Surge protective devices - Type 4 - Component assemblies

1.1
This Standard covers component assembly surge protective devices (SPDs) consisting of two or more Type 5 components, intended for use in Type 1, 2, or 3 SPD applications. 

1.2
Type 4 component assemblies are designed for repeated limiting of transient voltage surges as specified in this Standard on 50 or 60 Hz power circuits over 42 V and not exceeding 750 V. 

1.3
The surge protective component used in a Type 4 component assembly may include but not be limited to metal oxide varistors (MOVs), silicon avalanche diodes (SADs), spark gaps, and gas discharge tubes (GDT).

1.4
This Standard does not apply to EMI filters which may have surge suppression characteristics as covered in CSA C22.2 No. 8. 

1.5
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 (nonmandatory) to define their application.