This British Standard specifies requirements for the selection, installation, inspection and commissioning of gas-fired water-heating appliances of rated net input not exceeding 70 kW, which supply hot water for domestic purposes. It applies to appliances which use 1st, 2nd or 3rd family gases.
This British Standard does not apply to hot water supply systems in multiple dwellings supplied from a central source.
NOTE 1 In this standard, heat input is expressed in terms of net calorific values (CV) unless stated otherwise. The ratio of gross to net heat input is approximately 1.11: 1 for natural gas, 1.09: 1 for propane and 1.08:1 for butane.
NOTE 2 It is essential that persons carrying out the installation of any gas appliance be competent to do so. Annex A gives information about the legal requirements which relate to approved installers of gas appliances.