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