(AWG                                                                                                                                                                                                                                                                                                                                                     

or kcmil) mm mils mm mils mm mils mm mils mm mils mm mils mm mils mm mils mm mils mm mils

image

8 2.29 90 — — — — — — — — — — — — — — — — — —

6–4 2.29 90 2.92 115 3.56 140 4.45 175 — — — — — — — — — — — —

2 2.29 90 2.92 115 3.56 140 4.45 175 4.45 175 5.59 220 6.60 260 — — — — — —

1 2.29 90 2.92 115 3.56 140 4.45 175 4.45 175 5.59 220 6.60 260 6.60 260 8.13 320 10.67 420

1/0–2000 2.29 90 2.92 115 3.56 140 4.45 175 4.45 175 5.59 220 6.60 260 6.60 260 8.13 320 10.67 420

image
image

25,001–28,000 Volts 28,001–35,000 Volts

Conductor Size

100 Percent Insulation

Level1

133 Percent Insulation

Level 2

173

Percent

Insulation Level3

100 Percent Insulation

Level1

133 Percent Insulation

Level2

173

Percent

Insulation Level3

(AWG                                                                                                                                                                                                                                                                                                                  

or kcmil) mm mils mm mils mm mils mm mils mm mils mm mils

17.112808.7634511.30445——————
1/0–20007.112808.7634511.304458.7634510.6742014.73580

1 100 Percent Insulation Level. Cables in this category shall be permitted to be applied where the system is provided with relay protection such that ground faults will be cleared as rapidly as possible but, in any case, within 1 minute. While these cables are applicable to the great majority of cable installations that are on grounded systems, they shall be permitted to be used also on other systems for which the application of cables is acceptable, provided the above clearing requirements are met in completely de-energizing the faulted section.

2 133 Percent Insulation Level. This insulation level corresponds to that formerly designated for ungrounded systems. Cables in this category shall be permitted to be applied in situations where the clearing time requirements of the 100 percent level category cannot be met and yet there is adequate assurance that the faulted section will be de-energized in a time not exceeding 1 hour. Also, they shall be permitted to be used in 100 percent insula‐ tion level applications where additional insulation is desirable.

3 173 Percent Insulation Level. Cables in this category shall be permitted to be applied under all of the following conditions:

  1. In industrial establishments where the conditions of maintenance and supervision ensure that only qualified persons service the installation
  2. Where the fault clearing time requirements of the 133 percent level category cannot be met
  3. Where an orderly shutdown is essential to protect equipment and personnel
  4. There is adequate assurance that the faulted section will be de-energized in an orderly shutdown

Also, cables with this insulation thickness shall be permitted to be used in 100 or 133 percent insulation level applications where additional insulation strength is desirable.

310.106 Conductors.

  1. Minimum Size of Conductors. The minimum size of conductors shall be as shown in Table 310.106(A), except as permitted elsewhere in this Code.
    Table 310.106(A) Minimum Size of Conductors
    imageMinimum Conductor Size (AWG)Conductor Voltage Rating (Volts)
    CopperAluminum or Copper-Clad Aluminum0–200014122001–5000885001–8000668001–15,0002215,001–28,0001128,001–35,0001/01/0
  2. Conductor Material. Conductors in this article shall be of aluminum, copper-clad aluminum, or copper unless otherwise specified.Solid aluminum conductors 8, 10, and 12 AWG shall be made of an AA-8000 series electrical grade aluminum alloy conductor material. Stranded aluminum conductors 8 AWG through 1000 kcmil marked as Type RHH, RHW, XHHW,THW, THHW, THWN, THHN, service-entrance Type SE Style U, and SE Style R shall be made of an AA-8000 series elec‐ trical grade aluminum alloy conductor material.
  3. Stranded Conductors. Where installed in raceways, conductors 8 AWG and larger, not specifically permitted or required elsewhere in this Code to be solid, shall be stranded.
  4. Insulated. Conductors, not specifically permitted else‐ where in this Code to be covered or bare, shall be insulated.

Informational Note: See 250.184 for insulation of neutral conductors of a solidly grounded high-voltage system.

310.110 Conductor Identification.

  1. Grounded Conductors. Insulated or covered grounded conductors shall be identified in accordance with 200.6.
  2. Equipment Grounding Conductors. Equipment ground‐ ing conductors shall be in accordance with 250.119.
  3. Ungrounded Conductors. Conductors that are intended for use as ungrounded conductors, whether used as a single conductor or in multiconductor cables, shall be finished to be clearly distinguishable from grounded and grounding conduc‐ tors. Distinguishing markings shall not conflict in any manner with the surface markings required by 310.120(B)(1). Branch- circuit ungrounded conductors shall be identified in accord‐

ance with 210.5(C). Feeders shall be identified in accordance with 215.12.

Exception: Conductor identification shall be permitted in accordance with 200.7.

310.120 Marking.

  1. Required Information. All conductors and cables shall be marked to indicate the following information, using the appli‐ cable method described in 310.120(B):
    1. The maximum rated voltage.
    2. The proper type letter or letters for the type of wire or cable as specified elsewhere in this Code.
    3. The manufacturer’s name, trademark, or other distinctive marking by which the organization responsible for the product can be readily identified.
    4. The AWG size or circular mil area.Informational Note: See Conductor Properties, Table 8 of Chap‐ ter 9, for conductor area expressed in SI units for conductor sizes specified in AWG or circular mil area.
    5. Cable assemblies where the neutral conductor is smaller than the ungrounded conductors shall be so marked.
  2. Method of Marking.
    1. Surface Marking. The following conductors and cables shall be durably marked on the surface. The AWG size or circu‐ lar mil area shall be repeated at intervals not exceeding 610 mm (24 in.). All other markings shall be repeated at inter‐ vals not exceeding 1.0 m (40 in.).
      1. Single-conductor and multiconductor rubber- and thermoplastic-insulated wire and cable
      2. Nonmetallic-sheathed cable
      3. Service-entrance cable
      4. Underground feeder and branch-circuit cable
      5. Tray cable
      6. Irrigation cable
      7. Power-limited tray cable
      8. Instrumentation tray cable
      1. Marker Tape. Metal-covered multiconductor cables shall employ a marker tape located within the cable and running for its complete length.Exception No. 1: Type MI cable. Exception No. 2: Type AC cable.Exception No. 3: The information required in 310.120(A) shall be permitted to be durably marked on the outer nonmetallic covering of Type MC, Type ITC, or Type PLTC cables at intervals not exceeding 1.0 m (40 in.).Exception No. 4: The information required in 310.120(A) shall be permitted to be durably marked on a nonmetallic covering under the metallic sheath of Type ITC or Type PLTC cable at intervals not exceed‐ ing 1.0 m (40 in.).Informational Note: Included in the group of metal-covered cables are Type AC cable (Article 320), Type MC cable (Article 330), and lead-sheathed cable.
      2. Tag Marking. The following conductors and cables shall be marked by means of a printed tag attached to the coil, reel, or carton:
      1. Type MI cable
      2. Switchboard wires
      3. Metal-covered, single-conductor cables
      4. Type AC cable
      (4) Optional Marking of Wire Size. The information required in 310.120(A)(4) shall be permitted to be marked on the surface of the individual insulated conductors for the following multiconductor cables:
      1. Type MC cable
      2. Tray cable
      3. Irrigation cable
      4. Power-limited tray cable
      5. Power-limited fire alarm cable
      6. Instrumentation tray cable
  3. Suffixes to Designate Number of Conductors. A type letter or letters used alone shall indicate a single insulated conductor. The letter suffixes shall be indicated as follows:
    1. D — For two insulated conductors laid parallel within an outer nonmetallic covering
    2. M — For an assembly of two or more insulated conduc‐ tors twisted spirally within an outer nonmetallic covering
  4. Optional Markings. All conductors and cables contained in Chapter 3 shall be permitted to be surface marked

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