Conduit Types: EMT, RMC, FMC, and More - Electrical Systems

Here is the transcription of the provided text into a structured markdown format. ## Image Descriptions The first image shows four smaller images within it: - Top-left: A view of orange electrical conduit tubing laying on a concrete foundation in the skeleton of a house. - Top-right: Multiple meta...

Here is the transcription of the provided text into a structured markdown format. ## Image Descriptions The first image shows four smaller images within it: - Top-left: A view of orange electrical conduit tubing laying on a concrete foundation in the skeleton of a house. - Top-right: Multiple metal electrical conduit tubing running parallel to one another. - Bottom-left: A close up view of metal electrical conduits. - Bottom-right: Orange electrical conduit tubing being assembled with an electrical box on a concrete foundation and skeleton of a house. The subsequent images are mostly of text from a presentation titled "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. - 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. | | | | | | :------------------ | :--------------- | :---------------- | :------------- | | NOMINAL PIPE SIZE | OUTSIDE DIAMETER | INNER DIAMETER | WALL THICKNESS | |  |  |  |  | | NPS | OD | ID | 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. - 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) - **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 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. ## Article 3.58 | Method of Wiring | Uses Permitted | Uses Not Permitted | Bends | Size and Marking | Securing and Supporting | Construction | | :------------------ | :----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | :---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | :------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | :------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | :----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | :----------------------------------------------------------------------------------------------------------------------------------------------------- | | Article 3.58 | a) Exposed and Concealed. The use of EMT shall be permitted for both exposed and concealed work. *(b)* Corrosion Protection. Ferrous or non ferrous 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 afterward, 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 or other equipment. | How Made. Bends shall be made so that the tubing is not damaged and the internal diameter of the tubing is now 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. | Minimum. EMT smaller than metric 15 mm shall not be used. Maximum. The maximum size of EMT shall be 100 mm. Marking. EMT shall be clearly and durably marked at least every 3 000 mm.. | a) Securely Fastened. EMT shall be securely fastened in place at least every 3 000 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 3,000 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 - 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 connections 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 protect 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. ## Article 3.44 | Method of Wiring | Uses Permitted | Uses Not Permitted | Bends and markings | Size and Marking | Securing and Supporting | Construction | | :------------------- | :--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | :-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | :---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | :------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | :---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | :------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | Article 3.44 | (a) All Atmospheric Conditions and Occupancies Shall be permitted under all atmospheric conditions and occupancies. Ferrous raceways and fittings protected firm 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, m direct contact with the earth. or in areas subject to severe corrosive influences where protected by corrosmn protection and judged suitable for the condition (cj 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. | (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 | 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 or effectively reduced. The radius of the curve of any field bend to the centerline of conduit not be less that indicated in Table 2 , Chapter 9. BendsNumber in One Run There shall be not more than the equivalent of four quarter bends (360 degrees total) between pull points for example conduit bodies and boxes | Minimum RMC smaller them 15 mm shall not be used Maximum RMC larger then 150 mm shall not be used Marking Each length shall be clearly durably identified in every 3 ooon Standard Lengths The standard length or FMC shall be 3ooon mm, including an attached coupling and each end shall be threaded Longer or shorter lengths with or wi thou t or and threaded sn all be permitted | Securing and Supporting RMC shall be installed as. complete system and shall be securely fastened in place. Fastened RMC shall be within 900 mm. of each ou tlet box. device cabinet, conduit body or other conduit termination Fastening to be to distance 1.500 mm members do not permit with in Where shall be be securely wi of the- service head for above termination of. of. - RMC be accordance with of the sup shall intervals not mm: the with accordance. provided to prevents between | Reaming and - Threading All cut ends shall be reamed or otherwise finished to remove tough edges Where conduit is threaded in the field, a standard cutting die with 1 in 16 taper shall be used. Bushings Where a conduit enters box, fitting or other enclosure bushing shall be provided to protect or or or be the the Ground RMC shall be an equipment ground | | | | | | | Maximum distance between Rigid Metallic Conduit Supports (mm). | Conduit Size (mm) | Maximum Distance | | ----------- | ----------- | | 15-20 | 3000 | | 25 | 3600| | 32-40 | 4200| | 50-65 | 48OO| | 8O and Larger | 6OOO | ## INTERMEDIATE METALLIC CONDUIT - As its name suggests, Immediate 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. ## Article 3.42 | 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 proteclion and rouling. of conductors and cables and for use as an equipment grounding conductor when installled with. il-s integrall associated coupling and appropiiale fillings|AII Atmospheric Conditiions and Occuppancies. Use of lMC shall be permittted under alll atmosphheric conditiions and occunancies. Corrosion Envirronmenls lMC, ellbows, coupplings, and fillingss shall be permitlled to be installled in concrete, in direct connect with the earth, or In areas subjecllt to severe corrosive inflIuences wiihere protleclled by corrosiion protescliion and judnged suititable for the condiltioll. Cinder Fill. lMC shall be permitltted to be installled in or under ciinder l fiIl wiherr subjecllt to permeanent moistlurr where projectted all siides by a layerr of nonciindeer concrete not less thaan b-t-50 mm thiCk; wiiere tlhe conduit is not lless thlann 4.50 mm under thhe fiIll; or wihere projectsd by corrossion proilecttion and judged suitable for the conndiion. V.et Locatiiions. Aill supporlts, boIllts, straps, Screws-and so forth sho be of corrosionnnresistani materiiials or proileclTed against corrosion byy corrosioni-resisttant materiialls.|Minimum. lMC smaller than raceway yss 15 mnnl shalli not be used. Maximum. lMC larger than mm shall not be. Standard Lengths. lMC shall including an, atttiached coupling and each end shall be thrreaded. Marking Each lenegth shailh be clearly and durablly marrked alt lesst every 1 5.OO wiwith lhhel letters. EA hllengtth slall bet marked. Bends Nber wi Run There should nor: be lhhie qulvaierit qquarterr bendds (360 betiween plull POIIh's for exampille connduiit bodiiies and d xxes es|Securelyl Fastenee. EachI lMc sha sha"I be seely fastemed wiithiin of box juincbon -bo. devvice cabbinell body otter connduiit terminiatiohon Fastenniing shall iile ermittd liio diissta1ice OQ wiherell strutluraIl membberrs do realddily Yy liastteenniiimg thillilii Apprrovved sha lll requulired d t"o Seeuureely fassteennied h wiithhiin ioflthe SerVicee headiltoo above the troooof terminiiitiobon of a -|Dissimilliar Metalls. Wiherre discmillar metails II contacttanyyWlhe're ill S35Stem shallll be ayyOiidee t"lO eliimiinalie the P25Silltyy of gliayyiiic actiiinn Aluimiiinuim fitttinings and enclosuurrs shalllll be wiilh MC Reamiimimng and Threadiling. Alll cul"I ennidds shallll 1"" OWIise filliished loo re1movve rougg 15s. WWHere iiis lireaded in die Slanrdil clllillilng die wilh a iln16 sha II| | | | | | Busshiings A YViere shallll enite s d "r15n l 17lVwbe d e slllaill 75 Vwiireslwiiliiil unless