New Jersey Statutes Title 45. Professions and Occupations 45 § 16A-27

a. Nothing in this act  1 shall be construed to prevent licensed master plumbers from engaging in the installation, maintenance and repair of: power boiler systems, hot water and steam heating systems, fire tube and water tube boilers, pressure steam and hot water boilers, space heaters, unit heaters, and appurtenances utilizing electricity, fossil fuel or solar energy; steam, hot water and chilled water pipe, condensate piping, valves, fittings, burners and piping, expansion tanks, pumps, gauges on the load side of a meter; thermostatic controls; or natural or manufactured gas piping; or the installation, maintenance or connection of: pneumatic controls and control piping for the control of air, liquid or gas temperatures, radiators, convectors, cabinet unit heaters, fan coil units, air handlers utilizing hydronic coils, mechanical ventilation for radon mitigation, humidifiers, flues and patented chimneys; or of pneumatic controls and control piping of automatic oil, gas or coal burning equipment, gasoline or diesel oil dispensing equipment and in replacement cases only, the connection thereof of the wiring from a dedicated electrical service disconnect box of adequate size to accommodate the equipment and controls, and the testing and balancing of hydronic systems; or the installation, repair, testing or closure of waste oil underground storage tanks.

b. Nothing in this act shall be construed to prevent licensed electrical contractors from engaging in the installation of: electrical resistance heating equipment and ventilation equipment with the exhaust duct not exceeding 60 square inches in area, or in commercial applications the connection sleeve between a roof-top mounted exhaust fan and its central connecting register, provided that this connection sleeve is not more than 15 inches in length or the length necessary to penetrate a roof or other similar openings; and the maintenance and repair of the electrical sections of any equipment used for heating, ventilating, air conditioning or refrigeration.