Conduits: Electrical Metallic Tubing and Rigid Metal Conduit PDF

Here's the converted markdown format from the image or document you provided: ## Conduits ### What is a conduit? * Electrical conduit is a raceway or piping system that protects wires and cables from impact, moisture, and vapors. * It is a path for either power or communication (low voltage) electrical wiring. * It is usually tubular and made of metal (galvanized steel, stainless steel, aluminum) or non-metallic materials (plastics) and is either rigid or flexible. * Special types of conduit are required for wet areas and hazardous areas. ### What is a conduit? * Two main categories of conduit body are considered here: metal conduits and non-metal conduit. * Conduit systems can be differentiated by their wall thickness, mechanical stiffness, and tubing material. * Conduit materials are often chosen for their mechanical protection, corrosion resistance, and the overall installation cost. The image shows four circles. The leftmost circle is labeled NPS, then the next circle is labeled OD, then the next is labeled ID, and the rightmost circle is labeled WT. ### The advantages of all types of conduit are that they: * Protect electrical wires from damage due to abuse or accident * Can allow for cables to be easily pulled to inaccessible areas in the future (i.e. inside finished walls) * Allow wiring changes to be made simpler and safer * Can be made waterproof or submersible * Can be sealed to provide protection from fire and explosion hazards ## Electrical Metallic Tubing (EMT) The image shows an example of METAL CHANNEL SUPPORT, RIGID METAL TUBING and SCREW-SET CLAMP FITTING The image shows a couple of Electrical Metallic Tubings * EMT is an unthreaded, thin-wall metal tubing generally made of coated steel, though it may be made of aluminum. * It is a popular choice for electrical conduit in commercial buildings, but is generally not used in residential buildings. * EMT is connected together using clamp-type fittings that slide onto the tubing and then are secured with a set-screw. Electrical Metal Tubing is less expensive and 40% lighter than GRC. * While EMT provides a good amount of protection for the cables inside, it should not be used in hazardous areas where it is exposed to sever damage (like power plants or around vehicular traffic.) * EMT is not suitable for wet areas or where corrosive fumes and vapors exist – special corrosive-resistant tubing and gasketed clamps are required in these areas. * Like RMC, the cut ends of the tubing must be reamed to remove all sharp edges. * Some electricians are skeptical of using EMT in critical areas because the set-screws in the clamps can loosen over time. In order to prevent this, a torque wrench or driver can be used to be sure the screws are set to the correct tension as required by the manufacturer. | Method of Wiring | Uses Permitted | Uses Not Permitted | Bends | Size and Marking | Securing and Supporting | Construction | | --- | --- | --- | --- | --- | --- | --- | | Article 3.58 Electrical Metallic Tubing: Type EMT An unthreaded thin wall raceway of circular cross section designed for the physical protection and routing of conductors and cables and for use as an equipment grounding conductor when installed utilizing appropriate fittings. EMT is generally made of steel (ferrous) with protective coatings or aluminum (nonferrous). | (a) Exposed and Concealed. The use of EMT shall be permitted for both exposed and concealed work. (b) Corrosion Protection. Ferrous or nonferrous EMT elbows, couplings, and fittings shall be permitted to be installed in concrete, in direct contact with the earth, or in areas subject to severe corrosive influences where protected by corrosion protection and judged suitable for the condition. (c) Wet Locations. All supports, bolts, straps, screws, and so forth shall be of corrosion-resistant materials. | (1) Where, during installation or afterwards, it will be subject to severe physical damage (2) Where protected from corrosion solely by enamel (3) In cinder concrete or cinder fill where subject to permanent moisture unless protected on all sides by a layer of noncinder concrete at least 50 mm thick or unless the tubing is at least 450 mm under the fill (4) In any hazardous (classified) location (5) For the support of luminaries (fixtures) or other equipment except conduit bodies no larger than the largest trade size of the tubing. Where practicable, dissimilar metals in contact anywhere in the system shall be avoided to eliminate the possibility of action | How Made. Bends shall be made so that the tubing is not damaged and the internal diameter of the tubing is not effectively reduced. Number in One Run. There shall not be more than the equivalent of four quarter bends (360 degrees total) between pull points, for example, conduit bodies and boxes. | (a) Minimum. EMT smaller than metric 15 mm shall not be used. (b) Maximum. The maximum size of EMT shall be 100 mm. Marking. EMT shall be clearly and durably marked at least every 3000 mm. | (a) Securely Fastened. EMT shall be securely fastened in place at least every 3000 mm. In addition, each EMT run between termination points shall be securely fastened within 900 mm of each outlet box, junction box, device box, cabinet, conduit body, or other tubing termination. (b) Supports. Horizontal runs of EMT supported by openings through framing members at intervals not greater than 3000 mm and securely fastened within 900 mm of termination points shall be permitted. | Reaming and Threading. (a) Reaming. All cut ends of EMT shall be reamed or otherwise finished to remove rough edges. (b) Threading. EMT shall not be threaded. Grounding. EMT shall be permitted as an equipment Grounding conductor. | ## Rigid Metallic Conduit Example of THREADED COUPLE FITTING, THREADED RIGID METAL TUBING and METAL CHANNEL SUPPORT * RMC is a thick-walled, threaded tubing. * It is generally made of coated steel, stainless steel, or aluminum. * The conduit is connected together by screwing connectors to the main tubes. * Rigid metal conduit provides significant protection from impacts and other damage. * It can be used as a grounding conductor for short runs, but it is best practice to use wiring that has a grounding wire. The thicker walls of RMC protects the cables inside from electromagnetic * interference (EMI), which can be harmful to sensitive equipment. * RMC can be made corrosion-resistant by applying a coating such as PVC or by galvanizing the metal. The corrosion protection resists damage from water or other chemicals that can degrade metal. There are three common types of corrosion treatment: * Galvanized Rigid Conduit (GRC), which is the most popular form of RMC, is used in commercial and industrial buildings. * PVC-coated aluminum, which is suitable where chemical fumes that are corrosive to steel are present. * Bronze alloy, which is suitable for coastal areas, chemical plants, oil refineries and underwater situations. PVC-coated rigid steel, which is resistant to oils, grease, acids, alkalis, and moisture and is flame-retardant. * When cut, the ends of rigid metal conduit should be reamed (remove burrs and rough edges) to protect the wire insulation from abrasion. In addition, any fittings should match the type of metal used for the conduit tubing to prevent problems from galvanic action. * There are two main disadvantages to using rigid metal conduit. * First, since all connections are threaded, there is much more labor required when installing the system – this makes RMC much more expensive. * Second, the thick walls of the tubing make the conduit much heavier, which also makes installation more labor intensive and expensive. | Method of Wiring | Uses Permitted | Uses Not Permitted | Bends and markings | Size and Marking | Securing and Supporting | Construction | | --- | --- | --- | --- | --- | --- | --- | | Article 3.44 Rigid Metal Conduit: Type RMC A threadable raceway of circular cross section designed for the physical protection and routing of conductors and cables and for use as an equipment grounding conductor when installed with its integral or associated coupling and appropriate fittings. RMC is generally made of steel (ferrous) with Protective coatings or aluminum (nonferrous). Special use types are silicon bronze and stainless steel | (a) All Atmospheric Conditions and Occupancies. Shall be permitted under all atmospheric conditions and occupancies. Ferrous raceways and fittings protected from corrosion solely by enamel shall be permitted only indoors and in occupancies not subject to severe corrosive influences. (b) Corrosion Environments. RMC, elbows, couplings, and fittings shall be permitted to be installed in concrete, in direct contact with the earth, or in areas subject to severe corrosive influences where protected by corrosion protection and judged suitable for the condition. (c) Cinder Fill. RMC shall be permitted to be installed in or under cinder fill where subject to permanent moisture where protected on all sides by a layer of non-cinder concrete not less than 50 mm thick; where the conduit is not less than 450 mm under the fill; or where protected by corrosion protectiion and judged suitable for the condition. (d) Wet Locations. All supports, bolts, straps, screws, and so forth, shall be of corrosion-resistant materials or protected against corrosion by corrosion-resistant materials | (a) Atmospheric Conditions and Occupancies. Shall be permitted under all atmospheric conditions and occupancies. Ferrous raceways and fittings protected from corrosion solely by enamel shall be permitted only indoors and in occupancies not subject to severe corrosive influences. | Bends – How Made. Bends of RMC shall be so made that the conduit will not be damaged and so that the internal diameter of the conduit will not be effectively reduced. The radius of the curve of any field bend to the centerline of the conduit shall not be less than indicated in Table 2, Chapter 9. Bends– Number in One Run. There shall not be more than the equivalent of four quarter bends (360 degrees total) between pull points, for example, conduit bodies and boxes. | (a) Minimum. RMC smaller than 15 mm shall not be used. (b) Maximum. RMC larger than 150 mm shall not be used. Marking. Each length shall be clearly and durably identified in every 3 000 mm. Standard Lengths. The standard length of RMC shall be 3000 mm, including an attached coupling, and each end shall be threaded Longer of shorter lengths with or without coupling and threaded or unthreaded shall be permitted | Securing and Supporting. RMC shall be installed as a complete system and shall be securely fastened in place and supported in accordance below (a) Securely Fastened. RMC shall be securely fastened within 900 mm of each outlet box, junction box, device box, cabinet, conduit body, or other conduit termination. Fastening shall be permitted to be increased to a distance of 1 500 mm where structural members do not readily permit fastening within 900 mm. Where approved, conduit shall not be required to be securely fastened within 900 mm of the service head for above-the-roof termination of a mast. (b) Supports. RMC shall be supported in accordance with one of the following: Conduit shall be supported intervals not exceeding 3 000 mm. The distance between supports for straight runs of conduit supports prevent transmission of stresses to terminations where conduit is deflected between supports | Reaming and Threading. All cut ends shall be reamed or otherwise finished to remove rough edges. Where conduit is threaded in the field, a standard cutting die with a 1 in $16$ taper shall be used. Bushings. where a conduit enters a box, fitting, or other enclosure, a bushing shall be provided to protect the wire from abrasion unless the design of the box, fitting, or enclosure is much as to afford equivalent protection. (Threadless couplings and connectors shall be made be tight. Where buried masonry or concrete, threadless couplings and connectors shall comply with .14 2 .1(a).Threadless couplings and connectors shall not be used on threaded conduit ends unless listed for the purpose. Running Threads. Running threads shall not be used on conduit for connection at couplings. Grounding. PMC shall be permitted as an equipment grounding conductor | | | | (3) Exposed vertical risers fromindustrial machinery or fixedequipment shall be permitted to besupported at intervals not exceeding$6000$ mm if the conduit is made upwith threaded couplings, the conduitis supported and securely fastened atthe top and bottom of the riser, andno other means of intermediatesupport is readily available.(4) Horizontal runs of RMCsupported by openings throughframing members at intervals notexceeding 3 000 mm and securelyfastened within 900 mm oftermination points shall bepermitted. | | | | | --- | --- | --- | --- | --- | --- | --- | Table 3.44.2.21(b)(2) Supports for Rigid Metal Conduit | Conduit Size (mm) | Maximum Distance Between Rigid Metal Conduit Supports (mm) | | ---- | ---- | | 15-20 | 3000 | | 25 | 3600 | | 32-40 | 4200 | | 50-65 | 4800 | | 80 and larger | 6000 | ## Intermediate Metallic Conduit * As its name suggests, Intermediate Metal Conduit (IMC) has walls that are thinner than RMC, but thicker than EMT. * Thus the weight of IMC also falls between RMC and EMT. Intermediate Metal Conduit is threadable, but it can also be un-threaded and used with clamp-type fittings. * IMC is generally made from steel and can be coated. | Method of Wiring | Uses Permitted | Size | Securing and Supporting | Construction | | ---- | ---- | ---- | ---- | ---- | | Article 3.42 INTERMEDIATE METAL CONDUIT TYPE IMC A steel threadable raceway of circular cross section designed for the physical protection and routing of conductors and cables and for use as an equipment grounding conductor when installed with its integral or associated coupling and appropriate fittings. | (a) All Atmospheric Conditions and Occupancies.Use of IMC shall be permitted under all atmospheric conditions and occupancies. (b) Corrosion Environments.IMC elbows, couplings, and fittings shall be permitted to be installed in concrete, in direct contact with the earth, or in areas subject to severe corrosive influences where protected by corrosion protection and judged suitable for the condition. (c) Cinder Fill.IMC shall be permitted to be installed in or under cinder fill where subject to permanent moisture where protected on all sides by a layer of noncinder concrete not less than 50mm thick; where the conduit is not less than 450 mm under the fill; or where protected by corrosion protection and judged suitable for the condition. (d) Wet Locations.All supports, bolts, straps, screws, and so forth shall be of corrosion-resistant materials or protected against corrosion by corrosion-resistant materials. | (a) Minimum.IMC smaller than raceway size 15 mm shall not be used. (b) Maximum.IMC larger than 100 mm shall not be used. Standard Lengths.The standard length of IMC shall be 3 000 mm , including an attached coupling, and each end shall be threaded MarkingEach length shall be clearly and durably marked at least every 1 500 mm with the letters IMC. Each length shall be marked BendsNumber in One Run.There shall not be more than the equivalent of four quarter bends (360 degrees total) between pull points, for example, conduit bodies and boxes | (a) Securely Fastened.Each IMC shall be securely fastened within 900 mm of each outlet box, junction box, device box, cabinet, conduit body, or other conduit termination. Fastening shall be permitted to be increased to a distance of 1500 mm where structural members do not readily permit fastening within 900 mm. Where approved, conduit shall not be required to be securely fastened within 900 mm of the service head for above-the-roof termination of a mast. (b) Supports.IMC shall be supported in accordance with one of the following: (1) Conduit shall be supported at intervals not exceeding 3 000 mm. (2) Exposed vertical risers from industrial machinery or fixed equipment shall be permitted to be supported at intervals not exceeding 6 000 mm if the conduit is made up with threaded couplings, the conduit is supported and securly fastened and no other means of intermediate support is readily available. (3) Horizontal runs of IMC supported by openings through framing members at intervals not exceeding 3 000 mm and securely fastened within 900 mm of termination points shall be permitted. | Dissimilar Metals. Where practicable, dissimilar metals in contact anywhere in the system shall be avoided to eliminate the possibility of galvanic action. Aluminium fittings and enclosures shall be permitted to be used with IMC. Reaming and Threading. All cuts ends shall be reamedor otherwisefinished to remove rough edges. Where conduit is threaded in the field, a standard cutter with a taper of 1 in 16 shall be used. Bushings. Where a conduit enters a box, fitting, or other enclosure, a bushing shall be provided to protect the wife from abrasion unless the design of the box, fitting, or enclosure is such as to afford equivalent protection. | ## Flexible Metallic Conduit Image shows a Electrical Wiring installation with a Flexible Metallic Conduit in a commercial setting. * Flexible metal conduit (FMC) is typically available in diameters between 3/8" and 3", but larger sizes can sometimes be found. * It is made by coiling self-interlocked aluminum or steel strips, which forms a hollow tube that wires can be pulled through. * FMC comes in a standard wall (sometimes called full wall) thickness or a reduced wall thickness. * Most manufacturers also produce an extra-flexible FMC for tighter bend radiuses, but this is generally not UL approved. * Standard FMC is recommended in dry areas where it would be impractical to install EMT or other non-flexible conduit, yet where metallic strength to protect conductors is still required. * Because of its flexibility, the FMC can help reduce vibrations from passing from motor to structure through the conduit. | Method of Wiring | Uses Permitted | Uses Not Permitted | Bends andMarkings | Size andMarking | Securing and Supporting | | ---- | ---- | ---- | ---- | ---- | ---- | | Article 3.48 Flexible Metal Conduit: Type FMC A raceway of circular cross section made of helically wound, formed, interlocked metal strip. | FMC shall be permitted to be used in exposed and concealed locations | (1) In wet locations unless the conductors are approved for the specific conditions and the installation is such that liquid is not likely to enter raceways or enclosures to which the conduit is connected (2) In hoistways (3) In storage battery rooms (4) In any hazardous (classified) location (5) Where exposed to materials having a deteriorating effect on the installed conductors, such as oil or gasoline (6) Underground or embedded in poured concrete or aggregate (7) Where subject to physical damage | There shall not be more than the equivalent of four quarter bends (360 degrees total) between pull points, for example, conduit bodies and boxes. | MinimumFMC less than 15 mm shall not be used. (a) Minimum, FMC larger than raceway size 100 mm shall not be used. | Securely FastenedFMC shall be securely fastened in place by an approved means within 300 mm of each box, cabinet, conduit body, or other conduit termination and shall be supported and secured at intervals not to exceed1 400 mm. SupportsHorizontal runs of FMC supported by openings through framing members at intervals not greater than 1 400 mmand securely fastened within 300 mmoftermination points shall be permitted | | Method of wiring | Uses Permitted | Uses Not Permitted | Bends | SIze and Marking | Construction | | ---- | ---- | ---- | ---- | ---- | ---- | | Article 3.60 FLEXIBILEMETALLIC TUBUNG: TYPE FMT A raceway that is circular in cross section, flexible, metallic, and liquighttight with a nomemtallic jacket. | (1) In dry locations (2) where concealed (3) In accessible locations (4) for system voltages of 1 000 volts maximum | (1) In hoistways (2) In storage battery rooms (3) In hazardous (classified) locations unless otherwise permitted under this code (4) Under ground for direct earth burial, or embedded in poured concrete or aggregrate (5)Where subject to physical damage (6) In lengths over 1800 mm | | (a) Minimum. FMT smaller than raceway size 15 mm shall not be used. (b) Maximum. The maximum size of FMT shall be raceway 20 mm | Number of Conductors (a) Raceway size 15 mm and 20 mm. The number of conductor in raceway size 15 mm shall not exceed the that permitted by the percentage field specified in Table 9.1.1.1 (b) Metric Designers. 12 (Trade Size) the number of conductors in raceway size mm shall not exceed is that permitted in Table 3.48.2.13 grounding FMT shall be permitted as an equipment grounding conductor where installed in accordance 2.50.6.9(7) | | | | | Table 3.60.2.15(a) Minimum Radius for Flexing Use Raceway Size (mm) Minimum Radius (mm) 10 250 15 310 20 440 | | | | | | | | | | | | | | Table 3.60. 2.15(b) Minimum Radius for Fixed Bend Raceway Size (mm) Minimum Radius (mm) | | | | | | | 10 90 (mm) 15 100 20 125 | | | | | | | Tabl 9. 1.1.1 Percent of Cross Section of Conduit and Tubing for Conduictors Number of Conduictors All Conductors 1 53 2 31 Over 2 40 | | | ### Electrical Non-Metallic Tubing (ENT) * ENT is a thin-walled corrugated tubing that is flexible so it can be bent without special tools, however it will not permanently hold the bend. * It is easier to install than RNC because it can be routed around obstructions without cutting and welding the pipe. * Special ENT connectors are used – these are generally snap-in connections and are not watertight. | Method of Wiring | Uses Permitted | Uses Not Permitted | Bends | Size and Marking | Securing and Supporting | Construction | | --- | --- | --- | --- | --- | --- | --- | | Article 3.62 Electrical Normentaltiic Tubing: TYPE ENT A nonmetallic plisable corrugated raceway of circular cross section with integral or associated couplings, connecturs, and frriings for the installation of electric conductors. ENT composed a manterial that is resistant to moisture and chemical atmospheres ans id flame retardent Apliable raceway is a raceway that can be bent by handwith ara reasonable force bat withiout pother assistance. | (1) In any building not exceeding three floors above grade as follows: a. For exposed work, b. concealed within walls, floors, and ceilings (2) In any building exceeding thress floors above grade, ENT shall be concealed within walls, floors and ceilings where the walls floors and ceilings provide a thermal barries of material that has at least a 15-minule finish (3) In locations subject to severe corrosive infleuencew (4) in concealed ary and damp focations (5) Above suspended ceilings where the suspended ceiling provide a thermal barrier of material that has at least a 15-minute finish rating | (1) In hazardous (classified) locations (2) For the support of luminaries ( fixtures) and other equipment (3) where subject to ambient to ambient temperatures in excess of 50 degree C unless listed otherwise (4) For conductors or cables operating at a temperature higher than the ENT listed temperature rating For direct earth burial (6) where the Voltage is over 600 volis (7) in exposed Locations (8) in theaters and Similar Locations (9) Where exposed to the direct rays of the sun. (10) Where subject to physical damage | Number in One Run there shall not be more the equivalent of four (360 over pull points the equivalent of quarter Bends is, for example, conduit bodies and boxes | Minimum ENT smaller than 15 mm shall not be used.Maximum ENT larger than 50 and shall not be usedmarking ENT shall be be used shall be clearly and durably marked at least every 3000 and shall not | ENT shall be installed as a complete system Securely Fastened ENT shall be securly fastened at Intervals not exceeding 900 mm in addition EMT shall be Securely fasted in plate within 900 and an outlet box Device box junction 809 cabinet, where il terminates Supports Horizontal runs of supported by Qpenings in framing members at Intervals not exceeding 900 mm and Security fastened within 920 mm of terminations Points shall be permitted | Grounding where a equipment grounding Is required that a separate equipment grounding. Conducter shall be Installed in the racewayENT shall be made of material that does not exceed the ignitiblity flanmability Simoke 3300. and toxically Characterticsof rigid ENT. as a- pre wired Manifactured assembly shall Be provided be in continuous Lengths Capabea of shipping. | (6) Encased in poured concrete, or embedded in a concrete slab on grade where ENT is placed on sand or approved screenings, provided fittings identified for this purpose are used for connections. (7) For wet locations indoors as permitted in this section or in a concrete slab on or below grade, with fittings listed for the purpose. (8) Raceway size 15 mm through 25 mm as listed manufactured pre-wired assembly. ### Rigid Non Metallic Conduit (RNC) * RNC is the lightest conduit available and is generally the least expensive. * Fittings slipped onto the tubing and welded with a solvent, which is faster than the fittings used in metal conduits. In addition, the welded joints are water-tight. * Plastic conduit can be heated with special tools so that it can be bent in the field. * RNC Pipe is most commonly available as schedule 40 or schedule 80 pipe, but can also be manufactured in other sizes and wall thicknesses. | Feature | Schedule 40 PVC Pipe | Schedule 80 PVC Pipe | | --------- | ----------------------- | ---------------------- | | Wall Thickness | Thinner | Thicker | | Pressure Rating | Lower | Higher | | Durability | Less durable | More durable | | Cost | Less expensive | More expensive | * The main disadvantages are that plastic conduit will not stand up to impacts as well as metal conduits. In addition, plastic conduits cannot be used for grounding, so a grounding conductor will need to be pulled along with the other conductors. Finally, plastic conduit expands and contracts more than metal conduit when exposed to heat, which needs to be taken into account when designing long runs. | Method of wiring | Uses Permitted | Uses Not permitted | Bends | Size and Marking | Securing and supporting | Construction | | ---- | ---- | ---- | ---- | ---- | ---- | ---- | | Article 3.52 Rigid Non metallic Conduit Type Rnc | (a) concealed. Rnc shall permitted in watts, floors and ceilings | (a) Harzardous location-(1) un Harzardous location | bends- Haw made Show in table 2 chapter 9 | a minimum Rnc smaller than (1) is my bends and one run (b) material and one run | (a) the support the not fast | The other is the best | This Is Very Important | |(b) corrosive Influence Rnc shall permitted is location subject to where subject to chemical For which Materials | (b) support of Laminates and future For support Materials or the equipment | then number | Maximum Rnc Length The Rne Material This Is one | This and and this And this | All This Is Here And This Here This One | 3 3 3 3 3 3 3 3 3 | is here at all | (c) This (c) physical damage where subject to physical such | than Material of of of | is the Very Is Very Good Great Amazing Fantastic is for | The where Is is great good very Amazing | This where where where is The great is Is Is Good is there

Conduits: Electrical Metallic Tubing and Rigid Metal Conduit PDF

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