The utility model relates to a rail vehicle air condensing units and have multiple air conditioning unit of this off -premises station, the off -premises station includes the casing, install the compressor in the casing, gas liquid separator, condensers, room external fan, automatically controlled box, separate a condensation chamber in the casing, press chamber and automatically controlled chamber, condenser and room external fan install at the condensation intracavity, compressor and gas liquid separator install at the press intracavity, automatically controlled box is installed at automatically controlled intracavity, still install the useless device of arranging in automatically controlled chamber or press intracavity, set up the useless mouth that emits into on the casing in automatically controlled chamber or press chamber, set up useless discharge port on the casing in automatically controlled chamber and/or press chamber. The utility model discloses the just useless device of arranging is installed in the off -premises station, need not in addition on the automobile body useless row of devices such as the useless exhaust fan of installation, makes the structure compacter, and in addition in give up rows, usable useless airing exhaust is lowered the temperature for the parts such as compressor of the electric control element in automatically controlled chamber and press intracavity, not only can the energy saving, still be favorable to improving the reliability that electric control element worked.