BS 6644:2011

This standard BS 6644:2011 Specification for the installation and maintenance of gas-fired hot water boilers of rated inputs between 70 kW (net) and 1.8 MW (net) (2nd and 3rd family gases) is classified in these ICS categories:

• 91.140.65 Water heating equipment

This British Standard specifies requirements for the installation, including design, inspection, commissioning and maintenance, of gas-fired hot water boilers of net rated heat inputs exceeding 70 kW but not exceeding a net heat input of 1.8 MW. Groups of boilers with individual net heat inputs of 70 kW or less, but with aggregate net heat inputs in excess of 70 kW, are also covered.

This British Standard is applicable to the installation of boilers that are designed to utilize normally distributed gases of Group H of the second family (e.g. natural gas), and gases of Group P (e.g. propane) and Group B (e.g. butane) of the third family. For the purposes of this installation standard, LPG/air mixtures are regarded as third family gases.

This British Standard is applicable to the installation of the following gas-fired hot water boilers:

1. boilers supplied as a complete assembly and conforming to BS EN 656 or BS 5978 (all parts);

2. boilers supplied as a complete assembly and used in multiple boiler installations where the total net heat input exceeds 70 kW and conforming to BS EN 297, BS EN 483 or BS EN 677;

3. boilers and burners delivered separately and assembled on site, comprising:

   1. a boiler shell conforming to BS EN 303‑1, BS EN 12952 (all parts), BS EN 12953 (all parts), BS 779, BS 855 or BS 2790;

   2. a burner conforming to BS EN 676;

   3. an assembly conforming to BS EN 303‑3 or BS 5978‑1 and BS 5978‑3.

      NOTE 1 It is recognized that the design, inspection and commissioning require different levels of competence (see 4.1 and 4.2). Where all of these tasks are performed by same person, that person has to have the necessary levels of competence for each task.

      NOTE 2 Although this British Standard does not contain any requirements for industrial processes, the general principles can be applied.

      NOTE 3 The general principles of this British Standard with respect to hot water circuits can be used for boilers exceeding 1.8 MW net heat input (2 MW gross heat input). For installations exceeding 1.8 MW net heat input see IGEM/UP/10 [18].

      NOTE 4 The ratio of gross to net heat input is approximately 1.11:1 for Group H (natural gas), 1.09:1 for Group P (propane) and 1.08:1 for Group B (butane).

It is also applicable to installations that have been converted from burning other fuels to gas-firing.

This British Standard is not applicable to:

1. the installation of any heating or hot water supply system associated with the boiler installation;

2. the installation of gas cushion systems (non diaphragm expansion vessels) intended to pressurize the hot water circuit; or

3. installations in hazardous areas, as defined in The Dangerous Substances and Explosive Atmospheres Regulations (DSEAR) 2002 [16], other than those classified as Zone 2 NE, guidance on which is given in IGEM/SR/25 [19] and IGEM/UP/16 [20].