CSA/ANSI Z21.78:25/CSA 6.20:25

Preface This is the fifth edition of CSA/ANSI Z21.78 • CSA 6.20, Combination gas controls for gas appliances. It supersedes the previous editions published in 2010, 2005, 2000, and 1997. The major changes to this edition include the following: a) the scope (Clause 1) has been updated to include propane, hydrogen, and hydrogen admixtures and to remove manufactured, mixed, and LP gases; b) Clause 5.2.4 has been revised; c) Clause 5.9.3 has been revised; d) Clause 5.9.4 has been revised; e) Clause 5.9.6.2 has been updated to include hydrogen and hydrogen admixtures; f) Table 11 has been updated to include hydrogen and hydrogen admixtures; g) Clause 5.10.3 has been revised; h) Table 13 has been added; and i) Clause 5.10.4 has been revised. This Standard is considered suitable for use for conformity assessment within the stated scope of the Standard. This Standard was prepared by the Z21/CSA Joint Subcommittee on Automatic Gas Controls, under the jurisdiction of the Technical Committee on Gas Appliances and Related Accessories and the Strategic Steering Committee on Fuels and Appliances, and has been formally approved by the Technical Committee. This Standard has been developed in compliance with Standards Council of Canada requirements for National Standards of Canada. It has been published as a National Standard of Canada by CSA Group. This Standard has been approved by the American National Standards Institute (ANSI) as an American National Standard. Scope 1.1 Inclusions This Standard applies to newly produced combination gas controls, hereinafter referred to as controls, constructed entirely of new, unused parts and materials. 1.2 Additional inclusions The combination control may include other functions such as pilot gas filters, pressure switches, etc., of an approved type or be investigated as an integral part of the combination control for construction and performance equivalent to an approved type. A control which incorporates two or more automatic valves and no other function (as defined by combination control) may be tested to CSA/ANSI Z21.21 • CSA 6.5 at the discretion of the manufacturer. 1.3 Exclusions Compliance of a combination control with this Standard does not imply that the combination control is acceptable for use on gas appliances without supplemental tests with the combination control applied to the particular appliance design. 1.4 Pressure ratings This Standard applies to combination controls having a maximum operating gas pressure of 1/2 psi (3.5 kPa) with one or more of the following fuel gases: natural, propane, hydrogen, and hydrogen gas admixtures. 1.5 Temperature ratings This Standard applies to combination controls which are capable of operation in ambient temperatures of 32 °F (0 °C) to 125 °F (51.5 °C), unless a higher temperature, lower temperature, or both, are specified by the manufacturer. 1.6 Additional provisions for the United States Clause 6contains items unique to the United States. 1.7 Additional provisions for Canada Clause 7 contains items unique to Canada. 1.8 Pressure references All references to pounds per square inch (psi) in this Standard are considered gauge pressure unless otherwise specified. 1.9 Terminology 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. 1.10 Units of measurement The values given in US customary units are the units of record for the purposes of this Standard. The values given in parentheses are for information and comparison only.