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Cablebus

Posted By Steve Douglas, Tuesday, January 01, 2013
Updated: Friday, December 14, 2012

The new standard for cablebus C22.2 No 273 is scheduled for publication by September of this year. This new standard will be the first standard for cablebus in North America. The committee includes the six major cablebus manufacturers in North America, two switchgear manufacturers, CSA, and an IAEI representative. 

Cablebus is an assembly

Cablebus is an assembly of insulated conductors with fittings and conductor terminations in a completely enclosed, ventilated, or non-ventilated protective metal housing. In most cases, cablebus will be approved by either certification or field evaluation and is typically assembled at the point of installation from the components furnished by the cablebus manufacturer. Accompanying the cablebus, the manufacturer will provide installation instructions and drawings for the specific installation to facilitate:

a) system design;

b) construction;

c) fire stop rating (where applicable);

d) weatherproof entrance fittings (where appli-cable);

e) bonding, conductor and shield terminations (where applicable);

f) grounding of shields (where applicable) and installation;

g) inclusion of electrical detail of the conductor configuration, together with enclosure dimensions;

h) specification of maximum allowable span support; and

i) vertical installations.

Cablebus nameplate

To assist the electrical contractor and electrical inspector the main nameplate will include:

a)   The manufacturer’s name, trademark, or other descriptive marking by which the organization responsible for the product can be identified;

b)   The electrical ratings:

– rated nominal voltage, (Vrms or Vdc)

– frequency in Hz

– allowable ampacity  (Amps),  based on ambient temperature* of XX*C, and based on a maximum operating temperature of XX*C- short circuit current rating  

– number of phases (poles for dc);

– 3-wire or 4-wire; and

–Maximum continuous current rating _XX_A, when connected to a 100% continuous rated overcurrent device

– Maximum continuous current rating _XX_A, when connected to a 80% continuous rated overcurrent device

*Note: the temperature is the maximum ambient temperature that the equipment was designed to operate in.

c) The month and year of manufacture, at least, shall be marked on the cablebus system in a location accessible without the use of tools.

d)   The number of conductors and size per phase.

e) As a minimum, the allowable ampacity (amps) based on a maximum operating temperature of 75°C  shall be included on the nameplate.

f) Type of material, such as stainless steel (including the type), aluminum, etc., and, if carbon steel, Type 1 (hot-dip galvanized), Type 2 (mill galvanized), or Type 3 (electrodeposited zinc), as applicable. If the manufacturer’s catalogue number marked on the product would readily lead the user to the required information published by the manufacturer, this marking is not mandatory;

g) a warning label that reads, "WARNING! DO NOT USE AS A WALKWAY, LADDER, OR SUPPORT FOR PERSONNEL; and

h) the design drawing number for the specific installation.

Maximum continuous current rating

The maximum continuous current rating will assist in the application of CE Code Rules 12-2260 and 8-104 and help provide consistency with respect to conductor loading. In addition to these nameplate markings, cablebus will be one of two classes corresponding with the Items (a) and (b) in CE Code Rule 12-2252. CE Code Part I Rule 12-2252 states:

12-2252 Use of cablebus (see Appendix B)

Cablebus shall be permitted for use where

(a) protection from contact with conductors is provided by design and construction of the enclosure; or

(b) installation is intended in areas

(i) accessible only to authorized persons;

(ii) isolated by elevation or by barriers; and

(iii) where qualified electrical maintenance personnel service the installation.

Class A cablebus is designed with protection from conductors contact provided by the design and construction of the enclosure. Class B cablebus is intended to be installed in areas accessible to authorized persons, isolated by elevation or by barriers, and where qualified electrical maintenance personnel service the installation.


Steve Douglas is presently the senior technical codes specialist for QPS Evaluation Services. As the International Association of Electrical Inspectors representative on Part I and Part II of the Canadian Electrical Code, Steve is the vice chair of the CE Code Part I, chair of CE Code Part I Subcommittees for Section 2, 12, and 50, and a member on Sections 40, 64, 68, 76 and Appendix D. In addition, Steve is the chair of the CSA Standards C22.2 No. 273 Cablebus, C22.6 No. 1, Electrical Inspection Code for Existing Residential Occupancies committee; the chair of the SPE-1000 Working Group; and a member on committees for the Objective Based Industrial Electrical Code, Safety Management Systems, Solar Photovoltaic Modules, Photovoltaic Cable, Fuel Cells, Wind Turbines, Distribution transformers, Outlet Boxes, and Wiring Fittings Hardware and Positioning Devices. 

Tags:  Featured  January-February 2013 

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