This is the third edition of C22.2 No. 177, Clock-operated switches. It supersedes the previous editions published in 1992 and 1981. It is one of a series of Standards issued by CSA Group under Part II of the Canadian Electrical Code.
This Standard applies to clock-operated switches, rated 600 V or less, designed to be used in ordinary locations to close and open circuits to a load at predetermined intervals, and intended to be employed in accordance with the Rules of the Canadian Electrical Code, Part I. The clock-operated switches discussed in this Standard may be
a) completely enclosed, plug-in, or cord-connected;
b) incomplete in their enclosure or in other constructional features; or
c) restricted in performance capabilities for use in other equipment.
Note: The word switch, when used without further qualification in subsequent Clauses of this Standard, denotes a clock-operated switch.
This Standard applies to clock-operated switches in which the switching contacts are actuated by a clock-work, a gear-train, hand, electrically-wound spring motors, electric clock-type motors, electronic circuits, or equivalent arrangements. In addition to closing and/or opening the switching contacts, the clock-operated switches may also indicate the time of day or time interval. This Standard also applies to TV-rated clock-operated switches.
General requirements applicable to this Standard are given in CAN/CSA-C22.2 No. 0.
In this Standard, 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; and may is used to express an option or that which is permissible within the limits of the Standard.
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.
Annexes are designated normative (mandatory) or informative (non-mandatory) to define their application.