C22.2 No. 244-05 (UL 891) : Switchboards
The Standard applies to switchboards nominally rated at 600 V or less
Last update 05/01/2022
C22.2 No. 244-05 Standard is called a Tristandard because the same content is found in the following three Standards:
- CSA Group: CSA C22.2 No. 244-05
- Underwriters Laboratories Inc: UL 891
- Association of Standardization and Certification: NMX-J-118/2-ANCE-2012
The Standard covers switchboards. The equivalent European standards are EN IEC 61439-1 and EN IEC 61439-2, but the approach is different. EN IEC 61439 puts a lot of emphasis on design verification and testing of the switchgear whereas UL 891 is primarily focused on how to design switchgear.
The Standard applies to switchboards nominally rated up to 600V and intended for use in accordance with the Canadian Electrical Code Part 1 (CE Code, Part 1), the National Electrical Code (NEC), ANSI/NFPA 70, and the Mexican Standard for Electrical Installations (Utility), NOM-001-SEDE.
Moreover, the requirements of the Standard cover switchboards for use on circuits having available rms symmetrical short-circuit currents of not more than 200 000 A.
Table G3.1 is one of the most important tables that switchboards and their bus bars must comply with. The table shows the bus bar width and the minimum distances between bus bars, depending on the minimum and maximum ampere rating and on the maximum voltage rating, with the aim of declaring a maximum rms symmetrical short-circuit current rating.
The bus bars can be arranged "edge to edge" (EE) or "face to face" (FF). The type of arangement chosen affects the minimum permissible distance between the busbars.
Here's a hint: complying with this table requirements means that short-circuit tests may be waived!