This invention provides an improved heating apparatus for controlling the temperatures of the resin melt that is pressure fed to a molding cavity comprising a heating jacket 30 comprising the concentric tubular elements; a copper sheath 32 having an inside surface 34 and an outer surface 36, a retainer sleeve 40 and coiled heating element 42 sandwiched between the sheath 32 and the retainer sleeve 40. The inside surface of the sheath 32 is formed with at least one circumferential groove 38 which provides an insulating air gap so that a lesser amount of heat is conducted to the central portion of the heating jacket 30 thereby creating three distinct temperature zones. The outer surface 23 of the nozzle 22 is provided with a longitudinal groove 46 extending down its outside surface between the sheath 32 and the nozzle housing 22 for the hot runner conduit 24. A thermocouple sensor cable 52 is received in the longitudinal groove so that the thermocouple sensor 50 is strategically positioned adjacent the gate well section 28 to maintain the temperature of the resin melt entering the cavity.