Abstract: A heater is provided that has a temperature sensing control system which can be used for both temperature control and over-temperature protection against element burnout. The temperature control system is comprised of an inlet temperature sensing assembly positioned at the inlet to the heater element and an exit thermocouple positioned in the exit end of the heater element. The exit thermocouple may be used for control the heater temperature and provide over-temperature protection. The inlet temperature sensing assembly is used to detect low or no air flow conditions which could lead to heater element failure.

Abstract: A fluid heater comprises a first elongated cylindrical housing having a first diameter, a first end for heated fluid exit, a second end for fluid entrance, and a longitudinal axis. An elongated cylindrical airflow member is fixedly positioned within the housing and coaxial therewith. The airflow member has a second diameter and has a length less than the length of the housing and terminates before the first end. A heating element has a third diameter and is positioned coaxially within the airflow member and is fixed therein. A baffle tube is fixed to the first end in a fluid-tight manner, this baffle tube having a diameter greater than the third diameter of the heating element and less than the diameter of the airflow member. The baffle tube surrounds the forward portion 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.