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vault backup: 2026-01-23 15:26:10

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Zane Meyers
2026-01-23 15:26:10 -05:00
parent 1e0a853527
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nfpa-70_300_general-requirements.md
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@@ -332,7 +332,7 @@ Under minimum of 102 mm
Under streets, highways, roads, alleys, driveways, and parking lots
600 24 600 24 600 24 600 24 600 24
One- and two-family dwelling driveways and outdoor parking areas, and used only for dwellingrelated purposes
One- and two-family dwelling driveways and outdoor parking areas, and used only for dwelling-related purposes
450 18 450 18 450 18 300 12 450 18
In or under airport runways, including adjacent areas where trespassing prohibited
@@ -660,11 +660,33 @@ A bushing shall be permitted in lieu of a box or terminal where the conductors e
The number and size of conductors in any raceway shall not be more than will permit dissipation of the heat and ready installation or withdrawal of the conductors without damage to the conductors or to their insulation.
> [!info] Informational Note:
> See the following sections of this Code: intermediate metal conduit, 342.22; rigid metal conduit, 344.22; flexible metal conduit, 348.22; liquidtight flexible metal conduit, 350.22; PVC conduit, 352.22; HDPE conduit, 353.22; RTRC, 355.22; liquidtight nonmetallic flexible conduit, 356.22; electrical metallic tubing, 358.22; flexible metallic tubing, 360.22; electrical nonmetallic tubing,
362.22; cellular concrete floor raceways, 372.22; cellular metal floor raceways, 374.22; metal wireways, 376.22; nonmetallic wireways,
378.22; surface metal raceways, 386.22; surface nonmetallic raceways, 388.22; underfloor raceways, 390.22; fixture wire, 402.7; theaters, 520.6; signs, 600.31(C); elevators, 620.33; audio signal processing, amplification, and reproduction equipment, 640.23(A) and
640.24; Class 1, Class 2, and Class 3 circuits, Article 725; fire alarm circuits, Article 760; and optical fiber cables and raceways, Article
770.
> See the following sections of this Code:
> intermediate metal conduit, 342.22;
> rigid metal conduit, 344.22;
> flexible metal conduit, 348.22;
> liquidtight flexible metal conduit, 350.22;
> PVC conduit, 352.22;
> HDPE conduit, 353.22;
> RTRC, 355.22;
> liquidtight nonmetallic flexible conduit, 356.22;
> electrical metallic tubing, 358.22;
> flexible metallic tubing, 360.22;
> electrical nonmetallic tubing, 362.22;
> cellular concrete floor raceways, 372.22;
> cellular metal floor raceways, 374.22;
> metal wireways, 376.22;
> nonmetallic wireways, 378.22;
> surface metal raceways, 386.22;
> surface nonmetallic raceways, 388.22;
> underfloor raceways, 390.22;
> fixture wire, 402.7;
> theaters, 520.6;
> signs, 600.31(C);
> elevators, 620.33;
> audio signal processing, amplification, and reproduction equipment, 640.23(A) and 640.24;
> Class 1, Class 2, and Class 3 circuits, Article 725;
> fire alarm circuits, Article 760;
> and optical fiber cables and raceways, Article 770.
### 300.18 Raceway Installations.
@@ -763,8 +785,7 @@ Where a single conductor carrying alternating current passes through metal with
Electrical installations in hollow spaces, vertical shafts, and ventilation or air-handling ducts shall be made so that the possible spread of fire or products of combustion will not be substantially increased. Openings around electrical penetrations into or through fireresistant-rated walls, partitions, floors, or ceilings shall be firestopped using approved methods to maintain the fire resistance rating.
> [!info] Informational Note:
> Directories of electrical construction materials published by qualified testing laboratories contain many listing installation restrictions necessary to maintain the fire-resistive rating of assemblies where penetrations or openings are made. Building codes also contain restrictions on membrane penetrations on opposite sides of a fire-resistance-rated wall assembly. An example is the
600-mm (24-in.) minimum horizontal separation that usually applies between boxes installed on opposite sides of the wall. Assistance in complying with 300.21 can be found in building codes, fire resistance directories, and product listings.
> Directories of electrical construction materials published by qualified testing laboratories contain many listing installation restrictions necessary to maintain the fire-resistive rating of assemblies where penetrations or openings are made. Building codes also contain restrictions on membrane penetrations on opposite sides of a fire-resistance-rated wall assembly. An example is the 600-mm (24-in.) minimum horizontal separation that usually applies between boxes installed on opposite sides of the wall. Assistance in complying with 300.21 can be found in building codes, fire resistance directories, and product listings.
### 300.22 Wiring in Ducts Not Used for Air Handling, Fabricated Ducts for Environmental Air, and Other Spaces for Environmental Air (Plenums).
@@ -829,9 +850,7 @@ The provisions in 300.22(C)(2)(a) or (C)(2)(b) shall apply to the use of metalli
Electrical equipment with a metal enclosure, or electrical equipment with a nonmetallic enclosure listed for use within an air-handling space and having low smoke and heat release properties, and associated wiring material suitable for the ambient temperature shall be permitted to be installed in such other space unless prohibited elsewhere in this Code.
> [!info] Informational Note:
> One method to determine low smoke and heat release properties is that the equipment exhibits a maximum peak optical density of 0.50 or less, an average optical density of 0.15 or less, and a peak heat release rate of 100 kW or less when tested in accordance with ANSI/UL 2043-2013, Fire Test for Heat and Visible Smoke Release for Discrete Products and Their Accessories
Installed in Air-Handling Spaces.
> One method to determine low smoke and heat release properties is that the equipment exhibits a maximum peak optical density of 0.50 or less, an average optical density of 0.15 or less, and a peak heat release rate of 100 kW or less when tested in accordance with ANSI/UL 2043-2013, Fire Test for Heat and Visible Smoke Release for Discrete Products and Their Accessories Installed in Air-Handling Spaces.
> [!important] Exception:
> Integral fan systems shall be permitted where specifically identified for use within an air-handling space.
@@ -863,8 +882,7 @@ See [[#300.3(C)(2) Over 1000 Volts, Nominal.|300.3(C)(2)]].
### 300.34 Conductor Bending Radius.
The conductor shall not be bent to a radius less than 8 times the overall diameter for nonshielded conductors or 12 times the overall diameter for shielded or lead-covered conductors during or after installation. For multiconductor or multiplexed single-conductor cables having individually shielded conductors, the minimum bending radius is 12 times the diameter of the individually shielded conductors or
7 times the overall diameter, whichever is greater.
The conductor shall not be bent to a radius less than 8 times the overall diameter for nonshielded conductors or 12 times the overall diameter for shielded or lead-covered conductors during or after installation. For multiconductor or multiplexed single-conductor cables having individually shielded conductors, the minimum bending radius is 12 times the diameter of the individually shielded conductors or 7 times the overall diameter, whichever is greater.
### 300.35 Protection Against Induction Heating.
@@ -1072,9 +1090,7 @@ The interior of enclosures or raceways installed underground shall be considered
#### 300.50(C) Protection from Damage.
Conductors emerging from the ground shall be enclosed in listed raceways. Raceways installed on poles shall be of rigid metal conduit, intermediate metal conduit, RTRC-XW, Schedule 80 PVC conduit, or equivalent, extending from the minimum cover depth specified in
Table 300.50 to a point 2.5 m (8 ft) above finished grade. Conductors entering a building shall be protected by an approved enclosure or raceway from the minimum cover depth to the point of entrance. Where direct-buried conductors, raceways, or cables are subject to movement by settlement or frost, they shall be installed to prevent damage to the enclosed conductors or to the equipment connected to the raceways. Metallic enclosures shall be grounded.
Conductors emerging from the ground shall be enclosed in listed raceways. Raceways installed on poles shall be of rigid metal conduit, intermediate metal conduit, RTRC-XW, Schedule 80 PVC conduit, or equivalent, extending from the minimum cover depth specified in Table 300.50 to a point 2.5 m (8 ft) above finished grade. Conductors entering a building shall be protected by an approved enclosure or raceway from the minimum cover depth to the point of entrance. Where direct-buried conductors, raceways, or cables are subject to movement by settlement or frost, they shall be installed to prevent damage to the enclosed conductors or to the equipment connected to the raceways. Metallic enclosures shall be grounded.
#### 300.50(D) Splices.