Abstract: A forced gas electric heater has a serpentine heating element disposed within a cylindrical glass tube. Infrared radiation emanating from the heating element enters the glass tube whereby part of the infrared radiation is directed within the wall of the glass tube to the edge of the glass tube. An infrared sensor is in line of sight with the edge of the glass tube. The infrared sensor senses the hot spot temperature of the heating element and, together with a controller, limits the maximum hot spot temperature of the heating element.

Abstract: An electric air or gas heater includes a plurality of equal diameter elongated linear serpentine resistive wire heating elements circularly arranged in parallel about a common axis and disposed within a cylindrical chamber having separable air or gas entrance and exit sections at its opposite ends. Each heating element is disposed in a close-fitting ceramic or quartz tube. The tubes are supported by discs at the opposite ends of the chamber which block air or gas flow outside the cross-sectional area of the tubes. Each heating element has a ceramic cylinder extending through the center thereof through which a wire for electrically connecting adjacent pairs of heating elements extends.

Abstract: A forced gas electric heater has a serpentine heating element in series with a preheat coil. Gas to be heated first flows through the preheat coil before flowing through the serpentine heating element. A thermistor is disposed between two adjacent turns of the preheat coil. The thermistor controls the "on" time of a solid state power control device which is in series with the preheat coil and the serpentine heating element.