Patented heating elements combined with the Moldatherm fiber insulation and double-walled construction ensure optimum temperature efficiency, fast response, quick heat-up, and rapid cool-down. It features PID temperature control with single-setpoint, programmable 16-segment, or programmable 300 segment control. Digital overtemperature control on select models protects furnace and load from primary control circuit failure. If high limit is reached, it overrides the main controller and shuts off power to furnace.