Abstract: In a chromatography system of the type including an oven for the chromatographic column, and an electric heater for controllably heating the oven, an improved system is disclosed for controllably opening and closing the oven door to enable a fully controlled heat leak, thereby to stabilize the oven temperature at a desired set point. A signal, which is indicative by first or second conditions of an oven temperature above or below the set point, is generated. A heater power control responsive to one of the signal conditions can effect heating of the oven. A bi-directional door motor and actuator means is provided for opening and closing the oven door over a prescribed operating range, and this means is enabled to operate for a predetermined period upon the signal in its first or second condition departing from preset threshold values for a predetermined period, in consequence of which the opening or closing of the oven door is effected in incremental steps.