管道、供暖和空调系统的安装

This class includes the installation of plumbing, heating and air-conditioning systems, including additions, alterations, maintenance and repair. This class includes: - installation in buildings or other construction projects of: * heating systems (electric, gas and oil) * furnaces, cooling towers * non-electric solar energy collectors * plumbing and sanitary equipment * ventilation, refrigeration or air-conditioning equipment and ducts * gas fittings * steam piping * fire sprinkler systems * lawn sprinkler systems - duct work installation

This class excludes: - installation of electric baseboard heating, see 4321