---
id:
aliases:
  - nec-310
tags:
  - authorship/other
  - destiny/uncertain
  - status/incomplete
  - topic/construction/electrical
  - type/media
  - exclude-from-word-count
title:
---
# Article 300: General Requirements for Wiring Methods and Materials

## Part I. General Requirements

### 300.1 Scope.

#### 300.1(A) All Wiring Installations.

This article covers general requirements for wiring methods and materials for all wiring installations unless modified by other articles in Chapter 3.

#### 300.1(B) Integral Parts of Equipment.

The provisions of this article are not intended to apply to the conductors that form an integral part of equipment, such as motors, controllers, motor control centers, or factory-assembled control equipment or listed utilization equipment.

#### 300.1(C) Metric Designators and Trade Sizes.

Metric designators and trade sizes for conduit, tubing, and associated fittings and accessories shall be as designated in Table 300.1(C).

#### Table 300.1(C) Metric Designators and Trade Sizes

| Metric Designator | Trade Size |
| -----------------:| ----------:|
|                12 |        3/8 |
|                16 |        1/2 |
|                21 |        3/4 |
|                27 |          1 |
|                35 |      1-1/4 |
|                41 |      1-1/2 |
|                53 |          2 |
|                63 |      2-1/2 |
|                78 |          3 |
|                91 |      3-1/2 |
|               103 |          4 |
|               129 |          5 |
|               155 |          6 |

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### 300.19 Supporting Conductors in Vertical Raceways.

#### 300.19(A) Spacing Intervals -- Maximum.

Conductors in vertical raceways shall be supported
if the vertical rise exceeds the values in Table 300.19(A).
At least one support method shall be provided for each conductor
at the top of the vertical raceway or as close to the top as practical.
Intermediate supports shall be provided
as necessary to limit supported conductor lengths
to not greater than those values specified in Table 300.19(A).

#### Table 300.19(A) Spacings for Conductor Supports

| Conductor Size                   | Aluminum or Copper-Clad Aluminum | Copper |
| -------------------------------- | --------------------------------:| ------:|
| 18 AWG through 8 AWG             |                            100ft |  100ft |
| 6 AWG through 1/0 AWG            |                            200ft |  100ft |
| 2/0 AWG through 4/0 AWG          |                            180ft |   80ft |
| Over 4/0 AWG through 350 kcmil   |                            135ft |   60ft |
| Over 350 kcmil through 500 kcmil |                            120ft |   50ft |
| Over 500 kcmil through 750 kcmil |                             95ft |   40ft |
| Over 750 kcmil                   |                             85ft |   35ft |

#### 300.19(B) Fire-Rated Cables and Conductors.

Support methods and spacing intervals for fire-rated cables and conductors
shall comply with any restrictions provided in the listing
of the electrical circuit protective system used
and in no case shall exceed the values in Table 300.19(A).

#### 300.19(C) Support Methods.

One of the following methods of support shall be used:

1. Clamping devices constructed of or employing insulating wedges
  inserted in the ends of the raceways.
  Where clamping of insulation does not adequately support the cable,
  the conductor also shall be clamped.

2. Inserting boxes at the required intervals
  in which insulating supports are installed and secured
  in an approved manner to withstand the weight of the conductors attached thereto,
  the boxes being provided with covers.

3. In junction boxes, deflecting the cables not less than 90 degrees
  and carrying them horizontally to a distance not less than twice the diameter of the cable,
  the cables being carried on two or more insulating supports
  and additionally secured thereto by tie wires, if desired.
  Where this method is used, cables shall be supported at intervals
  not greater than 20 percent of the support spacing in Table 300.19(A).

4. Other approved means.

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