The present invention wants to create an electric heating device handling these contradictory requirements as best as possible.

For the solution the present invention suggests that the heating rib is provided with a heating rib frame which comprises at least one window. The window thus forms a penetration between the interior of the heating rib frame serving the accommodation of the PTC heating element, and the exterior surface against which the medium to be heated normally flows. According to the invention the insulation layer is exposed in this window so that the heat generated by the PTC element has just to be passed through the strip conductor and through the insulation layer before said heat can be dissipated by way of convection on the surface of the electrical insulation layer. The heat conduction paths are shortened accordingly. The electrical performance of the FTC element can thereby be exploited in the best way possible.

The heating rib frame is preferably made from a material of good thermal conductivity. It may be formed from metal or a heat-conducting plastic improved by way of thermally conductive fillers. The heating rib frame encloses the PTC heating element, so that the FTC element is safely housed with respect to the environment. The exterior surfaces of the heating ribs that are exposed in the circulation chamber are thus exclusively formed either by the heating rib frame or by the exterior surface of the insulation layer.