CSA/ANSI Z21.47:21 • CSA 2.3:21

1 Scope 1.1 This Standard applies to automatically operating gas-fired central furnaces (see Clause 3), hereinafter referred to as furnaces, for installation in residential, commercial, and industrial structures including furnaces for direct vent, recreational vehicle, outdoor, and manufactured (mobile) homes. These furnaces can include a cooling unit. All units are to be constructed entirely of new, unused parts and materials. 1.2 In Canada, this Standard applies to gas-fired central furnaces having inputs up to and including 400 000 Btu/h (117 228 W). 1.3 This Standard applies to Category I, Category II, Category III, and Category IV central furnaces. See Clause 3. 1.4 This Standard applies to furnaces of the types defined in Clause 3, which are designed to supply heated air through ducts to spaces remote from or adjacent to the furnace location. Location and use of such furnaces with respect to the spaces being heated necessitates automatic operation of the appliance. 1.5 This Standard covers the thermal efficiency (see Clause 5.40) and related markings of only those furnaces whose efficiencies are not regulated in the U.S.A. by the Energy Policy Act and Conservation Act of 1975 and the National Energy Conservation Policy of 1978* or not covered in Canada by Clause 13 when connected to a single phase electrical supply. Note: * At the time of printing, Federal energy acts in the U.S.A. regulate the efficiency (heating capacity) of furnaces having input ratings less than 225 000 Btu/h (65 941 W). 1.6 A furnace of a type not specifically defined in this Standard may be subjected to such examination and tests as deemed necessary by the testing agency to determine compliance with the intent of this Standard. 1.7 This Standard also applies to a furnace that is factory equipped with both a draft hood and an automatic vent damper device (see Clause 3), hereinafter referred to as vent damper device. 1.8 If a value for measurement as given in this Standard is followed by an equivalent value in other units, the first stated value is regarded as the specification, except as noted in Clauses 4.22.1 and 4.26.2. 1.9 All references to “psi” throughout this Standard are considered gauge pressures, unless otherwise specified. 1.10 Special construction provisions applicable to a furnace designed for use with an optional listed conversion kit are outlined under Annex H. 1.11 Clause 2 contains a list of standards specifically referenced in this Standard. Clause 2 includes both U.S. and Canadian reference standards where applicable. It is the responsibility of the user of this Standard to determine which referenced standard applies based on the requirements of the authority having jurisdiction at the location of the installation. However, a furnace for use in a particular country only should comply with the applicable referenced standard for that country. 1.12 Clause 4.17 is unique to United States. The Canadian electrical equipment and wiring provisions are contained in CSA C22.2 No. 3 or CAN/CSA-C22.2 No. 60335-2-102. 1.13 Special construction provisions applicable to furnaces designed to operate at altitudes over 2000 ft (610 m) are outlined in Annex K. 1.14 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.