Describes the constructional requirements and testing of thermostatically controlled cast iron and steel gravity feed central heating boilers with rated outputs up to 44 kW designed for burning small anthracite. Applies to boilers with integral fuel storage fed by gravity from storage space to the fuelbed. Ash is normally removed as clinker. Includes definitions, rated output, fuel capacity, combustion controls, chimney, container for incombustible residue, operating tools, fuel outlet, quality of material, thickness of steel boiler shells, boiler shell tappings, boiler fire and water tubes, draining, test tapping thermostat, design, finish, assembly, installation, operation and maintenance and marking.