It has been forecasted for its mounting at the vent of an air conditioning equipment (1), and comprises two independent ducts (2 and 3), one of them with its vent at the upper part of the enclosure and the other with its vent at the lower part of the same enclosure. At the intersection zone between the equipment (1) and the ducts (2 and 3), two couples of grilles (5 and 6) capacitated for occupying two positions are mounted, in order to establish the respective canalizations (10 and 11) for directing cold air or hot air (depending on whether the equipment 1 is producing cold air or producing heat) toward the upper part of the duct (2) or toward the lower part of the duct (3), respectively, establishing is both cases the cold air or hot air return at the lower part of one or other duct.