1、An AmericAn nAtionAl StAndArdNECA/NACMA 120-2012 Standard forInstalling Armored Cable (AC) and Metal-Clad Cable (MC)Published byNational Electrical Contractors AssociationJointly developed withNACMAStandard forInstalling Armored Cable (AC)and Metal-Clad Cable (MC)NECA/NACMA 120-2012An AmericanNation
2、al StandardPublished byNational Electrical Contractors AssociationJointly developed withNACMATMnullNOTICE OF COPYRIGHTThis document is copyrighted by NECAReproduction of these documents either in hard copy or soft (including posting on the web) is prohibited without copyright permission. For copyrig
3、ht permission to reproduce portions of this document, please contact NECA Standards hospitals, nursing homes, limited care facilities, clinics, medical and dental offices, and ambulatory care facilities, whether permanent or movableNo YesIn other than patient care areas of hospitals, for mechanical
4、protection of emergency system (critical and life-safety branches) where fishedYes Yes7 nStandard for Installing Armored Cable (AC) and Metal-Clad Cable (MC) NECA/NACMA 120Type of AC CableWhere not subject to physical damage, Type AC cable is permitted to be installed:Without insulated equipment gro
5、unding conductorWith insulated equipment grounding conductorIn patient care areas of hospitals, for mechanical protection of emergency system (critical and life-safety branches) where fishedNo YesIn patient care areas of nursing homes, limited care facilities, clinics, medical and dental offices, an
6、d ambulatory care facilities hospitals, for wiring of life safety and critical branchesNo YesAreas of nursing homes and limited care facilities wired in accordance with Chapters 1 through 4 of the NEC where the areas are used exclusively as patient sleeping roomsYes YesIn assembly occupancies, fire-
7、rated construction Yes YesIn assembly occupancies, non fire-rated constructionYes YesFor theaters, audience areas of motion picture and television studios, performance areas, and similar locations, fire-rated constructionNo YesFor theaters, audience areas of motion picture and television studios, pe
8、rformance areas, and similar locations, non fire-rated constructionYes YesFor motion picture and television studios and similar locations, permanent wiring of stage or setNo YesFor cranes and hoists (dry locations only) No YesFor elevators, dumbwaiters, escalators, moving walks, wheelchair lifts and
9、 stairway chair liftsYes YesFor information technology equipment, under raised floorsYes Yes4.4 Uses Not PermittedType AC cable is not permitted to be installed: As service-entrance conductors. Where subject to physical damage unless protected by conduit or tubing In damp or wet locations In air voi
10、ds of masonry block walls where the walls are exposed to or are subject to excessive moisture or dampness Where exposed to corrosive conditions Embedded in plaster finish on brick or other masonry in damp or wet locations4.5 Connectorsa) AC cable connectors. Fittings for connecting Type AC cable are
11、 required to be marked as suitable for such use. The identification is either on the smallest container in which the product is packaged or is on the connector itself. Select the appropriate size of n 8NECA/NACMA 120 Standard for Installing Armored Cable (AC) and MetalClad Cable (MC)cable connector
12、for the trade size of the cable. Some connectors are suitable for connecting two cables. The reference in the UL White Book for Type AC cable connectors is (AWSX).b) AC cable set-screw connectors. As provided in the UL White Book (AWEZ) for Armored Cable, connectors of the set-screw type are only pe
13、rmitted to be used with cables having steel armor. They are not acceptable on cables with aluminum armor.c) Other connectors. Connectors for Type MC cable and power and control tray cable are also suitable for use with Type AC cable when specifically indicated on the connector or the shipping carton
14、.d) Insulating bushings. Connectors or clamps that connect Type AC cable to boxes or cabinets are designed so the required insulating bushing is visible for inspection after the cable is connected. The insulating bushing is often referred to in trade jargon as a “red head.” e) Grounding. All listed
15、connectors for Type AC cable are suitable for grounding since the armor of Type AC cable serves as the equipment grounding conductor. Remove paint or other insulating material between the enclosure and the connector to ensure a proper grounding connection.Figure 4.5Connectors for Type AC and Type MC
16、 cables.9 n1. Scope5.1 DescriptionType MC cable is a factory assembly of one or more insulated current-carrying conductors and one or more equipment grounding conductors (if required) in an overall metallic sheath. MC cable is manufactured with three different types of armor in the following configu
17、rations:1. Interlocking metal-tape (steel or aluminum) (MCI)2. Interlocking metal-tape (steel or aluminum) Armor ground (MCI-A)3. Smooth metal tube (aluminum only) (MCS)4. Corrugated metal tube (copper or aluminum) (MCC)Type MC cable consists of one or more current-carrying conductors, one or more e
18、quipment grounding conductors if required, and in some cases optical fibers. MC cables containing optical fibers are designated Type MC-OF and are considered composite cables in accordance with NEC Article 770.5.2 Conductorsa) Branch circuits, Feeders, and Services. Type MC cable is permitted to con
19、tain conductors from 18 AWG through 2000 kcmil for copper and 12 AWG through 2000 kcmil for aluminum. Typical branch circuit Type MC cables have copper conductors with THHN, THHN/THWN/THWN-2 or XHHW/XHHW-2 insulation and are suitable for circuits up to 600 volts. Typical feeder and service size Type
20、 MC cables have aluminum or copper conductors with THHN/THWN-2 or XHHW/XHHW-2 insulation and are suitable for circuits up to 600 volts. Higher voltage constructions and other insulation types may be available.b) Medium voltage. Type MV cables are available with conductor insulations rated from 2,400
21、 to 35,000 volts and may be marked for use as Type MC cables. c) Fire alarm. Type MC cables intended for fire alarm/control applications have TFN, TFFN, THHN or other suitable insulation.5.3 Special MC Cable ConfigurationsIn addition to “standard” configurations used for services, feeders and branch
22、 circuits, MC cables are manufactured for the following specific applications:Fire Alarm. This Type MC cable is manufactured with either steel or aluminum armor and contains 18 through 10 AWG copper conductors with TFN, TFFN, or THHN insulation. Other appropriate conductor insulations may be used. I
23、n addition, the cable contains a bare or insulated equipment grounding conductor. Install according to NEC Article 760 or NFPA 72 National Fire Alarm and Signaling Code. Composite Cable. This Type MC-OF cable construction contains electrical power and/or control conductors with one or more optical f
24、iber elements. It is installed in accordance with the NEC Article for the type of power or control conductors involved. Composite Type MC cable is available with a PVC jacket and is suitable for direct burial in earth or in concrete. Composite Type MC cable with electric power conductors is permitte
25、d to have a bare or insulated equipment grounding conductor.Oversize neutral conductors. This Type MC cable has standard size circuit conductors and one or more neutral conductors that are larger than the circuit conductors. This cable is often used to safely 5. Metal-Clad Cables (Type MC)n 10NECA/N
26、ACMA 120 Standard for Installing Armored Cable (AC) and MetalClad Cable (MC)handle excessive neutral harmonic currents caused by nonlinear loads. Nonlinear loads are typically produced in branch circuit and feeder wiring for computers, programmable controllers, electronic/electric discharge lighting
27、, computers and other office machines and other electronic equipment that introduce additive harmonic currents from non-linear switching loads. This MC cable type also has a bare or insulated equipment grounding conductor sized for the typical overcurrent protection permitted by Code for the ungroun
28、ded conductors.Multiple individual neutral conductors. This Type MC cable has a color-coded neutral conductor for each ungrounded branch circuit conductor. Similar to the oversize-neutral-conductor cable, this cable is often used to prevent harmonic currents caused by nonlinear loads that are presen
29、t in multiwire branch circuits. Since each ungrounded conductor has a paired grounded (neutral) conductor, simultaneous disconnecting is not required as is the case for multiwire branch circuits The cable also has a bare or insulated equipment grounding conductor sized for the typical overcurrent pr
30、otection permitted by Code for the ungrounded conductors. (Figure 5.3.1).Homerun. This cable is available in various configurations with multiple sets of branch circuit conductors intended to be installed as multiwire branch circuits. The ungrounded (phase) and neutral conductors are color-coded in
31、sets for identification purposes. If more than three conductors in the cable are considered as “current-carrying,” an adjustment factor must be applied in accordance with NEC 310.15(B)(3)(a). If the conductor insulation is 90C, apply the adjustment factor to the appropriate ampacity in the 90C colum
32、n of Table 310.15(B)(16). Use the 75C column if the conductor insulation is rated 75C. The cable also has an insulated equipment grounding conductor sized for the typical overcurrent protection permitted by Code for the ungrounded conductors.PVC jacketed cable. A PVC jacket is extruded over the stee
33、l or aluminum armor. This construction is suitable for use in dry locations, and where so identified, in damp or wet locations and for direct earth burial. Cable that is identified for direct earth burial is also suitable for encasement in concrete without additional marking. This construction may a
34、lso be identified as “sunlight resistant” and “oil resistant” and for use in cable trays. The cable also has an insulated or bare equipment grounding conductor sized for the typical overcurrent protection permitted by Code for the ungrounded conductors.5.4 Equipment Grounding5.4.1 Interlocking Metal
35、 Tape SheathThe armor of Type MC Cable with an interlocking metal tape sheath (MCI) is not itself suitable as an equipment grounding conductor. The cable includes an equipment grounding conductor which is either bare or insulated. For branch-circuit sizes, the most Figure 5.3.1Multiple Neutral Condu
36、ctors Figure 5.3.2PVC Jacketed Cable (courtesy AFC Cable Systems)11 nStandard for Installing Armored Cable (AC) and Metal-Clad Cable (MC) NECA/NACMA 120common type of equipment grounding conductor is insulated with an unstriped (solid) green color. The armor of Type MC Cable with an interlocking met
37、al tape sheath and a bare aluminum grounding/bonding conductor cabled with the insulated conductors (MCI-A) is suitable as an equipment grounding path. a) Sectioned. Larger sizes of MC cable with interlocking metal tape sheath sometimes have the equipment grounding conductor “sectioned.” This means
38、a large equipment grounding conductor is divided into several smaller conductors, all of the same AWG size. This permits the manufacturer to make the cable of a smaller diameter as the smaller conductors take the place of filler that would otherwise be needed. Unless permitted by the AHJ to be twist
39、ed together and terminated in a single connector, smaller equipment grounding conductors that are sectioned in this way must be connected individually to an equipment grounding terminal bar.b) Isolated ground MC cables. MC cables with an additional equipment grounding conductor are often used for ap
40、plications such as computer or cash register branch circuits. These cables are marked “IG” for “isolated ground.” Each additional equipment grounding conductor has green insulation with either a yellow stripe, or a surface marking, or both.c) Patient care areas. The outer armor of the interlocked me
41、tal sheath Type MC cable (MCI) is not permitted as an equipment grounding conductor. As a result, this type of Type MC cable (MCI) is not permitted as the wiring method in patient care areas of health care facilities. The armor of Type MC Cable with an interlocking metal tape sheath and a bare alumi
42、num grounding/bonding conductor cabled with the insulated conductors (MCI-A) is suitable as an equipment path. As a result, this type of Type MC cable (MCI-A) is permitted as the wiring method for branch circuits on the normal power source in patient care areas of health care facilities.5.4.2 Smooth
43、 or Corrugated SheathThe armor of Type MC cables with smooth or corrugated sheaths, or a combination of the sheath and a supplemental bare or unstriped green insulated conductor, is suitable for use as an equipment grounding conductor. a) Bare equipment grounding conductor or green insulation withou
44、t a stripe. This Type MC cable type has a sheath that is not itself suitable as an equipment grounding conductor. Type MC cable of this construction is not permitted to be used in patient care areas of health care facilities. In addition, it is not suitable for use in isolated equipment ground circu
45、its.b) Green insulated equipment grounding conductor with a yellow stripe. This Type MC cable has a sheath that is suitable for use as an equipment grounding conductor. Cable with this construction is permitted in patient care areas of health care facilities or for isolated equipment grounding circu
46、its. Table 5.5 Uses PermittedWhere not subject to physical damage, Type MC cable is permitted to be installed as follows:CommentsFor services Comply with Article 230For feeders Comply with Articles 215 or 225For branch circuits Comply with the applicable NEC articleFor power, lighting, control and s
47、ignal circuits Comply with the applicable NEC articleIndoors and outdoors Comply with all environmental conditionsn 12NECA/NACMA 120 Standard for Installing Armored Cable (AC) and MetalClad Cable (MC)Where not subject to physical damage, Type MC cable is permitted to be installed as follows:Comments
48、Where exposed or concealed Protect from physical damage where requiredDirectly buried where identified for such use Cables with an overall outer PVC jacket marked for direct burial are suitable for direct burial and concrete encasement. Comply with 300.5 or 300.50 for minimum burial depthIn cable tr
49、ay Comply with Article 392In any raceway Comply with raceway fill in NEC Chapter 9, Table 1As open runs of cable Support properly (see Section 6.1)As aerial cable on a messenger Comply with Article 396. See below for wet locations In hazardous (classified) locations See belowEmbedded in plaster finish on brick or other masonry Dry locations onlyIn wet locations Permitted if: a. the metallic covering is impervious to moisture, orb. a moisture-impervious jacket is provided under the metal covering, orc. the insulated conductors under the metallic covering a
