“Foreign to the electrical installation” means equipment that does not serve the electrical equipment, or a dedicated room or space provided for the electrical equipment. Fire protection sprinkler system branch piping serving the electrical room or the area in which the electrical equipment is installed is not considered “foreign.” Neither is ductwork installed in an electrical room for the purpose of ventilating or cooling that space. A sprinkler main or riser for another part of the building or a duct that passes through an electrical room to serve another space would not be permitted.