CSA - C22.2 NO. 178.1-07
Requirements for transfer switches
|Publication Date:||1 May 2007|
This Standard covers
(a) automatic transfer switches;
(b) manual transfer switches;
(c) closed transition transfer switches;
(d) hybrid transfer switches;
(e) transfer switches for fire pumps; and
(f) bypass/isolating switches
that have a maximum rating of 750 V, are for use in non-hazardous locations in accordance with the Rules of the Canadian Electrical Code, Part I, and enable switching of a power supply from the normal supply to a supply from an alternative source.
Note: Rule 32-206 of the Canadian Electrical Code, Part I, requires that transfer switches for fire pumps be approved for fire pump service.
Transfer switches covered by this Standard may employ solid-state devices only in control circuits and in power circuits of hybrid transfer switches, and only if they are employed for momentary duty and a positive mechanical isolation means is provided.
This Standard does not apply to
(a) double-throw switches covered by CAN/CSA-C22.2 No. 4 for use in optional standby systems;
(b) static switches for uninterruptible power supply systems covered by CSA C22.2 No. 107.1;
(c) switches used in equipment manufactured in accordance with CSA C22.2 No. 141;
(d) manually operated generator transfer panels covered by CSA C22.2 No. 178.2; and
(e) high-voltage automatic transfer switches covered by CSA C22.2 No. 178.3.
In CSA Standards, "shall" is used to express a requirement, i.e., a provision that the user is obliged to satisfy in order to comply with the standard; "should" is used to express a recommendation or that which is advised but not required; "may" is used to express an option or that which is permissible within the limits of the standard; and "can" is used to express possibility or capability. Notes accompanying clauses do not include requirements or alternative requirements; the purpose of a note accompanying a clause is to separate from the text explanatory or informative material. Notes to tables and figures are considered part of the table or figure and may be written as requirements. Legends to equations and figures are considered requirements. Annexes are designated normative (mandatory) or informative (non-mandatory) to define their application.