---
aliases:
  - nec-370
title: Article 370 Cablebus
tags:
  - authorship/other
  - exclude-from-word-count
  - topic/construction/electrical
  - type/media/reference
---
# Article 370 Cablebus

## Part I. General

### 370.1 Scope.

This article covers the use and installation requirements of cablebus and associated fittings.

### 370.2 Definition.

The definition in this section shall apply within this article and throughout the Code.

#### Cablebus.

An assembly of units or sections with insulated conductors having associated fittings forming a structural system used to securely fasten or support conductors and conductor terminations in a completely enclosed, ventilated, protective metal housing. This assembly is designed to carry fault current and to withstand the magnetic forces of such current.

> [!info] Informational Note:
> Cablebus is ordinarily assembled at the point of installation from the components furnished or specified by the manufacturer in accordance with instructions for the specific job.

## Part II. Installation

### 370.10 Uses Permitted.

Approved cablebus shall be permitted:

* (1) At any voltage or current for which spaced conductors are rated and where installed only for exposed work, except as permitted in 370.18

* (2) For branch circuits, feeders, and services

* (3) To be installed outdoors or in corrosive, wet, or damp locations where identified for the use

### 370.12 Uses Not Permitted.

Cablebus shall not be permitted to be installed in the following:

* (1) Hoistways

* (2) Hazardous (classified) locations, unless specifically permitted in Chapter 5

### 370.18 Cablebus Installation.

#### 370.18(A) Transversely Routed.

Cablebus shall be permitted to extend transversely through partitions or walls, other than fire walls, provided that the section within the wall is continuous, protected against physical damage, and unventilated.

#### 370.18(B) Through Dry Floors and Platforms.

Except where firestops are required, cablebus shall be permitted to extend vertically through dry floors and platforms, provided that the cablebus is totally enclosed at the point where it passes through the floor or platform and for a distance of 1.8 m (6 ft) above the floor or platform.

#### 370.18(C) Through Floors and Platforms in Wet Locations.

Except where firestops are required, cablebus shall be permitted to extend vertically through floors and platforms in wet locations where:

* (1) There are curbs or other suitable means to prevent waterflow through the floor or platform opening, and

* (2) Where the cablebus is totally enclosed at the point where it passes through the floor or platform and for a distance of 1.8 m (6 ft) above the floor or platform.

### 370.20 Conductor Size and Termination.

#### 370.20(A) Conductors.

The current-carrying conductors in cablebus shall:

* (1) Have an insulation rating of 75°C (167°F) or higher and be of an approved type suitable for the application.

* (2) Be sized in accordance with the design of the cablebus but in no case be smaller than 1/0.

#### 370.20(B) Termination.

Approved terminating means shall be used for connections to cablebus conductors.

> [!info] Informational Note No. 1:
> See 110.14(C) for conductor temperature limitations due to termination provisions for installations up to and including 2000 volts.

> [!info] Informational Note No. 2:
> See 110.40 for conductor temperature limitations due to termination provisions for installations 2001 volts to
35,000 volts.

### 370.22 Number of Conductors.

The number of conductors shall be that for which the cablebus is designed.

### 370.23 Overcurrent Protection.

Cablebus shall be protected against overcurrent in accordance with the ampacity of the cablebus conductors in accordance with 240.4.

> [!important] Exception:
> Overcurrent protection shall be permitted in accordance with 240.100 and 240.101.

### 370.30 Securing and Supporting.

#### 370.30(A) Cablebus Supports.

Cablebus shall be securely supported at intervals not exceeding 3.7 m (12 ft). Where spans longer than 3.7 m (12 ft) are required, the structure shall be specifically designed for the required span length.

#### 370.30(B) Conductor Supports.

The insulated conductors shall be supported on blocks or other identified mounting means.

The individual conductors in a cablebus shall be supported at intervals not greater than 900 mm (3 ft) for horizontal runs and 450 mm
(1 1/2 ft) for vertical runs. Vertical and horizontal spacing between supported conductors shall be not less than one conductor diameter at the points of support.

### 370.42 Fittings.

A cablebus system shall include approved fittings for the following:

* (1) Changes in horizontal or vertical direction of the run

* (2) Dead ends

* (3) Terminations in or on connected apparatus or equipment or the enclosures for such equipment

* (4) Additional physical protection where required, such as guards where subject to severe physical damage

### 370.60 Grounding.

A cablebus system shall be grounded and/or bonded as applicable:

* (1) Cablebus framework, where bonded, shall be permitted to be used as the equipment grounding conductor for branch circuits and feeders.

* (2) A cablebus installation shall be grounded and bonded in accordance with Article 250, excluding 250.86, Exception No. 2.

### 370.80 Ampacity of Conductors.

The ampacity of conductors in cablebus shall be in accordance with 310.17 and 310.19 for installations up to and including 2000 volts, or with Table 311.60(C)(69) and Table 311.60(C)(70) for installations 2001 volts to 35,000 volts.

## Part III. Construction Specifications

### 370.120 Marking.

Each section of cablebus shall be marked with the manufacturer's name or trade designation and the maximum diameter, number, voltage rating, and ampacity of the conductors to be installed. Markings shall be located so as to be visible after installation.
