Shop Practice with Electrical Code: Wiring Materials Jayson Bryan E. Mutuc, REE, RME BSEE-PUP MSEE, Major in Power Systems -MIT (candidate)
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Chapter 3 Wiring Methods and Materials Article 3.42 INTERMEDIATE METAL CONDUIT: Type IMC Intermediate metal conduit (IMC) is a steel tubing heavier than EMT but lighter than RMC. It may be threaded. 3.42.2.11 Size (a) Minimum. IMC smaller than raceway size 15 mm shall not be used. (b) Maximum. IMC larger than raceway size 100 mm shall not be used 3.42.3.1 Marking Each length shall be clearly and durably marked at least every 1500 mm with the letters IMC. Each length shall be marked as required in 1.10.1.21
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Chapter 3 Wiring Methods and Materials Article 3.44 RIGID METAL CONDUIT: RMC is generally made of steel (ferrous) with protective coatings or aluminum (non ferrous). Special use types are silicon bronze and stainless steel 3.44.2.11 Size (a) Minimum. RMC smaller than raceway size 15 mm shall not be used. (b) Maximum. RMC larger than raceway size 150 mm shall not be used 3.44.3.1 Marking Each length shall be clearly and durably marked at least every 3000 mm as required in the first sentence of 1.10.1.21. Non ferrous conduit of corrosion-resistant material shall have suitable markings
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Chapter 3 Wiring Methods and Materials Article 3.52 RIGID NONMETALLIC CONDUIT: Rigid nonmetallic conduit (RNC) is a non-metallic unthreaded smooth-walled tubing. 3.52.2.11 Size (a) Minimum. RNC smaller than raceway size 15 mm shall not be used. (b) Maximum. RNC larger than raceway size 150 mm shall not be used 3.52.3.21 Marking Each length of RNC shall be clearly and durably marked at least every 3000 mm as required in the first sentence of 1.10.1.21.
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Chapter 3 Wiring Methods and Materials Article 3.58 ELECTRICAL METALLIC TUBING An unthreaded thinwall raceway of circular cross section. EMT is generally made of steel (ferrous) with protective coatings or aluminum (nonferrous) 3.58.2.11 Size (a) Minimum. EMT smaller than raceway size 15 mm shall not be used. (b) Maximum. EMT larger than raceway size 100 mm shall not be used 3.58.3.21 Marking EMT shall be clearly and durably marked at least every 3000 mm as required in the first sentence of 1.10.1.21.
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Chapter 3 Wiring Methods and Materials Article 3.62 ELECTRICAL NONMETALLIC TUBING A nonmetallic pliable corrugated raceway of circular cross section. ENT is composed of material that is Resistant to moisture and chemical atmosphere and is flame retardant 3.62.2.11 Size (a) Minimum. ENT smaller than raceway size 15 mm shall not be used. (b) Maximum. ENT larger than raceway size 50 mm shall not be used 3.62.3.21 Marking ENT shall be clearly and durably marked at least every 3000 mm as required in the first sentence of 1.10.1.21.
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Same Provisions Same Provisions of IMC, RMC, RNC, EMT, ENT
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.
Bushings (IMC, RMC, RNC, ENT). Where a conduit eneters a box, fitting, or other enclosure, a bushing shall be provided to protect the wire from abrasion unless the design of the box, fitting enclosure is afford equivalent protection.
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Same Provisions Securing and Supporting. IMC, RMC, RNC, EMT, ENT shall be securely fastened within 900 mm of each outlet box, junction box, device box, conduit body, or other conduit termination. For IMC and RMC fastening shall be permitted to be increased to a distance of 1500 mm where structural members do not readily permit fastening within 900 mm
EMT and IMC support intervals
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Same Provisions 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
Table 3.52.2.21 (b) Supports for Rigid Nonmetallic Conduit (RNC) Conduit Size (mm)
Maximum Spacing Between Supports (mm)
15-25
900
32-50
1500
4200
65-80
1800
50-65
4800
90-125
2100
80 and larger
6000
150
2400
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Auxiliary Gutter and Wireways Article 3.66 Auxiliary Gutter Metallic Auxiliary Gutter. Sheet of metal enclosure with hinged or removable covers for housing and protecting electrical wires, cable, and busbars which conductors are laid in place after the wireway has been installed as a complete system. Nonmetallic Auxiliary Gutters. Flame retardant, non metallic enclosures.
Article 3.76 Metal Wireways Metal Wireways. Sheet of metal troughs with hinged or removable covers for housing and proctecting electric wires and cable and in which conductor are laid in place after the wireway has been installed as a complete system. Nonmetallic Wireways. Flame retardant, nonmetallic trough
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Auxiliary Gutter and Wireways Number of Conductors. The sum of cross-sectional areas of all contained conductors at any cross section of the gutter or wireway shall not exceed 20 percent of the interior crosssectional area of the gutter or wireway
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