Duct heaters boost air temperature for any forced air system. It provides additional heat for cold room. Ground Source Heat Pump is provided for boost or backup. Duct heaters resists corrosion/oxidation while protecting resistance coils against contamination. It maximize dielectric strength, heat transfer and life. It permit easy service and reduce downtime. It keeps the wiring cooler and reduces heat loss. It ensures cooler terminations. It accepts an optional type J or K thermocouple for accurate sheath temperature sensing. Duct heaters prevents element sagging or deformation in various mounting positions. It easily bolts to the duct wall. It assures MgO density that eliminates hot spots and meets a wide variety of KW demands.