ANSI Z21.13-2017 • CSA 4.9-2017

This Standard applies to newly produced gas-fired low-pressure steam and hot water boilers with gas inlet pressure ratings not exceeding 0.5 psi (3.5 kPa) and having input ratings of less than 12,500,000 Btu/hr (3 663 389 W) (see Clause 3, Definitions), hereinafter referred to as boilers*, constructed entirely of new unused parts and materials, for operation at or below the following pressures and temperatures: Steam heating boilers 15 psi (103.42 kPa) steam pressure Hot water heating boilers 160 psi (1.10 MPa) water pressure 250 °F (121 °C) water temperature Hot water supply boilers 160 psi (1.10 MPa) water pressure 250 °F (121 °C) water temperature a) for use with natural gas; b) for use with manufactured gas; c) for use with mixed gas; d) for use with liquefied petroleum gases; and e) for use with LP gas-air mixtures. The construction of boilers for use with the above-mentioned gases is covered under Clause 4, Construction. The performance of boilers for use with the above-mentioned gases is covered under Clause 5, Performance. * See Clause 7.2, Scope for boilers covered in Canada that exceed the above limits in gas inlet pressure and/or input ratings. 1.2 This Standard applies to indoor boilers, of other than the direct vent type which are categorized according to vent pressure and temperature as either Category I, Category II, Category III or Category IV (see Clause 3, Definitions), and to outdoor type boilers. 1.3 This Standard also applies to direct vent boilers (see Clause 3, Definitions). A direct vent boiler anticipated by this Standard is essentially a balanced flue appliance with the air intake and vent outlet in proximity. Other designs are subjected to such additional tests as believed necessary at the discretion of the testing agency. 1.4 See Clause 7, Items unique to Canada, for the Canadian Method of Test to determine combustion efficiency for indoor boilers and the thermal efficiency for both indoor and outdoor boilers. 1.5 If a value for measurement as given in this Standard is followed by an equivalent value in other units, the first stated value is to be regarded as the specification. 1.6 This Standard contains SI (Metric) corresponding to the yard/pound quantities, the purpose being to allow the Standard to be used in SI (Metric) units. (Standard for Use of the International System of Units (SI): The Modern Metric System, IEEE/ASTM SI 10 or ISO 80000-1:2009 Quantities and units – Part 1: General are used as a guide in making metric conversion from yard/pound quantities.) If a value for a measurement and a corresponding value in other units is stated, the first stated value is to be regarded as the requirement. The given corresponding value may be approximate. If a value for a measurement and corresponding value in other units are both specified as a quoted marking requirement, the first stated unit, or both shall be provided. 1.7 All references to pressure throughout this Standard are to be considered gauge pressure, unless otherwise specified. 1.8 Clause 7, Items unique to Canada, contains clauses unique to, and required by, Canada. 1.9 In this Standard, “shall” is used to express a requirement, i.e., a provision that the user shall 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.