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This is the eighth edition of CSA/ANSI Z21.47 • CSA 2.3, Gas-fired central furnaces. It supersedes the previous editions published in 2016, 2012, 2006, 2003, 2001, 1998, and 1993.
The major changes to this edition include the following:
• In Clause 3, the Definitions clause, links have been added to the definition of flue losses. A publication reference has been added to the definition of heat deflection temperature. The definition of heating capacity has been relocated from footnote to Clause 3. The definition for air-intake pipe has been added as recommended by the Z21/83 TC for non-metallic venting. The definition for vent terminal (vent cap) has been deleted. The definition for vent terminal has been revised.
• The clause on direct vent has been relocated from Clause 6.8.5 to Clause 4.2.6 as proposed by the Z21/83 TC for non-metallic venting.
• Clause 4.10.1 has incorporated an interim provision for significant updates to ANSI Z21.20.
• In Clause 4.11.2, existing requirement has been clarified. The current requirements continue only to allow an accessible switch that is integral to the gas control and the only change to the clause is the change from manually to directly for interrupting electric power to automatic valves. For clarification of the intent of the switch, the term manually activated has been proposed to describe the type of switch.
• To accommodate higher discharge air temperatures, Clause 8.7 has been modified for recreational vehicles. If all testing can be passed at the higher temperatures, the restrictions found in the current Clause 4.12.4 for residential style furnaces can safely be eliminated.
• Clause 22.214.171.124, method of test for venting components, has been modified to comply with the Z21/83 TC proposal for non-metallic venting.
• Clause 4.23 on installation manuals has been modified to clarify the conditions under which the furnace must operate when used during the last stages of construction (finishing heat) and prior to occupancy.
• Clarification has been added to Clause 4.23.4 to exclude the use of an external pressure test port.
• In Clause 4.23.6, guidance has been added on testing non-metallic vent pipe without or with thermal insulation, minimum distance from adjacent public walkways, adjacent buildings, openable windows, building openings, protecting building materials from degradation by flue gas, instructions for maximum and minimum vent equivalent length, and instruction to cover building wall penetrations.
• In Clause 5.4 on test gases, an option has been added to conduct burner operating characteristic tests with Test Gas G or H.
• In Clause 126.96.36.199, an option has been added to allow the elbow to be installed inside the enclosure and to allow the use of materials not listed in Table 15 that are tested to ASTM D648. Materials have been removed from Table 15 that are not commonly used.
• In Clause 188.8.131.52, on the method of test for electrical leakage current evaluation, UL 1995 has been replaced with UL 60335-2-40.
• In Clause 5.35.2, on the method of test on venting systems for Category II, III, or IV furnaces, the calculation for allowable leakage rate has been corrected.
• In Clause 6.11.1, on rating plates, an option has been added to list direct or non-direct vent forced air furnace as a configuration.
• Clause 7.4.11, on vent-air intake terminal pendulum load test, has been added based on the Z21/83 TC proposal for non-metallic venting with modifications for furnaces.
• In Clause 8.11.4, on installation marking, the specification for insulation ductwork needed to comply with Clause 9.6 has been added.
• In Clause 13, on items unique to Canada, reference to 3 phase furnaces has been corrected.
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.
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.
In Canada, this Standard applies to gas-fired central furnaces having inputs up to and including 400 000 Btu/h (117 228 W).
This Standard applies to Category I, Category II, Category III, and Category IV central furnaces. See Clause 3.
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.
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).
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.
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.
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.
All references to psi throughout this Standard are considered gauge pressures, unless otherwise specified.
Special construction provisions applicable to a furnace designed for use with an optional listed conversion kit are outlined under Annex H.
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.
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.
Special construction provisions applicable to furnaces designed to operate at altitudes over 2000 ft (610 m) are outlined in Annex K.
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.
Gas-fired central furnaces