Nonmetallic-sheathed cable is probably the the very least expensive that the miscellaneous wiring methods. That is relatively lightweight and easy to install. That is widely used for apartment unit installations ~ above circuits of 600 volts or less. FIG. 10 shows an instance of a stripper used for stripping nonmetallic-sheathed cable. A razor knife additionally works fine with care. The environment of nonmetallic-sheathed cable must con type to the demands of NEC short article 334. Describe FIGs. 11, 12, 13, 14, 15, and also 16.

• The cable need to be strapped or stapled not an ext than 12 in. (300 mm) from a crate or fitting.

• do not staple flat nonmetallic-sheathed cables on edge, FIG. 15.

• uneven run with horizontal feet or notches in studs and joists, the intervals in between straps or staples should not exceed 4 1/2 ft (1.4 m).

• Exposed runs of cables deserve to be subjected to lots of abuse. A child might pull or stand on the cables and adults might use the cables come hang points on.

NEC 334.15 needs that cables it is in protected versus physical damages where necessary. For example, where exposed in a garage with open up studs, run the cables ~ above the political parties of the studs. Whereby cables space run horizontally from or through stud come stud, security is required.

Some assessors require protective boards end exposed horizontal cable runs, or sheet rock, or other wall surface finish up to the ceiling, or at the very least 7 ft (2.13 m) up. For protection of cables in attics, see ar 15.

• The 4 1/2 ft (1.4 m) securing need is not needed where nonmetallic-sheathed cable is run horizontally v holes in hardwood or steel framing members (studs, joists, rafters, etc.). The cable is taken into consideration to be adequately supported by the frame members, NEC 334.30(A).

• The inner sheet of the bend shall have a mini mum radius not less than 5 time the cable diameter, NEC 334.24.

• The cable must not be supplied in circuits of much more than 600 volts.

• CAUTION: Be very careful when installing staples. Driving them too hard can squeeze and also damage the insulation ~ above the conductors, causing quick circuits and/or soil faults.

• check out FIG. 11 for special problems when utilizing single-gang nonmetallic an equipment boxes.

• Nonmetallic-sheathed cable must be safeguarded where passing with a floor by at the very least 6 in. (150 mm) of rigid steel conduit, intermediate steel conduit, electric metallic tubing, Schedule 80 rigid PVC conduit, or various other approved means, NEC 334.15(B). A fitting (bushing or connector) must be provided at both ends of the conduit to safeguard the cable indigenous abrasion, FIG. 12.

• when nonmetallic-sheathed cables are "bundled" or "stacked" for ranges of an ext than 24 in. (600 mm) without maintaining spacing, their ampacities must be decreased (adjusted, derated) follow to Table 310.15(B)(3)(a). When cables room bundled together, the heat generated by the conductors cannot quickly dissipate. View FIG. 13(A).

• When an ext than two nonmetallic-sheathed cables are installed through the very same opening in hardwood framing members that are to it is in fire- or draft-stopped v thermal insulation, caulk, or sealing foam, and also there is no spacing in between the cables, your conductor ampacities candlestick be readjusted according come NEC Table 310.15(B)(3)(a). Check out NEC 334.80 and FIG. 13(B).

• When form AC and type MC cables space "bundled" or "stacked" without keeping spacing, derating is not essential if the following is true:

- The conductors are 12 AWG copper.

You are watching: When armored cable is used what protection is provided at the cable ends

- The bundling or stacking is not much more than 24 in. (600 mm).

- There are no an ext than three present carrying conductors in every cable.

- There room no much more than 20 current-carrying conductors in the bundle.

When over there are much more than 20 existing carrying conductors in the bundle, because that a length better than 24 in. (600 mm) a 60% adjustment factor shall it is in applied. Check out NEC 310.15(B)(3)(a)(4) and (B)(3)(a)(5).

• type NM cable may be operation in unsupported lengths the not an ext than 4 1/2 ft (1.4 m) in between the last allude of assistance of the cable and a luminaire or other devices within an available ceiling. For this last 4 1/2 ft (1.4 m), the 12-in. (300-mm) and 4 1/2-ft (1.4-m) securing demands mentioned over are not crucial if the nonmetallic-sheathed cable is provided as a luminaire (fixture) whip to affix luminaires of various other equipment; watch NEC 334.30. Luminaire (fixture) whips are disputed in section 7 and also Section 17.

FIG. 16 shows the installation of nonmetallic sheathed cable in unfinished basements and crawl spaces, 334.15(C).

See section 15 and Figures 13 and Figure 14 for additional text and also diagrams covering the surroundings of cables in attics.

FIG. 11 shows the Code requirements for securing nonmetallic-sheathed cable when using nonmetallic boxes.

The code in 314.40(D) calls for that all steel boxes have actually provisions because that the attachment of an tools grounding conductor. FIG. 17 shows a gang-type move (device) box that is tapped for a screw through which the ground connection conductor might be associated underneath. FIG. 18 mirrors an outlet box, also with provisions because that attaching grounding conductors. FIG. 19 illustrates the usage of a tiny grounding clip.

NEC 410.44 calls for that there be a provision by which the equipment grounding conductor deserve to be attached to the exposed metal parts that luminaires.

FIG. 17 Gang-type move (device) box.

FIG. 18 Outlet box.

FIG. 19 method of attaching ground clip to a steel switch (device) box; watch 250.148.

Are Cables allowed in Raceways?

Yes, yet only if certain conditions are met.

NEC 300.15(C) permits using a detailed conduit or tubing without a box whereby the conduit or pipe is offered to defend a nonmetallic-sheathed cable versus physical damage. FIG. 20 shows an instance of this in a basement wherein the wiring method in the ceiling is NM cable and a switch or receptacle is in a box placed on the wall. One EMT is set up from the box to a point over the ceiling joists, where the EMT is secured to the side of the joists. The NM cable is then operation inside the EMT, and an insulating installation is installed on the upper finish of the tube to defend the cable against abrasion. The cable go not call for securing within the raceway, 334.30. The finished job is neat.

The conductors inside a nonmetallic-sheathed cable meet all of the UL needs for form THHN conductors however are no surface marked in any manner.

NEC 334.15(B) requires protection of nonmetallic sheathed cable indigenous physical damages where necessary.

This section lists different types of raceways allow ted come be provided for defense of the cable.

The raceway fill for a cable in a conduit or tubing is based upon the allowable percent fill values specified in Table 1, section 9.

Alternate technique of installation NM above Panel Nonmetallic-sheathed cables are usually secured to a panel, box, or cabinet, through a cable clamp or connector. For surface-mounted enclosures only, 312.5(C), Exception, gives an alternate an approach for to run nonmetallic-sheathed cables, as depicted in FIG. 21.

FIG. 20 an instance of EMT protecting a nonmetallic-sheathed cable from physical damages where the cable is run down the wall of an loose basement. This also makes a succinct installation.

The EMT and the steel box must be grounded. Physical protection and grounding are required by 334.15(C). NEC 300.18(A), Exception, also recognizes this type of installation.

Be aware of a significant rule in keep in mind 9 come NEC Table 1 of ar 9. This note requires the if cables with elliptical overcome sections are installed in a raceway, the cross-sectional area that the cable is established by suspect the greater measurement is the diameter that a circle. This preeminence is needed because some installers execute not straighten the cables prior to installing them v the race method but pull them out of the facility of a carton, which results in the cables twisting inside the raceway.

Let"s execute a calculation utilizing a 12-2 W/G form NM cable that is 1/4 in. 3 1/2 in. In size. We will assume the 1/2 in. Dimension is the diameter of a circle and perform the calculation using the following formula:

A = pi x r^2

A = 3.14159 x (0.25 x 0.25)

A = 3.14159 x 0.0625

A = 0.1963 Sq.In.


FIG. 21 an alternate an approach for to run nonmetallic-sheathed cables into a surface-mounted panel. This is permitted for surface-mounted panels only, 312.5(C), Exception.

Nonmetallic-sheathed cable secured in ~ 12 in. (300 mm) from wherein it emerges from raceway.

Raceway comes out of optimal of panelboard and also must not permeate structural ceiling.

A fitting is required on both ends to stop abrasion. The fitting(s) should be easily accessible after installation.

Raceway have to be sealed to avoid debris from acquiring into panelboard.

Outer sheath the cable must expand into panelboard at least 1/4 in. (6 mm).

Secure the raceway.

Do not exceed percent to fill as shown in Table 1, section 9, NEC. Usage largest dimension of cable together its diameter for calculating the cable"s cross-sectional area, section 9, Table 1, keep in mind 9.

If raceway is no over 24 in. (600 mm): preferably cable to fill is 60%. Derating conductor ampacity is no necessary. If raceway is over 24 in. (600 mm): maximum cable to fill is 40%.

Derating conductor ampacity is necessary.

NEC 310.15(B)(3)(a)(2), and also Section 9, Table 1, note 4.


Let"s look in ~ the complying with table to recognize how countless of these cables us are allowed to install in various sizes the EMT and also whether derating is required.

Be sure to comply with all the conditions stated in NEC 312.5(C) Exception. Additionally be aware kind NM cable is restricted to surroundings in dried locations and also thus the installation in EMT as described above is not permitted in wet or wet locations.

Identifying Nonmetallic-Sheathed Cables One quite thing about nonmetallic-sheathed cable, an especially that with a white outer jacket, is the at panelboards and an equipment and outlet boxes, you deserve to use a permanent noting pen to mark the external jacket through a few words describe what the cable is for. Examples: feeding TO ATTIC; feed TO L.R.; feed TO DINING ROOM RECEPTACLES; feeding TO PANEL; BC#6; TO various other 3-WAY SWITCH; switch LEG to CEILING LIGHT; TO external LIGHT; and also so on.

By noting the cables as soon as they are installed, confusion once making the relationships is reduced considerably.

Another great idea is to make a sleeve by cutting turn off a quick 2 in. Size of NM cable, pulling the end the conductors, then noting an identifying statement ~ above the sleeve. Slide the sleeve over the certain conductors within the panel or box.

Multifamily Dwellings

Nonmetallic-sheathed cable is permitted to be installed in one- and two-family dwellings and in multifamily residences where the structure construction is type III, kind IV, or type V; see 334.12(A). Meanings of construction types are discovered in structure codes, the navard of this text, and in Annex E of the NEC.

For years, the NEC restricted nonmetallic sheathed cable come a maximum of three floors above finished grade. This limitation was gotten rid of in the 2002 NEC.

FIG. 22 (A) kind AC cable (Note paper wrap) (B) type MC cable (AFC Cable Systems, Inc., new Bedford, MA)


Table 12 to compare of kind AC and form MC cables.


Type AC (Article 320) article 320: This article contains all of the installation demands for the installation of form AC armored cable.

320-1. Definition: form AC cable is a fabricated assembly of insulated conductors in a versatile interlocked metallic armor.

Number that Conductors: two to 4 current-carrying conductors add to bonding wire. That may additionally have a separate devices grounding conductor.

Conductor Size and Type: 14 AWG through 1 AWG because that copper conductors.

12 AWG v 1 AWG for aluminum conductors will be significant " AL " ~ above a sign on the carton or reel.

12 AWG v 1 AWG because that copper-clad aluminum conductors will be significant " AL (CU-CLAD)" or "Cu-Clad Al" on a tags on the carton or reel.

Color Coding: Two-conductor: one black, one white.

Three-conductor: one black, one white, one red.

Four-conductor: one black, one white, one red, one blue.

These are in addition to any equipment grounding and bonding conductors.

Bonding & Grounding: type AC cable shall provide an adequate path for fault current. Kind AC cable has a bonding wire or strip.

Bonding cable is in constant direct contact with the metal armor. The bonding wire and also armor act with each other to serve as the acceptable devices ground. The bonding wire does not need to be terminated, simply folded earlier over the armor. FIG. 23 shows how the bonding piece is folded earlier over the armor.

Never usage the bonding strip as a grounded neutral conductor or as a separate equipment grounding conductor. It is an interior bonding strip-nothing more! Insulation: type ACTHH has actually 90°C thermoplastic insulation, by much the most common.

Type ACTH has actually 75°C thermoplastic insulation. Type AC has thermo collection insulation.

Type ACHH has actually 90°C thermoset insulation.

Conductors room individually wrapped v a fire retardant fibrous cover: irradiate brown Kraft paper.

Author"s comment: This is one easy way to distinguish type AC from type MC.

Armor: Galvanized stole or aluminum. Armored cable with aluminum armor is marked "Aluminum Armor."

Covering over armor: none Locations: okay for dried locations.

Not it s okay for wet or wet locations.

Not okay for straight burial.

Insulating bushings: compelled to defend conductor insulation native damage. Referred to as "antishorts," this keep any type of sharp steel edges that the armor from cutting the conductor insulation. Usually supplied in a bag through cable.

FIG. 23(A) reflects an antishort gift inserted.

FIG. 23(B) shows the recommended way of bending the bonding strip over the antishort to organize the antishort in place.

Minimum radius of bends: 53 diameter that cable. For tiny size cables, this is about the very same curvature together a soda can.

Not available with "super neutral conductor." Not accessible with fiber-optic cables.

Support: Not more than 4½ ft (1.4 m) apart.

Not an ext than 12 in. (300 mm) from crate or fitting.

Support not required where cable is fished with walls and ceilings.

Cables operation horizontally through holes in studs, joists, rafters, etc., are thought about supported by the framing members.

Support not required when offered as a fixture whip within an available ceiling for lengths not over 6 ft (1.8 m) indigenous last point of support.

Voltage: 600 volts or less.

Ampacity: usage the 60°C shaft of Table 310.15(B)(16). Derating allowed from 90°C column.

Thermal insulation: If buried in heat insulation, the conductors have to be rated 90°C.

Connectors: set screw-type connectors not permitted with aluminum armor. Provided connectors are perfect for grounding purposes.

UL conventional 4. Due to the fact that UL requirements have advanced in numerical order, it is apparent that the armored cable standard is among the an initial standards to be developed.



Type MC (Article 330)

Article 330: This write-up contains all of the installation demands for the surroundings of form MC metal-clad cable.

330.1. Definition: form MC cable is a factory assembly of one or more insulated circuit conductors with or without optical fiber members and enclosed in an armor that interlocking metal tape or a smooth or corrugated metallic sheath.

Number the Conductors: Any variety of current-carrying conductors. At the very least one manufacturer has actually a "Home operation Cable" that has conductors for an ext than one branch circuit, to add the tools grounding conductors.

Conductor Size and Type: 18 AWG with 2000 kcmil because that copper conductors.

12 AWG v 2000 kcmil for aluminum or copper-clad aluminum conductors.

12 AWG through 2000 kcmil for copper-clad aluminum conductors will be marked " AL (CU-CLAD)" or "Cu-Clad Al" ~ above a tags on the carton or reel.

Color Coding: Two-conductor: one black, one white.

Three-conductor: one black, one white, one red.

Four-conductor: one black, one white, one red, one blue.

These are in enhancement to any kind of equipment grounding and also bonding conductors.

Bonding & Grounding: This has actually a separate eco-friendly insulated tools grounding conductor. The may have actually two equipment grounding conductors for isolated soil requirements, such together for computer system wiring.

Unless specifically listed for grounding, the coat of MC cable is no to be used as an equipment grounding conductor.

The sheath of smooth or corrugated tube type MC is provided as acceptable together the required devices grounding conductor.

Some MC cables have a complete size bare aluminum conductor in continuous, direct contact with the steel armor. This ceiling conductor and the metal armor act together to serve as the acceptable devices ground.

Cut off the bare conductor in ~ the armor.

Insulation: kind MC has actually 90°C thermoplastic insulation.

Some form MC has actually thermoset insulation.

Type MC cable is accessible with a PVC outer jacket perfect for direct burial.

No separation, personal, instance wrap. Has a polyester (Mylar) ice over all conductors. Some constructions have the extra class of Mylar tape end the separation, personal, instance conductors. Has no bare bond wire yet may have actually a full-size aluminum grounding/ bonding conductor. Author"s comment: These room easy ways to distinguish form AC from form MC.

Armor: Galvanized steel, aluminum, or copper.

Three types:

Interlocked (most common). Needs a separate equipment grounding conductor. The armor by itself is not an acceptable devices grounding conductor. Stole or aluminum.

Smooth tube. Walk not call for a separate tools grounding conductor. Aluminum only.

Corrugated tube. Go not call for a separate equipment grounding conductor. Copper or aluminum.

Covering over armor: obtainable with PVC external covering.

Suitable for wet locations, for direct burial and concrete encasement if therefore covered.

Locations: okay for wet places if therefore listed.

Okay for direct interment if therefore listed.

Okay come be set up in a raceway.

Insulating bushings: Recommended yet not compelled to defend conductor insulation native damage. Normally in a bag supplied with cable.

Minimum radius of bends: Smooth Sheath:

• 103 because that sizes no over ¾ in. (19 mm) in diameter.

• 123 for sizes over ¾ in. (19 mm) and also not over 1½ in. (38 mm) in diameter.

• 153 because that sizes over 1½ in. (38 mm) in diameter.

Corrugated or interlocked:

• 73 diameter of cable.

Available through "super neutral conductor" when forced for computer branch-circuit wiring. For example, three 12 AWG and one 10 AWG neutral conductor.

Available with power conductors and fiber-optic cables in one cable.

Support: Not more than 6 ft (1.8 m) apart.

Not an ext than 12 in. (300 mm) from box or fitting for cables having four or fewer 10 AWG or smaller sized conductors.

Support not needed where cable is fished through walls and also ceilings.

Cables operation horizontally v holes in studs, joists, rafters, etc., are taken into consideration supported by the framing members.

Support not required when offered as a fixture whip within an obtainable ceiling for lengths no over 6 ft (1.8 m) native last allude of support.

Voltage: 600 volts or less. Some MC has a voltage rating no to exceed 2000 volts.

Ampacity: comparable to cable pulled in raceways, determine in accordance with 310.15.

Thermal insulation: No cite in NEC. Type MC has actually 90°C thermoplastic insulation.

Connectors: collection screw-type connectors not permitted with aluminum armor. Detailed connectors are suitable for grounding purposes.

UL conventional 1569.



FIG. 23 Anti-short bushing prevents cutting that the conductor insulation through the sharp steel armor.


Type AC and type MC cables look an extremely much the same (FIG. 22), yet there are far-reaching differences.

Table 12 compares several of these differences.

To remove the outer steel armor, a rotary armor-cutting tool favor that presented in FIG. 24 might be used.

If a hacksaw is used, make an angle cut on one of the armor"s convolutions as lengthy as the conductors must be, probably 10-12 in. Be cautious not to reduced too deep or you could cut into the conductor insulation. Bending the armor in ~ the cut and snap it off. Then slide the 10-12 in. That armor off the end of the cable. This technique is not recommended through cable manufacturers because of the danger of damage to the insulated conductors. Watch FIG. 25.

FIG. 24 This is an instance of a tool that specifically cuts the external armor of armored cable, making it easy to remove the armor through a few turns the the handle. (Seatek Co., Inc.)

FIG. 25 utilizing a hacksaw to cut through a increased convolution the the cable armor. This method is no recommended by manufacturers due to the hazard of damaging the conductors through cutting too deeply.

Most electricians, as soon as using armored cable, will certainly make three cuts through their hacksaw. The middle cut is wherein the cable and also conductors will certainly be cut off completely. The very first and third cuts are where the armor will certainly be snap off. This saves time due to the fact that it in reality prepares two ends the the cable.

Most electricians still describe armored cable together BX, supposedly acquired from one abbreviation that the Bronx in brand-new York City, where armored cable was when manufactured. BX was a trademark own by the General electric Company, but over the year it has end up being a generic term.

FIG. 22 shows armored cable through the armor eliminated to display the conductors that are wrapped with document and the bare bonding wire.

Table 13 mirrors the uses and also installation needs for form AC and form MC cables because that residential wiring.

Table 13 Uses and also installation in residences (Type AC and kind MC).

INSTALLING CABLES through WOOD and METAL framing MEMBERS (300.4)

Wood construction

When wiring a house, nonmetallic-sheathed cables space run v holes drilled in studs, joists, and also other framing members. Typically, holes space drilled in the approximate centers of wood framing members. Come avoid possible dam age to the cables, make certain that the edge of the feet is at least 1 1/4 in. (32 mm) native the nearest edge of the framing member, 300.4(A)(1). Refer to FIG. 26.

You have probably noticed the a 2 x 4 procedures 1 1/2 in. 3 x 1/2 in., and that a 2 x 3 actions 1 1/2 in. X 2 1/2 in. This can existing a actual problem!

Steel Plates

If the 1 1/4 in. (32 mm) from the leaf of hole to the edge of frame member can not be maintained, or if the cable is set in a notch, a steel plate(s) at least 1/16 in. (1.6 mm) thick need to be provided to protect the cable from errant nails or drywall screws, 300.4(A)(1). In all situations where the NEC requires 1/16-in. (1.6-mm) stole plates, detailed and marked steel plates are allowed to be less than 1/16 in. (1.6 mm) due to the fact that they have actually passed difficult mechanical tests.

This permission is uncovered in 300.4(A)(1) exemption 2, 300.4(A)(2) exemption 2, 300.4(B)(2) Exception, 300.4(D) exception 3, and 300.4(E) exception 2.

See FIG. 26.

Instead of making use of steel plates, FIG. 27 illustrates gadgets that have the right to be provided to stand off the cables native a frame member.

FIG. 26 approaches of protecting nonmetallic and also armored cables for this reason nails and also screws that "miss" the studs will not damages the cables, 300.4(A)(1) and also (2). Since of your strength, intermediate and rigid steel conduit, PVC strict conduit, and electrical metallic tubing space exempt native this rule per the Exceptions discovered in 300.4. See FIG. 28 for alternate methods that protecting cables.

FIG. 27 gadgets that deserve to be supplied to meet the Code necessity to keep a 1¼-in. (32-mm) clearance from frame members.

FIG. 28 whereby it is vital to overcome pipes or other comparable obstructions, make it impossible to preserve at least 1¼-in. (32-mm) clearance native the frame member come the cable, download a steel plate(s) at least 1/16-in. (1.6 mm) thick to protect the cable from feasible damage from nails or screws.

See 300.4(A)(1) and also (A)(2).

Cables set up Parallel to framing Members or Furring Strips

To defend nonmetallic-sheathed cables, armored cables, or nonmetallic raceways that room run parallel to framing members or furring strips from being damaged by drywall screws and nails, you have actually two choices: (1) keep them much more than 1 1/4 in. (32 mm) indigenous the nearest edge of the framing member or furring strip, or (2) usage steel plates. Refer to 300.4(D), 320.17, and also 334.17. Check out FIGs. 16, 26, 27, and also 28.

Metal Construction

Metal studs space being used much more and more. Castle don"t burn and also termites don"t eat them. They are stronger 보다 wood and can be set 20 in. (500 mm) on center instead of the usual 16-in. (400-mm) spacing.

Metal studs are 10 times an ext conductive than wood, so therapy of insulation must be addressed.

Where nonmetallic-sheathed cables pass v holes or slot in steel framing members, the cable should be safeguarded by a provided bushing or provided grommet securely fastened in place prior to installation the cable. The bushing or grommet shall:

• remain in place during the wall finishing process,

• sheathe the complete opening, and

• be detailed for the objective of cable protection.

This details is uncovered in 300.4(B)(1) and also 334.17. Check out FIG. 29. Bushings the snap into a hole sized because that the specific size bushing (1/2 in., 3/4 in., etc.), or a two-piece snap-in bushing the fits just about any dimension precut feet in the steel framing members are acceptable come use, as displayed in FIG. 29. These varieties of bushings (insulators) room not compelled in metal framing members when the wiring method is armored cable, EMT, FMC, or electric nonmetallic tubing.

When to run nonmetallic-sheathed cable or electric nonmetallic pipe through steel framing members whereby there is a likelihood that nails or screws might be driven into the cables or tubing, a stole plate, steel sleeve, or steel clip at least 1/16 in. (1.6 mm) thick must be mounted to defend the cables and/or tubing. This is spelled the end in 300.4(B)(2). View FIGs. 28 and also 29.

FIG. 29 NEC 300.4(B) and also 334.17 require defense of nonmetallic-sheathed cable whereby it runs through holes in metal framing members. Displayed are two types of detailed bushings (grommets) that have the right to be set up to protect nonmetallic-sheathed cable from abrasion. Electricians normally avoid making use of nonmetallic-sheathed cable through steel studs and joists. Castle use electric metallic tubing, flexible metal conduit, armored cable (Type AC or MC), or electrical nonmetallic tubing. Wherein there is a likelihood the nails or screws could penetrate the nonmetallic-sheathed cable, 1/16-in. (1.6-mm) thick stole plates, sleeves, or clips have to be mounted to protect the cable or electric nonmetallic tubing.


NEC 300.4(F) addresses the wiring problems associated with cutting grooves into structure material due to the fact that there is no hollow space for the wiring. Nonmetallic-sheathed cable and also some raceways should be safeguarded when to adjust in a groove.

Protection have to be noted with a 1/16-in. (1.6-mm) stole plate(s), sleeve, or equivalent, or the groove need to be deep enough to allow not much less than 1 1/4-in. (32-mm) complimentary space because that the whole length of the groove. This situation can be encountered where styrofoam insulation structure blocks are grooved to receive the electrical cables, then extended with wallboard, lumber paneling, or other finished wall material. An additional typical instance is whereby solid timber planking is set up on top of lumber beams.

The peak side of the planking is extended with roofing material, and also the bottom next is exposed and serves together the perfect ceiling. The only means to install wiring for ceiling luminaires and also fans is to groove the planking in some manner, as shown in FIG. 30.

This additional protection is not forced when the raceway is intermediate metal conduit (Article 342), rigid steel conduit (Article 344), rigid PVC conduit (Article 352), or electric metallic tube (Article 358) (see FIG. 29).

NEC 334.30(B)(1), and also 300.4(D), exemption 2, allow cables to be "fished" between outlet crate or other access points without additional protection.

FIG. 30 example of just how a solid hardwood framing member or Styrofoam insulating block might be grooved to get the nonmetallic sheathed cable. After ~ the cable is to adjust in the groove, a stole plate(s) not much less than 1/16-in. (1.6-mm) thick need to be installed over the groove to protect the cable native damage, such as from thrust nails or screws. Check out 300.4(F) and 334.15(B).

In the recreation room that the residence plans, precautions need to be taken so over there is adequate security for the wiring. The wall surfaces in the recreation room space to be paneled. Therefore, if the carpenter offers 1 x 2 or 2 x 2 furring strips, together in FIG. 31, nonmetallic-sheathed cable would call for the extr 1/16-in. (1.6-mm) steel plate(s) security or the use of was standing off devices comparable to those illustrated in FIG. 27.

Some structure contractors attach 1-in. Insulation to the walls, then build a 2 x 4 wall surface in former of the basement structural structure wall, leaving 1-in. Spacing between the insulation and the back side of the 2 x 4 studs. This makes it straightforward to operation cables or conduits behind the 2 x 4 studs and also eliminates the need for the additional mechanical protection, as displayed in FIG. 32.

FIG. 31 once 1 x 2 or 2 x 2 furring strips are mounted on the surface ar of a basement wall, added protection, as presented in FIGs. 26, 27, 29, and also 30, need to be provided. The is difficult to maintain the minimum distance of 1¼ in. (32 mm) native the nearest sheet of the frame member, in which case protection is forced the whole length of the cable run, 300.4(D).

FIG. 32 This sketch shows just how to insulate a foundation wall and also how to construct a wall that offers a space to run cables and/or raceways that will certainly not require the extr protection as shown in FIGs. 26, 27, 29, and 30.

FIG. 33 once 2 x 4 studs are set up "flat," such as could be uncovered in nonbearing partitions, cables running parallel to or v the studs have to be protected against the possibility of having nails or screws pushed through the cables. This way protecting the cable v 1/16-in. (1.6-mm) steel plates or identical for the entire length that the cable, or installation the wiring making use of intermediate metal conduit, rigid steel conduit, strict PVC conduit, or EMT. View FIGs. 26, 27, 28, and 29.

Watch out for any wall partitions wherein 2 x 4 studs are mounted "flat," together in FIG. 33. In this case, the an option is to administer the forced mechanical security as forced by 300.4, or to download the wiring in EMT.

See ar 15 worrying the environment of cables in attics.

Building Codes

When adhering to the NEC, be sure to additionally comply with the structure code. Building codes are came to with the weakening of frame members as soon as drilled or notched. Conference the requirements of the NEC have the right to be in conflict with building codes and also vice versa. Here is a recap of several of the crucial building password requirements found in the ICC global Residential Code.


• cut or notches in exterior or bearing partitions shall not exceed 25% of the stud"s width.

• cut or notches in nonbearing partitions shall no exceed 40% that the stud"s width.

• boring or drilled feet in any kind of stud:

- shall not be higher than 40% the the stud"s width,

- shall not be closer 보다 5/8 in. (15.9 mm) come the leaf of the stud, and

- shall not be located in the same section together a cut or notch.


• Notches top top the top or bottom that joists shall no exceed 1/6 the depth of the joist, shall not be much longer than 1/3 the broad of the joists, and also shall no be in the middle 3rd of the joist.

• Holes bored in joists shall no be in ~ 2 in.

(50 mm) the the height or bottom of the joist or any kind of other hole, and also the diameter of any such hole shall not exceed 1/3 the depth of the joist. If the joist is also notched, the feet shall no be closer 보다 2 in. (50 mm) to the notch.

Engineered lumber Products

Today, we find plenty of homes created with engineered wood I-joists and also beams. The strength of these factory-manufactured frame members conforms come various structure codes. It is an essential that specific precautions it is in taken loved one to drilling and cutting these products so as no to threaten them. In general:

• execute not cut, notch, or drill feet in trusses, laminated veneer lumber, glue-laminated members, or I-joists unless specifically permitted by the manufacturer.

• do not cut, drill, or notch flanges. Flanges room the top and bottom pieces.

• perform not reduced holes also close to support or to other holes.

• for multiple holes, the lot of web to be left in between holes must be at least twice the diameter of the largest nearby hole. The net is the piece in between the flanges.

• Holes no over 1 1/2 in. (38 mm) usually can be drilled everywhere in the web.

• perform not hammer on the web except to eliminate knockout pre-scored holes.

• Check and follow the manufacturer"s instructions!


NEC 300.22 is incredibly strict regarding what species of wiring methods are allowed for environment of cables through ducts or plenum chambers. These stringent rules are for fire safety.

The Code demands are somewhat calm by 300.22(C), Exception. In this exception, permission is given to operation nonmetallic-sheathed and armored cables in joist and also stud spaces (i.e., cold wait returns), yet only if they are run perpendicular to the long dimensions of together spaces, as portrayed in FIG. 34.

FIG. 34 Nonmetallic-sheathed cable may pass with cold air return, joist, or stud spaces in dwellings, however only if it is operation at best angles come the long dimension of the space, 300.22(C), Exception.

FIG. 35 Cable connectors.


The connectors shown in FIG. 35 are offered to fasten nonmetallic-sheathed cable and also armored cable to manufacturer"s installation instructions, the particular NEC article, and the UL White Book.

Grounding. All noted fittings for noted metallic raceways and listed metal jacketed cables are tested to bring a stated amount that fault present for a specified length of time, do the fittings expropriate able for grounding when properly installed.

In this residence, the wiring method for every one of the exposed wiring in the workshop is come be electric metallic tube (EMT). Wiring through EMT is spanned in information in section 18.

Table 14 offers a review of the requirements for installing intermediate metal conduit (IMC), rigid steel conduit (RMC), strict polyvinyl chloride conduit (PVC), and also electrical metallic tubing (EMT).


The environment of some devices requires functional connections, both to simplify the installation and to stop the deliver of vibrations. In residential wiring, flexible relationships are used to connect equipment such as attic fans, food rubbish disposers, dishwashers, air conditioners, warm pumps, and also recessed luminaires.

the boxes and also panels in which lock terminate. This connectors clamp the cable securely to every outlet box. Numerous boxes have built-in clamps and do not call for separate connectors.

The question proceeds to it is in asked: May an ext than one cable be inserted in one connector? unless the UL listing of a particular cable connector shows that the connector has been tested for usage with more than one cable, the dominion is one cable, one connector. Connectors perfect for an ext than one cable will certainly be significant on the carton.

Table 14 Conduit and tubing.

FIG. 36 Code demands for securing and also supporting raceways are discovered in 342.30 (intermediate metal conduit), 344.30 (rigid steel conduit, 352.30 (rigid PVC conduit), and 358.30 (electrical metallic tubing).

Table 15 preferably distance in between supports for rigid PVC conduit.


Some areas do not permit cable wiring.

They require that the wiring technique be a raceway- metallic or nonmetallic. Girlfriend will have to inspect this out before starting a project.

The adhering to comparison chart gives the highlights the the NEC needs for different varieties of raceways that could be used in a residence. For much more detailed information, describe the adhering to Table 16 reflects the NEC demands for three varieties of frequently used versatile conduit.

Table 16 versatile connections.


Electrical nonmetallic pipe (ENT) is covered in short article 362 that the NEC. The is a pliable, lightweight, corrugated raceway made of PVC. It needs fittings made especially for the ENT. FIG. 44 shows color-coded ENT and some fittings. Color-coded ENT can be provided to identify power, communication, and fire protection signaling system.

Although not regularly used in typical house wiring, part electricians find ENT an extremely practical for providing a raceway system for installation structured wiring conductors and also cables. Structured wiring is questioned in section 31.

FIG. 37 (A) Flexible metal conduit.

(B) Liquidtight flexible metal conduit.

(C) Liquidtight flexible nonmetallic conduit. (Electri-Flex Co.)


Service-entrance cable is covered in short article 338 the the NEC.

Service-entrance cable is defined as a single conductor or multi-conductor assembly detailed with or without an all at once covering, primarily used for services.

Where allowed by local electric codes, service-entrance cable is most frequently run indigenous the utility"s business drop (service point) to the meter base, then from the meter basic to the main business panelboard.

It is additionally permitted together a branch circuit come connect significant electrical appliances and as a feeder to a subpanel. Four-wire cable with 3 insulated conductor and also a bare equipment grounding conductor is required for feeders come panelboards as well as to appliances such as electric ranges and also dryers. Because that these situations, the selection of even if it is to use kind SE cable or nonmetallic-sheathed cable i do not care a issue of choice, the significant issue gift the price of the cable. Some form SE cable v aluminum conductors may expense less than that for nonmetallic sheathed cable through copper conductors. The job for the environment of either kind is the same.

FIG. 38 various fittings for (A) flexible steel conduit, (B) liquidtight flexible metal conduit, and also (C) liquidtight flexible nonmetallic conduit.

FIG. 39 If FMC or LFMC are serving together an tools ground return path, the full length shall not exceed 6 ft (1.8 m). Describe 250.118(5)c, and also 250.118(6)d.

FIG. 40 The "combined" size of flexible steel conduit and also liquidtight flexible steel conduit shall no exceed 6 ft (1.8 m) to offer as a ground return path, 250.118(5)c, and 250.118(6)d.

There room two layouts of form SE cable: SER and SEU. Table 17 shows the NEC environment requirements and also the crucial differences in construction of these cables. Watch Table 17 and FIG. 45.

FIG. 41 use of liquidtight flexible metal conduit or versatile liquidtight nonmetallic conduit.

FIG. 42 few of the an ext common areas where flexible onnections could be used.


FIG. 43 grounding capabilities of liquidtight flexible steel conduit (LFMC).

Permitted together a grounding way if that is no over trade dimension 1 1/4, is not over 6 ft (1.8 m) long, and also is linked by fittings listed for grounding. The 6 ft (1.8 m) length contains the complete length that any and also all flexible relations in the run. See FIG. 41.

Minimum trade dimension 1/2. Trade size 3/8 allowed as a luminaire fixture) whip no over 6 ft (1.8 m) long.

When used as the grounding means, the preferably overcurrent machine is 20 amperes for profession sizes 3/8 and 1/2, and 60 amperes for profession sizes 3/4, 1, and 1 1/4.

Not an ideal as a grounding means under any type of of the following conditions:

- profession sizes 1 1/2 and also larger

- profession sizes 3/8 and 1/2 when overcurrent maker is better than 20 amperes

- trade sizes 3/8 and 1/2 when longer than 6 ft (1.8 m)

- profession sizes 3/4,1, and 1 1/4 when overcurrent device is better than 60 amperes

- profession sizes 3/4, 1, and 11/4 when longer than 6 ft (1.8 m)

For this conditions, install a different

Equipment ground connection conductor sized per Table 250.122.


FIG. 44 Color-coded ENT, a coupling, a threaded connector, and a snap-in connector.

Table 17 Service-entrance cables type SE, SER, SEU, and also USE comparisons.

Type UF Cable (Article 340)

Type UF is an secret feeder and branch circuit cable. Kind UF cable is disputed in ar 16.

FIG. 45 type SEU service-entrance cable. The major characteristic is the uninsulated wraparound neutral conductor.

See Table 17 for NEC demands for the permitted supplies of form SE cables.

FIG. 46 form SER service-entrance cable.

The major characteristics are the insulated neutral conductor and bare equipment grounding conductor. Check out Table 17 because that NEC requirements for the permitted provides of form SE cables.


Note: describe the code or the plans where necessary.

1. The largest size hard conductor allowed to be installed in a raceway is (10 AWG) (8 AWG) (6 AWG). One the exactly answer.

2. What is the minimum branch-circuit wire dimension that might be mounted in a dwelling?

3. What exceptions, if any, space there to the price for question 2?

4. What identify the ampacity of a wire?

5. What unit of measure up is provided for the diameter the wires?

6. What unit of measurement is offered for the cross-sectional area the wires?

7. What is the voltage rating the the conductors in type NMC cable?

8. Indicate the allowable ampacity the the following type THHN (copper) conductors.

Refer to Table 310.15(B)(16).

a. 14 AWG ______ amperes

b. 12 AWG ______ amperes

c. 10 AWG ______ amperes

d. 8 AWG ______ amperes

e. 6 AWG ______ amperes

f. 4 AWG ______ amperes

9. What is the maximum operation temperature the the complying with conductors? offer the prize in levels Celsius.

a. Type XHHW __

b. Type THWN __

c. Type THH __

d. Form TW ____

10. What room the color of the conductors in nonmetallic-sheathed cable for:

a. 2-wire cable? ______ , ______

b. 3-wire cable? ______ , ______ , ______

11. Because that nonmetallic-sheathed cable, may the uninsulated conductor be provided for purposes various other than grounding?

12. What size devices grounding conductor is provided with the adhering to sizes that nonmetallic-sheathed cable?

a. 14 AWG __

b. 12 AWG __

c. 10 AWG __

d. 8 AWG ___

13. Under what condition may nonmetallic-sheathed cable ( kind NM) be fished in the hole voids of masonry block walls?

14. A. What is the maximum distance permitted in between straps top top a cable installation?

b. What is the maximum street permitted in between a box and the an initial strap in a cable installation?

c. Walk the NEC allow 2-wire Romex stapled top top edge?

d. When kind NMC cable is run with holes in studs and joists, must added support be provided?

15. What is the difference between form AC and kind ACT armored cables?

16. Form ACT armored cable may be bent come a radius that not less than ______ time the diameter that the cable.

17. Once armored cable is used, what defense is noted at the cable ends?

18. What protection have to be listed when installation a cable in a notched stud or joist, or as soon as a cable is run through bored holes in a stud or joist whereby the street is less than 1 1/4 in. (32 mm) native the sheet of the framing member come the cable, or wherein the cable is run parallel to a stud or joist and also the distance is less than 1 1/4 in. (32 mm) native the sheet of the framing member to the cable?

19. Because that installing directly in a concrete slab, (armored cable) (nonmetallic-sheathed cable) (conduit) may be used. Circle the correct technique of installation.

20. One the correct answer come the complying with statements:

a. Form SE service-entrance cable is because that aboveground use. True | False

b. Type USE service-entrance cable is perfect for direct burial in the ground. True | False

c. Form SE cable with an uninsulated neutral conductor is allowed for hooking increase an electrical range. True |False

d. Form SE cable with an insulated neutral conductor is permitted for hooking increase an electrical range. True | False

e. Are varieties SE and also USE service-entrance cables offered in your area? correctly | No

21. As soon as running NMC with a bored hole in a stud, the nearest sheet of the boring hole shall no be less than ______ in. From the face of the stud uneven the cable is protected by a 1/16 in. (1.6 mm) steel steel plate(s).

22. Where is the key service-entrance panel situated in this residence?

23. A. Is nonmetallic-sheathed cable permitted in your area because that residential wiring? b. Native what source is this information obtained?

24. Is it allowed to usage flexible steel conduit end 6 ft (1.8 m) in size as a grounding means? (Yes) (No) one the exactly answer.

25. Liquidtight flexible metal conduit may serve as a grounding way in sizes up to and including ______ in. Where offered with noted fittings.

26. The allowable current-carrying capacity (ampacity) that aluminum wire, or the best overcurrent defense in the situation of 14 AWG, 12 AWG, and 10 AWG conductors, is less than the of copper cable for a offered size, insulation, and tempera ture that 30°C. Describe Table 310.15(B)(16) and also 240.4(D) and complete the complying with table. Important: wherein the ampacity of the conductor does not enhance the rating that a traditional fuse or circuit breaker as provided in 240.6(A), 240.4(B) patent the choice of the following "higher" conventional rating of fuse or circuit breaker if the next greater standard rating does no exceed 800 amperes. Nonstandard ampere ratings are also permitted.

27. It is permissible for an electrician to attach aluminum, copper, or copper-clad aluminum conductors with each other in the very same connector. (True) (False) one the exactly answer.

28. Terminals the switches and also receptacles significant CO/ALR are perfect for use with ____, ____, and ____ conductors.

29. Cable connectors marked AL/CU are suitable for use through ______, ______, and also ______ conductors.

30. A wire connector bearing no noting or referral to AL, CU, or ALR is perfect for use v (copper) (aluminum) conductors only. One the exactly answer.

31. When kind NM or NMC cable is run through a floor, it should be protected by at least ______ in. (______ mm) of ___

32. Once nonmetallic-sheathed cables space bunched or bundled together for ranges longer than 24 in. (600 mm), what happens to their current-carrying ability?

33. In diagrams A and also B, nonmetallic-sheathed cable is run through the cold wait return. Which diagram "meets Code"? A ______ B ______ check one.

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34. The noting on the external jacket that a nonmetallic-sheathed cable suggests the letters NMC-B. What walk the letter "B" signify?

35. A 120-volt branch circuit gives a resistive heating load of 10 amperes. The distance from the panel to the heater is around 140 ft. Calculation the voltage drop using (a) 14 AWG, (b) 12 AWG, (c) 10 AWG, (d) 8 AWG copper conductors. Watch 210.19(A), Informational note No. 4 and 215.2(A)(3), Informational note No. 2.

36. In inquiry 35, it is wanted to save the voltage drop come 3% maximum. What mini mum dimension wire would certainly be mounted to achieve this 3% maximum voltage drop? view 210.19(A), Informational note No. 4 and also 215.2(A)(3), Informational keep in mind No. 2.

37. NEC 215.2, 220.61, 230.42, and 310.15(B)(7) state the the neutral conductor that a residential organization or feeder deserve to be smaller than the phase conductors, yet only ____

38. The allowable ampacity the a 4 AWG THHN from Table 310.15(B)(16) is 95 amperes.

What is this conductor"s ampacity if linked to a terminal detailed for use with 60°C wire?

39. If, since of part obstruction in a wall space, the is difficult to store an NMC cable at the very least 1 1/4 in. (32 mm) native the leaf of the stud, then it candlestick be safeguarded by a metal plate at least ____ in. Thick.

40. The recessed fluorescent luminaires mounted in the ceiling of the recreation room of this residence are associated with trade size 3/8 flexible steel conduit. These flexible relationships are commonly referred to together fixture whips. Does the flexible metal conduit provide adequate grounding for the luminaires, or need to a separate devices grounding conductor it is in installed?

41. Flexible liquidtight metal conduit will certainly be provided to attach the air-conditioner unit. It will be trade size 3/4. Have to a separate tools grounding conductor be set up in this FLMC to ground the waiting conditioner properly?

42. What dimension overcurrent device protects the air-conditioning unit?

43. Might the 20-ampere small-appliance branch circuits in the kitchen the a residence also supply the lighting above the kitchen sink and under-cabinet lighting? inspect the correct answer. Correctly ______ No ______

44. A 30-ampere branch circuit is mounted for one electric clothes dryer. What is the maxi mum ampere rating that a dryer allowed by the NEC to be cord-and-plug-connected come this circuit? inspect the correct answer.

a. ______ 30 amperes

b. ______ 24 amperes

c. ______ 15 amperes

45. In plenty of areas, metal framing members room being supplied in residential construction.

When making use of nonmetallic-sheathed cable, what have to be offered where the cable is run v the steel framing members?

46. Space set-screw-type connectors permitted to be supplied with armored cable that has actually an aluminum armor?

47. Many armored cable today has actually 90°C conductors. What is the correct designation for this form of armored cable?

48. If you saw two different types of SE cables, exactly how would you identify them?

49. Circle the correct answer specifying the kind of location:

a. A raceway mounted underground (Dry) (Wet)

b. A raceway installed in a concrete slab that is in direct call with the earth (Dry) (Wet)

c. A raceway installed in a concrete slab in between the first and 2nd floor (Dry) (Wet)

d. A raceway mounted on the outside of a structure exposed to the weather (Dry) (Wet)

e. The inner of a raceway installed on the exterior of a building exposed to the weather (Dry) (Wet)