Preface This is the second edition of CSA P.7, Test method for measuring energy loss of gas-fired instantaneous water heaters. It supersedes the previous edition, published in 1998 under the title Testing Method for Measuring Energy Loss of Gas-Fired Instantaneous Water Heaters. Scope 1.1 This Standard specifies procedures for 24 h simulated-use testing of gas-fired instantaneous water heaters. This Standard also provides calculations for the determination of (a) the maximum L/min (gpm) rating; (b) recovery efficiency (thermal efficiency); (c) daily water-heating energy consumption; (d) energy factor; and (e) annual energy consumption. 1.2 This Standard applies to gas-fired instantaneous water heaters that (a) initiate heating based on water flow; (b) use a fixed or variable input; (c) have a specified storage capacity less than 7.57 L (2 US gal); (d) have a maximum input rating between 14.7 and 73.2 kW (50 000 and 250 000 Btu/h); and (e) are designed to deliver water at a controlled temperature of less than 82 C (180 F). 1.3 The tests specified in this Standard provide a method of comparing performance and efficiency for all applications. The performance ratings are intended to be representative of residential applications. 1.4 In CSA Standards, "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. 1.5 The mandatory requirements of this Standard are those expressed in SI (metric) units. The units given in parentheses are approximate and are for information purposes only. Note: The values in parentheses are from the US Code of Federal Regulations, Title 10, Part 430, Subpart B, Appendix E.