Test method for determining the performance of combined space and water heating systems (combos)

1.1
This Standard provides a method for measuring annual fireplace efficiency. 

1.2
This Standard applies to vented gas fireplaces meeting the requirements of ANSI Z21.50/CSA 2.22 and to vented gas fireplace heaters approved to ANSI Z21.88/CSA 2.33 that use natural gas or propane. 

1.3
This Standard does not apply to decorative fireplaces meeting the requirements of ANSI Z21.60/CSA 2.26. 

1.4
This Standard includes 

a) a test method for cyclic and part-load performance
b) methods for interpolating and extrapolating test data and 
c) calculation procedures for establishing seasonal performance. 

1.5
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. 

1.6
The values given in SI (metric) are the units of record for the purposes of this Standard. The values given in parentheses are for information and comparison only.